Kohler CH20, CH18-750, CH750, CH740, CH23 User Manual

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COMMAND CH18-750

HORIZONTAL CRANKSHAFT

SERVICE MANUAL

Section 1. Safety and General Information ............................................................................

Section 2. Special Tools ..........................................................................................................

Section 3. Troubleshooting .....................................................................................................

Section 4. Air Cleaner and Air Intake System ........................................................................

Section 5. Fuel System and Governor....................................................................................

Section 5A. LPG Fuel Systems ...............................................................................................

Section 5B. Electronic Fuel Injection (EFI) Fuel System ......................................................

Section 6. Lubrication System ................................................................................................

Section 7. Retractable Starter .................................................................................................

Section 8. Electrical System and Components .....................................................................

Section 9. Disassembly ...........................................................................................................

Section 10. Inspection and Reconditioning ...........................................................................

Section 11. Reassembly...........................................................................................................

Section 12. Clutch ....................................................................................................................

Safety and General Information

Section 1

Safety and General Information

Safety Precautions

To ensure safe operation please read the following statements and understand their meaning. Also refer to your equipment manufacturer's manual for other important safety information. This manual contains safety precautions which are explained below. Please read carefully.

WARNING

Warning is used to indicate the presence of a hazard that can cause severe personal injury, death, or substantial property damage if the warning is ignored.

CAUTION

Caution is used to indicate the presence of a hazard that will or can cause minor personal injury or property damage if the caution is ignored.

Section 1

NOTE

Note is used to notify people of installation, operation, or maintenance information that is important but not hazard-related.

For Y our Safety!

These precautions should be followed at all times. Failure to follow these precautions could result in injury to yourself and others.

WARNING

Accidental Starts can cause severe injury or death.

Disconnect and ground spark plug leads before servicing.

Accidental Starts!

Disabling engine. Accidental starting can cause severe injury or death.

Before working on the engine or equipment, disable the engine as follows:

1) Disconnect the spark plug lead(s). 2) Disconnect negative (-) battery cable from battery.

WARNING

Rotating Parts can cause severe injury.

Stay away while engine is in operation.

Rotating Parts!

Keep hands, feet, hair, and clothing away from all moving parts to prevent injury. Never operate the engine with covers, shrouds, or guards removed.

Hot Parts can cause severe burns.

Do not touch engine while operating or just after stopping.

Hot Parts!

Engine components can get extremely hot from operation. To prevent severe burns, do not touch these areas while the engine is running - or immediately after it is turned off. Never operate the engine with heat shields or guards removed.

WARNING

1.1

Section 1 Safety and General Information

WARNING

Explosive Fuel can cause fires and severe burns.

Do not fill the fuel tank while the engine is hot or running.

Explosive Fuel!

Gasoline is extremely flammable and its vapors can explode if ignited. Store gasoline only in approved containers, in well ventilated, unoccupied buildings, away from sparks or flames. Do not fill the fuel tank while the engine is hot or running, since spilled fuel could ignite if it comes in contact with hot parts or sparks from ignition. Do not start the engine near spilled fuel. Never use gasoline as a cleaning agent.

WARNING

WARNING WARNING

Carbon Monoxide can cause severe nausea, fainting or death.

Avoid inhaling exhaust fumes, and never run the engine in a closed building or confined area.

Lethal Exhaust Gases!

Engine exhaust gases contain poisonous carbon monoxide. Carbon monoxide is odorless, colorless, and can cause death if inhaled. Avoid inhaling exhaust fumes, and never run the engine in a closed building or confined area.

WARNING

Uncoiling Spring can cause severe injury.

Wear safety goggles or face protection when servicing retractable starter.

Explosive Gas can cause fires and severe acid burns.

Charge battery only in a well ventilated area. Keep sources of ignition away.

Explosive Gas!

Batteries produce explosive hydrogen gas while being charged. To prevent a fire or explosion, charge batteries only in well ventilated areas. Keep sparks, open flames, and other sources of ignition away from the battery at all times. Keep batteries out of the reach of children. Remove all jewelry when servicing batteries.

Before disconnecting the negative (-) ground cable, make sure all switches are OFF. If ON, a spark will occur at the ground cable terminal which could cause an explosion if hydrogen gas or gasoline vapors are present.

Cleaning Solvents can cause severe injury or death.

Use only in well ventilated areas away from ignition sources.

Flammable Solvents!

Carburetor cleaners and solvents are extremely flammable. Keep sparks, flames, and other sources of ignition away from the area. Follow the cleaner manufacturer’s warnings and instructions on its proper and safe use. Never use gasoline as a cleaning agent.

1.2

Spring Under T ension!

Retractable starters contain a powerful, recoil spring that is under tension. Always wear safety goggles when servicing retractable starters and carefully follow instructions in the "Retractable Starter" Section 7 for relieving spring tension.

CAUTION

Electrical Shock can cause injury.

Do not touch wires while engine is running.

Electrical Shock!

Never touch electrical wires or components while the engine is running. They can be sources of electrical shock.

Engine Identification Numbers

When ordering parts, or in any communication involving an engine, always give the Model, Specification and Serial Numbers, including letter suffixes if there are any.

The engine identification numbers appear on a decal, or decals, affixed to the engine shrouding. See Figure 1-1. An explanation of these numbers is shown in Figure 1-2.

Section 1

Safety and General Information

Identification Decal

Figure 1-1. Engine Identification Decal Location.

A. Model No.

Command Engine

Horizontal Crankshaft

Horsepower

17 = 17 HP 18 = 18 HP 20 = 20 HP 22 = 22 HP 23 = 23 HP 25 = 25 HP 26 = 26 HP

B. Spec. No.

Engine Model Code Code Model

62 CH18 64 CH20 66 CH22 (624 cc) 68 CH25 76 CH22/23 (674 cc) 78 CH26

C H 18 S

62500

Numerical Designation

730 740 745 750

Variation of Basic Engine

Version Code

S = Electric Start

CH730-0001 CH740-0001 CH745-0001 CH750-0001

Complete Spec Number (Incorporating Model No. with V ariation No. of Basic Spec.)

C. Serial No.

Year Manufactured Code Code Year

21 1991 22 1992 23 1993 24 1994 25 1995 26 1996 27 1997 28 1998 29 1999

Figure 1-2. Explanation of Engine Identification Numbers.

3305810334

Factory Code

Code Year

30 2000 31 2001 32 2002 33 2003 34 2004 35 2005 36 2006 37 2007

1.3

Section 1 Safety and General Information

Oil Recommendations

Using the proper type and weight of oil in the crankcase is extremely important. So is checking oil daily and changing oil regularly. Failure to use the correct oil, or using dirty oil, causes premature engine wear and failure.

Oil Type

Use high-quality detergent oil of API (American Petroleum Institute) Service Class SG, SH, SJ or higher.

Select the viscosity based on the air temperature at the time of operation as shown in the following table.

*Use of synthetic oil having 5W-20 or 5W-30 rating is acceptable, up to 4°C (40°F). **Synthetic oils will provide better starting in

extreme cold (below -23°C (-10°F).

Refer to Section 6 - “Lubrication System” for detailed procedures on checking the oil, changing the oil and changing the oil filter.

Fuel Recommendations

WARNING: Explosive Fuel!

Gasoline is extremely flammable and its vapors can explode if ignited. Before servicing the fuel system, make sure there are no sparks, open flames or other sources of ignition nearby as these can ignite gasoline vapors. Disconnect and ground the spark plug leads to prevent the possibility of sparks from the ignition system.

General Recommendations

Purchase gasoline in small quantities and store in clean, approved containers. A container with a capacity of 2 gallons or less with a pouring spout is recommended. Such a container is easier to handle and helps eliminate spillage during refueling.

Do not use gasoline left over from the previous season, to minimize gum deposits in your fuel system and to ensure easy starting.

Do not add oil to the gasoline.

NOTE: Using other than service class SG, SH, SJ or

higher oil or extending oil change intervals longer than recommended can cause engine damage.

NOTE: Synthetic oils meeting the listed

classifications may be used with oil changes performed at the recommended intervals. However, to allow piston rings to properly seat, a new or rebuilt engine should be operated for at least 50 hours using standard petroleum based oil before switching to synthetic oil.

A logo or symbol on oil containers identifies the API service class and SAE viscosity grade. See Figure 1-3.

Do not overfill the fuel tank. Leave room for the fuel to expand.

Fuel Type

For best results, use only clean, fresh, unleaded gasoline with a pump sticker octane rating of 87 or higher. In countries using the Research method, it should be 90 octane minimum.

Unleaded gasoline is recommended as it leaves less combustion chamber deposits and reduces harmful exhaust emissions. Leaded gasoline is not recommended and must not be used on EFI engines, or on other models where exhaust emissions are regulated.

Gasoline/Alcohol blends

Gasohol (up to 10% ethyl alcohol, 90% unleaded gasoline by volume) is approved as a fuel for Kohler engines. Other gasoline/alcohol blends are not approved.

Gasoline/Ether blends

Methyl Tertiary Butyl Ether (MTBE) and unleaded gasoline blends (up to a maximum of 15% MTBE by volume) are approved as a fuel for Kohler engines. Other gasoline/ether blends are not approved.

Figure 1-3. Oil Container Logo.

1.4

Periodic Maintenance Instructions

Section 1

Safety and General Information

WARNING: Accident al Start s!

Disabling engine. Accidental starting can cause severe injury or death. Before working on the engine or equipment, disable the engine as follows: 1) Disconnect the spark plug lead(s). 2) Disconnect negative (-) battery cable from battery.

Maintenance Schedule

These required maintenance procedures should be performed at the frequency stated in the table. They should also be included as part of any seasonal tune-up.

Maintenance RequiredFrequency

• Fill fuel tank Section 5

Daily or Before

Starting Engine

Every 25 Hours

Every 100 Hours

Every 200 Hours

Every 250 Hours

Annually or

Every 500 Hours Every 500 Hours

Every 1500 Hours

¹Perform these maintenance procedures more frequently under extremely dusty, dirty conditions. ²Only requried for Denso starters. Not necessary on Delco starters. Have a Kohler Engine Service Dealer perform this service. ³Cleanout Kits 25 755 20-S (black) or 25 755 21-S (gold) allow cooling areas to be cleaned without removing shrouds.

• Check oil level. Section 6

• Check air cleaner for dirty1, loose, or damaged parts. Section 4

• Check air intake and cooling areas, clean as necessary1. Section 4

• Service precleaner element1. Section 4

• Replace air cleaner element1. Section 4

• Change oil. (More frequently under severe conditions.) Section 6

• Remove cooling shrouds and clean cooling areas

• Check oil cooler fins, clean as necessary (if equipped). Section 6

• Check spark plug condition and gap. Section 8

• Change oil filter. Section 6

• Change fuel filter (carbureted engines). Section 5

• Replace heavy-duty air cleaner element and check inner element1. Section 4

• Have bendix starter drive serviced2. Section 8

• Have solenoid shift starter disassembled and cleaned2. Section 8

• Have crankshaft splines lubricated2. Section 2

• Replace fuel filter1 (EFI engines). Section 5B

1,3

. Section 4

Refer to:

Storage

If the engine will be out of service for two months or more, use the following storage procedure:

1. Clean the exterior surfaces of the engine. On Electronic Fuel Injected (EFI) engines, avoid spraying water at the wiring harness or any of the electrical components.

2. Change the oil and oil filter while the engine is still warm from operation. See “Change Oil and Oil Filter” in Section 6.

3. The fuel system must be completely emptied, or the gasoline must be treated with a stabilizer to prevent deterioration. If you choose to use a stabilizer, follow the manufacturer’s recommendations, and add the correct amount for the capacity of the fuel system.

Fill the fuel tank with clean, fresh gasoline. Run the engine for 2 to 3 minutes to get stabilized fuel into the rest of the system. Close the fuel shut-off valve when the unit is being stored or transported.

To empty the system, run the engine until the tank and the system are empty.

4. Remove the spark plugs and add one tablespoon of engine oil into each spark plug hole. Install the spark plugs, but do not connect the plug leads. Crank the engine two or three revolutions.

5. On equipment with an EFI engine, disconnect the battery or use a battery minder to keep the battery charged during storage.

6. Store the engine in a clean, dry place.

1.5

Section 1 Safety and General Information

Dimensions in millimeters. Inch equivalents shown in [ ].

Figure 1-4. Typical Engine Dimensions CH Series with Standard Flat Air Cleaner.

1.6

Section 1

Safety and General Information

Dimensions in millimeters. Inch equivalents shown in [ ].

Figure 1-5. T ypical Engine Dimensions CH EFI Series with Heavy-Duty Air Cleaner.

1.7

Section 1 Safety and General Information

General Specifications¹

Power (@ 3600 RPM, exceeds Society of Automotive Engineers-Small Engine Test Code J1940.)

CH18 ........................................................................................................................................ 13.4 kW (18 HP)

CH20 ........................................................................................................................................ 14.9 kW (20 HP)

CH22 ........................................................................................................................................ 16.4 kW (22 HP)

CH23 ........................................................................................................................................ 17.2 kW (23 HP)

CH25, CH730 .......................................................................................................................... 18.6 kW (25 HP)

CH26 ........................................................................................................................................ 19.4 kW (26 HP)

CH740 ...................................................................................................................................... 20.1 kW (27 HP)

CH745 ...................................................................................................................................... 20.9 kW (28 HP)

CH750 ...................................................................................................................................... 22.3 kW (30 HP)

Peak Torque

CH18 @ 2200 RPM ................................................................................................................. 43.6 N·m (32.2 ft. lb.)

CH20 @ 2400 RPM ................................................................................................................. 44.3 N·m (32.7 ft. lb.)

CH22 @ 2400 RPM ................................................................................................................. 49.1 N·m (36.2 ft. lb.)

CH23 @ 2400 RPM ................................................................................................................. 54.1 N·m (37.9 ft. lb.)

CH25 @ 2200 RPM ................................................................................................................. 54.0 N·m (39.5 ft. lb.)

CH730 @ 2400 RPM ............................................................................................................... 55.4 N·m (40.9 ft. lb.)

CH26 @ 2800 RPM ................................................................................................................. 54.2 N·m (40.0 ft. lb.)

CH740 @ 2400 RPM ............................................................................................................... 57.3 N·m (42.3 ft. lb.)

CH745 @ 2600 RPM ............................................................................................................... 57.9 N·m (42.7 ft. lb.)

CH750 @ 2400 RPM ............................................................................................................... 64.4 N·m (47.5 ft. lb.)

Bore

CH18, CH20, CH22 (624 cc) .................................................................................................. 77 mm (3.03 in.)

CH22/23 (674 cc) .................................................................................................................... 80 mm (3.15 in.)

CH25, CH26, CH730-750 ....................................................................................................... 83 mm (3.27 in.)

Stroke

CH18-745 ................................................................................................................................ 67 mm (2.64 in.)

CH750 ...................................................................................................................................... 69 mm (2.7 in.)

Displacement

CH18, CH20, CH22 (624 cc) .................................................................................................. 624 cc (38 cu. in.)

CH22/23 (674 cc) .................................................................................................................... 674 cc (41 cu. in.)

CH25, CH26, CH730-745 ....................................................................................................... 725 cc (44 cu. in.)

CH750 ...................................................................................................................................... 755 cc (46 cu. in.)

Compression Ratio

CH18, CH20, CH22/23 ........................................................................................................... 8.5:1

CH25, CH26, CH730-745 ....................................................................................................... 9.0:1

CH750 ...................................................................................................................................... 9.4:1

Dry Weight

CH18, CH20, CH22/23 ........................................................................................................... 41 kg (90 lb.)

CH25, CH26, CH730-745 ....................................................................................................... 43 kg (94 lb.)

CH750 ...................................................................................................................................... 48 kg (105 lb.)

Oil Capacity (w/filter) - approximate,

determined by oil filter and oil cooler used ............................................................................. 1.6-1.8 L (1.7-1.9 U.S. qt.)

¹Values are in Metric units. Values in parentheses are English equivalents. Lubricate threads with engine oil

prior to assembly.

1.8

General Specifications¹ cont.

Section 1

Safety and General Information

Angle of Operation - Maximum (At Full Oil Level) All Directions ................... 25°

Blower Housing and Sheet Metal

M5 Fasteners Torque ................................................................................................ 6.2 N·m (55 in. lb.) into new holes

4.0 N·m (35 in. lb.) into used holes

M6 Fasteners Torque ................................................................................................ 10.7 N·m (95 in. lb.) into new holes

7.3 N·m (65 in. lb.) into used holes

Rectifier-Regulator Fastener Torque ................................................................... 1.4 N·m (12.6 in. lb.)

Camshaft

End Play (With Shim) ............................................................................................ 0.076/0.127 mm (0.0030/0.0050 in.)

Running Clearance ................................................................................................. 0.025/0.063 mm (0.0010/0.0025 in.)

Bore I.D.

New .................................................................................................................. 20.000/20.025 mm (0.7874/0.7884 in.)

Max. Wear Limit............................................................................................. 20.038 mm (0.7889 in.)

Camshaft Bearing Surface O.D.

New .................................................................................................................. 19.962/19.975 mm (0.7859/0.7864 in.)

Max. Wear Limit............................................................................................. 19.959 mm (0.7858 in.)

Carburetor and Intake Manifold

Intake Manifold Mounting Fastener Torque

Torque in Two Stages ..................................................................................... first to 7.4 N·m (66 in. lb.)

finally to 9.9 N·m (88 in. lb.)

Carburetor Mounting Screw Torque M6 ............................................................ 6.2-7.3 N·m (55-65 in. lb.)

Adapter (for Heavy Duty Air Cleaner) Mounting Fastener Torque ................ 7.3 N·m (65 in. lb.)

Connecting Rod

Cap Fastener Torque (torque in increments)

8 mm straight shank ............................................................................................ 22.7 N·m (200 in. lb.)

8 mm step-down .................................................................................................. 14.7 N·m (130 in. lb.)

6 mm straight shank ............................................................................................ 11.3 N·m (100 in. lb.)

Connecting Rod-to-Crankpin Running Clearance

New .................................................................................................................. 0.030/0.055 mm (0.0012/0.0022 in.)

Max. Wear Limit............................................................................................. 0.070 mm (0.0028 in.)

Connecting Rod-to-Crankpin Side Clearance .................................................... 0.26/0.63 mm (0.0102/0.0248 in.)

Connecting Rod-to-Piston Pin Running Clearance........................................... 0.015/0.028 mm (0.0006/0.0011 in.)

Piston Pin End I.D.

New .................................................................................................................. 17.015/17.023 mm (0.6699/0.6702 in.)

Max. Wear Limit............................................................................................. 17.036 mm (0.6707 in.)

¹Values are in Metric units. Values in parentheses are English equivalents. Lubricate threads with engine oil

prior to assembly.

1.9

Section 1 Safety and General Information

Crankcase

Governor Cross Shaft Bore I.D.

6 mm Shaft

New .................................................................................................................. 6.025/6.050 mm (0.2372/0.2382 in.)

Max. Wear Limit............................................................................................. 6.063 mm (0.2387 in.)

8 mm Shaft

New .................................................................................................................. 8.025/8.075 mm (0.3159/0.3179 in.)

Max. Wear Limit............................................................................................. 8.088 mm (0.3184 in.)

Breather Cover Fastener Torque .......................................................................... 7.3 N·m (65 in. lb.)

Oil Drain Plug Torque ............................................................................................ 13.6 N·m (10 ft. lb.)

Closure Plate

Closure Plate Fastener Torque .............................................................................. 24.4 N·m (216 in. lb.)

Crankshaft

End Play (Free) ........................................................................................................ 0.070/0.590 mm (0.0028/0.0230 in.)

End Play (With Thrust Bearing Components) ................................................... 0.070/0.270 mm (0.0028/0.0100 in.)

Except CH25 Engines Below Serial No. 2403500008 .......................................... 0.050/0.750 mm (0.0020/0.0295 in.)

Crankshaft Bore (In Crankcase)

New .................................................................................................................. 40.965/41.003 mm (1.6128/1.6143 in.)

Max. Wear Limit............................................................................................. 41.016 mm (1.6148 in.)

Crankshaft to Sleeve Bearing (Crankcase)

Running Clearance - New ............................................................................ 0.03/0.09 mm (0.0012/0.0035 in.)

Crankshaft Bore (In Closure Plate) - New .......................................................... 40.987/40.974 mm (1.6136/1.6131 in.)

Crankshaft Bore (In Closure Plate)-to-Crankshaft

Running Clearance - New ............................................................................ 0.039/0.074 mm (0.0015/0.0029 in.)

Flywheel End Main Bearing Journal

O.D. - New ....................................................................................................... 40.913/40.935 mm (1.6107/1.6116 in.)

O.D. - Max. Wear Limit .................................................................................. 40.84 mm (1.608 in.)

Max. Taper ....................................................................................................... 0.022 mm (0.0009 in.)

Max. Out-of-Round ........................................................................................ 0.025 mm (0.0010 in.)

Closure Plate End Main Bearing Journal

O.D. - New ....................................................................................................... 40.913/40.935 mm (1.6107/1.6116 in.)

O.D. - Max. Wear Limit .................................................................................. 40.84 mm (1.608 in.)

Max. Taper ....................................................................................................... 0.022 mm (0.0009 in.)

Max. Out-of-Round ........................................................................................ 0.025 mm (0.0010 in.)

Connecting Rod Journal

O.D. - New ....................................................................................................... 35.955/35.973 mm (1.4156/1.4163 in.)

O.D. - Max. Wear Limit .................................................................................. 35.94 mm (1.415 in.)

Max. Taper ....................................................................................................... 0.018 mm (0.0007 in.)

Max. Out-of-Round ........................................................................................ 0.025 mm (0.0010 in.)

1.10

Section 1

Safety and General Information

Crankshaft cont.

Crankshaft T.I.R.

PTO End, Crank in Engine ............................................................................. 0.279 mm (0.0110 in.)

Entire Crank, in V-Blocks .............................................................................. 0.10 mm (0.0039 in.)

Cylinder Bore

Cylinder Bore I.D.

New - CH18, CH20, CH22 (624 cc) ............................................................... 77.000/77.025 mm (3.0315/3.0325 in.)

New - CH22/23 (674 cc) ................................................................................. 80.000/80.025 mm (3.1496/3.1506 in.)

New - CH25, CH26, CH730-750 ................................................................... 82.988/83.013 mm (3.2672/3.2682 in.)

Max. Wear Limit - CH18, CH20, CH22 (624 cc) .......................................... 77.063 mm (3.0340 in.)

Max. Wear Limit - CH22/23 (674 cc) ............................................................ 80.065 mm (3.1522 in.)

Max. Wear Limit - CH25, CH26, CH730-750 .............................................. 83.051 mm (3.2697 in.)

Max. Out-of-Round ........................................................................................ 0.12 mm (0.0047 in.)

Max. Taper ....................................................................................................... 0.05 mm (0.0020 in.)

Cylinder Head

Cylinder Head Fastener Torque

Hex Flange Nut - Torque in Two Stages ...................................................... first to 16.9 N·m (150 in. lb.)

finally to 33.9 N·m (300 in. lb.)

Head Bolt - Torque in Two Stages ................................................................ first to 22.6 N·m (200 in. lb.)

finally to 41.8 N·m (370 in. lb.)

Max. Out-of-Flatness .............................................................................................. 0.076 mm (0.003 in.)

Rocker Arm Screw Torque .................................................................................... 11.3 N·m (100 in. lb.)

Fan/Flywheel

Fan Fastener Torque ............................................................................................... 9.9 N·m (88 in. lb.)

Flywheel Retaining Screw Torque ....................................................................... 66.4 N·m (49 ft. lb.)

Governor

Governor Cross Shaft-to-Crankcase Running Clearance

6 mm Shaft............................................................................................................. 0.013/0.075 mm (0.0005/0.0030 in.)

8 mm Shaft............................................................................................................. 0.025/0.126 mm (0.0009/0.0049 in.)

Governor Cross Shaft O.D.

6 mm Shaft

New .................................................................................................................. 5.975/6.012 mm (0.2352/0.2367 in.)

Max. Wear Limit............................................................................................. 5.962 mm (0.2347 in.)

8 mm Shaft

New .................................................................................................................. 7.949/8.000 mm (0.3129/0.3149 in.)

Max. Wear Limit............................................................................................. 7.936 mm (0.3124 in.)

Governor Gear Shaft-to-Governor Gear Running Clearance ......................... 0.015/0.140 mm (0.0006/0.0055 in.)

Governor Gear Shaft O.D.

New .................................................................................................................. 5.990/6.000 mm (0.2358/0.2362 in.)

Max. Wear Limit............................................................................................. 5.977 mm (0.2353 in.)

Governor Lever Nut Torque ................................................................................. 6.8 N·m (60 in. lb.)

1.11

Section 1 Safety and General Information

Ignition

Spark Plug Type (Champion®or Equivalent) ..................................................... RC12YC, XC12YC, or Platinum 3071

Spark Plug Gap ....................................................................................................... 0.76 mm (0.030 in.)

Spark Plug Torque .................................................................................................. 24.4-29.8 N·m (18-22 ft. lb.)

Ignition Module Air Gap ....................................................................................... 0.28/0.33 mm (0.011/0.013 in.)

Ignition Module Fastener Torque ......................................................................... 4.0-6.2 N·m (35-55 in. lb.)

Speed Sensor Air Gap (EFI engines) ..................................................................... 1.50 ± 0.25 mm (0.059 ± 0.010 in.)

Muffler

Muffler Retaining Nut Torque .............................................................................. 24.4 N·m (216 in. lb.)

Oil Filter

Oil Filter Torque ...................................................................................................... 3/4-1 turn after gasket contact

Oil Cooler

Oil Cooler/Adapter Nipple Torque ...................................................................... 27 N·m (20 ft. lb.)

Piston, Piston Rings, and Piston Pin

Piston-to-Piston Pin Running Clearance ............................................................ 0.006/0.017 mm (0.0002/0.0007 in.)

Piston Pin Bore I.D.

New .................................................................................................................. 17.006/17.012 mm (0.6695/0.6698 in.)

Max. Wear Limit............................................................................................. 17.025 mm (0.6703 in.)

Piston Pin O.D.

New .................................................................................................................. 16.995/17.000 mm (0.6691/0.6693 in.)

Max. Wear Limit............................................................................................. 16.994 mm (0.6691 in.)

Top Compression Ring-to-Groove Side Clearance

CH18, CH20, CH22 (624 cc) ........................................................................... 0.040/0.080 mm (0.0016/0.0031 in.)

CH22/23 (674 cc) ............................................................................................. 0.030/0.076 mm (0.0012/0.0030 in.)

CH25, CH26, CH730-750 ............................................................................... 0.025/0.048 mm (0.0010/0.0019 in.)

Middle Compression Ring-to-Groove Side Clearance

CH18, CH20, CH22 (624 cc) ........................................................................... 0.040/0.080 mm (0.0016/0.0031 in.)

CH22/23 (674 cc) ............................................................................................. 0.030/0.076 mm (0.0012/0.0030 in.)

CH25, CH26, CH730-750 ............................................................................... 0.015/0.037 mm (0.0006/0.0015 in.)

Oil Control Ring-to-Groove Side Clearance

CH18, CH20, CH22 (624 cc) ........................................................................... 0.060/0.202 mm (0.0024/0.0080 in.)

CH22/23 (674 cc) ............................................................................................. 0.046/0.196 mm (0.0018/0.0077 in.)

CH25, CH26, CH730-750 ............................................................................... 0.026/0.176 mm (0.0010/0.0070 in.)

1.12

Section 1

Safety and General Information

Piston, Piston Rings, and Piston Pin cont.

Top and Center Compression Ring End Gap

New Bore - CH18, CH20, CH22 (624 cc) ...................................................... 0.25/0.45 mm (0.0098/0.0177 in.)

New Bore - CH22/23 (674 cc) ........................................................................ 0.18/0.46 mm (0.0071/0.0181 in.)

New Bore - CH25, CH26, CH730-745 .......................................................... 0.25/0.56 mm (0.0100/0.0224 in.)

Used Bore (Max.) - CH18, CH20, CH22 (624 cc) .......................................... 0.77 mm (0.030 in.)

Used Bore (Max.) - CH22/23 (674 cc) ............................................................ 0.80 mm (0.0315 in.)

Used Bore (Max.) - CH25, CH26, CH730-750 .............................................. 0.94 mm (0.037 in.)

Piston Thrust Face O.D.²

New - CH18, CH20, CH22 (624 cc) ............................................................... 76.967/76.985 mm (3.0302/3.0309 in.)

New - CH22/23 (674 cc) ................................................................................. 79.963/79.979 mm (3.1481/3.1488 in.)

New - CH25, CH26, CH730-750 ................................................................... 82.986 mm (3.2671 in.)

Max. Wear Limit - CH18, CH20, CH22 (624 cc) .......................................... 76.840 mm (3.0252 in.)

Max. Wear Limit - CH22 (674 cc) ................................................................. 79.831 mm (3.1430 in.)

Max. Wear Limit - CH25, CH26, CH730-750 .............................................. 82.841 mm (3.2614 in.)

Piston Thrust Face-to-Cylinder Bore² Running Clearance

New - CH18, CH20, CH22 (624 cc) ............................................................... 0.014/0.057 mm (0.0005/0.0022 in.)

New - CH22/23 (674 cc) ................................................................................. 0.021/0.062 mm (0.0008/0.0024 in.)

New - CH25, CH26, CH730-750 ................................................................... 0.001/0.045 mm (0.039/0.0018 in.)

Speed Control Bracket

Fastener Torque ....................................................................................................... 10.7 N·m (95 in. lb.) into new holes

7.3 N·m (65 in. lb.) into used holes

Starter Assembly

Thru Bolt Torque

UTE/Johnson Electric, Eaton (Inertia Drive) ............................................... 4.5-5.7 N·m (40-50 in. lb.)

Nippondenso (Solenoid Shift) ...................................................................... 4.5-7.5 N·m (40-84 in. lb.)

Delco-Remy (Solenoid Shift) ......................................................................... 5.6-9.0 N·m (49-79 in. lb.)

Mounting Screw Torque (All) ............................................................................... 15.3 N·m (135 in. lb.)

Brush Holder Mounting Screw Torque

Delco-Remy Starter ........................................................................................ 2.5-3.3 N·m (22-29 in. lb.)

Solenoid (Starter)

Mounting Hardware Torque

Nippondenso Starter ..................................................................................... 6.0-9.0 N·m (53-79 in. lb.)

Delco-Remy Starter ........................................................................................ 4.0-6.0 N·m (35-53 in. lb.)

Nut, Positive (+) Brush Lead Torque

Nippondenso Starter ..................................................................................... 8.0-12.0 N·m (71-106 in. lb.)

Delco-Remy Starter ........................................................................................ 8.0-11.0 N·m (71-97 in. lb.)

Stator

Mounting Screw Torque ........................................................................................ 6.2 N·m (55 in. lb.)

²Measure 6 mm (0.236 in.) above the bottom of the piston skirt at right angles to the piston pin.

1.13

Section 1 Safety and General Information

Valve Cover

Valve Cover Fastener Torque

Gasket Style Cover ................................................................................................. 3.4 N·m (30 in. lb.)

Black O-Ring Style Cover

w/Shoulder Screws ........................................................................................ 5.6 N·m (50 in. lb.)

w/Flange Screws and Spacers ...................................................................... 9.9 N·m (88 in. lb.)

Yellow or Brown O-Ring Style Cover w/Integral Metal Spacers .................... 6.2 N·m (55 in. lb.)

Valves and Valve Lifters

Hydraulic Valve Lifter to Crankcase Running Clearance ................................ 0.0241/0.0501 mm (0.0009/0.0020 in.)

Intake Valve Stem-to-Valve Guide Running Clearance ................................... 0.038/0.076 mm (0.0015/0.0030 in.)

Exhaust Valve Stem-to-Valve Guide Running Clearance ................................ 0.050/0.088 mm (0.0020/0.0035 in.)

Intake Valve Guide I.D.

New .................................................................................................................. 7.038/7.058 mm (0.2771/0.2779 in.)

Max. Wear Limit............................................................................................. 7.134 mm (0.2809 in.)

Exhaust Valve Guide I.D.

New .................................................................................................................. 7.038/7.058 mm (0.2771/0.2779 in.)

Max. Wear Limit............................................................................................. 7.159 mm (0.2819 in.)

Valve Guide Reamer Size

Standard .......................................................................................................... 7.048 mm (0.2775 in.)

0.25 mm O.S. .................................................................................................... 7.298 mm (0.2873 in.)

Intake Valve Minimum Lift ................................................................................... 8.07 mm (0.3177 in.)

Exhaust Valve Minimum Lift ............................................................................... 8.07 mm (0.3177 in.)

Nominal Valve Seat Angle .................................................................................... 45°

1.14

General Torque Values

Section 1

Safety and General Information

Metric Fastener T orque Recommendations for St andard Applications

Tightening Torque: N·m (in. lb.) + or - 10%

Property Class

4.8

Size M4 1.2 (11) 1.7 (15) 2.9 (26) 4.1 (36) 5.0 (44) 2.0 (18) M5 2.5 (22) 3.2 (28) 5.8 (51) 8.1 (72) 9.7 (86) 4.0 (35) M6 4.3 (38) 5.7 (50) 9.9 (88) 14.0 (124) 16.5 (146) 6.8 (60) M8 10.5 (93) 13.6 (120) 24.4 (216) 33.9 (300) 40.7 (360) 17.0 (150)

5.8

8.8 10.9 12.9

Noncritical

Fasteners

Into Aluminum

Tightening Torque: N·m (ft. lb.) + or - 10%

Property Class

4.8

M10 21.7 (16) 27.1 (20) 47.5 (35) 66.4 (49) 81.4 (60) 33.9 (25) M12 36.6 (27) 47.5 (35) 82.7 (61) 116.6 (86) 139.7 (103) 61.0 (45) M14 58.3 (43) 76.4 (55) 131.5 (97) 184.4 (136) 219.7 (162) 94.9 (70)

5.8

8.8

10.9

12.9

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Fasteners

Into Aluminum

1.15

Section 1 Safety and General Information

English Fastener T orque Recommendations for St andard Applications

Tightening Torque: N·m (in. lb.) + or - 20%

Bolts, Screws, Nuts and Fasteners Assembled Into Cast Iron or Steel

Grade 2 Grade 5 Grade 8

Size 8-32 2.3 (20) 2.8 (25) --------- 2.3 (20) 10-24 3.6 (32) 4.5 (40) --------- 3.6 (32) 10-32 3.6 (32) 4.5 (40) --------- --------- 1/4-20 7.9 (70) 13.0 (115) 18.7 (165) 7.9 (70) 1/4-28 9.6 (85) 15.8 (140) 22.6 (200) --------- 5/16-18 17.0 (150) 28.3 (250) 39.6 (350) 17.0 (150) 5/16-24 18.7 (165) 30.5 (270) --------- --------- 3/8-16 29.4 (260) --------- --------- --------- 3/8-24 33.9 (300) --------- --------- ---------

Grade 2 or 5 Fasteners Into Aluminum

Tightening Torque: N·m (ft. lb.) + or - 20%

Size 5/16-24 --------- ---------- 40.7 (30) --------3/8-16 --------- 47.5 (35) 67.8 (50) --------3/8-24 --------- 54.2 (40) 81.4 (60) --------7/16-14 47.5 (35) 74.6 (55) 108.5 (80) --------7/16-20 61.0 (45) 101.7 (75) 142.4 (105) --------1/2-13 67.8 (50) 108.5 (80) 155.9 (115) --------1/2-20 94.9 (70) 142.4 (105) 223.7 (165) --------9/16-12 101.7 (75) 169.5 (125) 237.3 (175) --------9/16-18 135.6 (100) 223.7 (165) 311.9 (230) --------5/8-11 149.2 (110) 244.1 (180) 352.6 (260) --------5/8-18 189.8 (140) 311.9 (230) 447.5 (330) --------3/4-10 199.3 (150) 332.2 (245) 474.6 (350) --------3/4-16 271.2 (200) 440.7 (325) 637.3 (470) ---------

Torque

Conversions

N·m = in. lb. x 0.113 N·m = ft. lb. x 1.356 in. lb. = N·m x 8.85 ft. lb. = N·m x 0.737

1.16

Section 2

Tools & Aids

Certain quality tools are designed to help you perform specific disassembly, repair, and reassembly procedures. By using tools designed for the job, you can properly service engines easier, faster, and safer! In addition, you’ll increase your service capabilities and customer satisfaction by decreasing engine downtime.

Here is the list of tools and their source.

Separate Tool Suppliers:

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Tools & Aids

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2.3

Section 2 Tools & Aids

Special Tools You Can Make

Flywheel Holding Tool

A flywheel holding tool can be made out of an old junk flywheel ring gear as shown in Figure 2-1, and used in place of a strap wrench.

1. Using an abrasive cut-off wheel, cut out a six tooth segment of the ring gear as shown.

2. Grind off any burrs or sharp edges.

3. Invert the segment and place it between the ignition bosses on the crankcase so that the tool teeth engage the flywheel ring gear teeth. The bosses will lock the tool and flywheel in position for loosening, tightening or removing with a puller.

2. Remove the studs of a Posi-Lock rod or grind off the aligning steps of a Command rod, so the joint surface is flat.

3. Find a 1 in. long capscrew with the correct thread size to match the threads in the connecting rod.

4. Use a flat washer with the correct I.D. to slip on the capscrew and approximately 1” O.D. (Kohler Part No. 12 468 05-S). Assemble the capscrew and washer to the joint surface of the rod, as shown in Figure 2-2.

Figure 2-1. Flywheel Holding Tool.

Rocker Arm/Crankshaft Tool

A spanner wrench to lift the rocker arms or turn the crankshaft may be made out of an old junk connecting rod.

1. Find a used connecting rod from a 10 HP or larger engine. Remove and discard the rod cap.

Figure 2-2. Rocker Arm/Crankshaf t T ool.

2.4

Section 3

Troubleshooting

Troubleshooting Guide

When troubles occur, be sure to check the simple causes which, at first, may seem too obvious to be considered. For example, a starting problem could be caused by an empty fuel tank.

Some general common causes of engine troubles are listed below. Use these to locate the causing factors. Refer to the specific section(s) within this service manual for more detailed information.

Engine Cranks But Will Not Start

1. Empty fuel tank.

2. Fuel shut-off valve closed.

3. Poor fuel, dirt or water in the fuel system.

4. Clogged fuel line.

5. Spark plug lead(s) disconnected.

6. Key switch or kill switch in “off” position.

7. Faulty spark plugs.

8. Faulty ignition module(s).

9. SMART-SPARK

10. Carburetor solenoid malfunction.

11. Diode in wiring harness failed in open circuit mode.

12. Vacuum fuel pump malfunction, or oil in vacuum hose.

13. Vacuum hose to fuel pump leaking/cracked.

14. Battery connected backwards.

15. Safety interlock system engaged.

Engine Starts But Does Not Keep Running

1. Restricted fuel tank cap vent.

2. Poor fuel, dirt or water in the fuel system.

3. Faulty or misadjusted choke or throttle controls.

4. Loose wires or connections that short the kill terminal of ignition module to ground.

5. Faulty cylinder head gasket.

6. Faulty carburetor.

7. Vacuum fuel pump malfunction, or oil in vacuum hose.

8. Leaking/cracked vacuum hose to fuel pump.

9. Intake system leak.

malfunction (applicable models).

™

Section 3

Troubleshooting

10. Diode in wiring harness failed in open circuit mode.

Engine Starts Hard

1. PTO drive is engaged.

2. Dirt or water in the fuel system.

3. Clogged fuel line.

4. Loose or faulty wires or connections.

5. Faulty or misadjusted choke or throttle controls.

6. Faulty spark plugs.

7. Low compression.

8. Weak spark.

9. Fuel pump malfunction causing lack of fuel.

10. Engine overheated-cooling/air circulation restricted.

11. Quality of fuel.

12. Flywheel key sheared.

13. Intake system leak.

Engine Will Not Crank

1. PTO drive is engaged.

2. Battery is discharged.

3. Safety interlock switch is engaged.

4. Loose or faulty wires or connections.

5. Faulty key switch or ignition switch.

6. Faulty electric starter or solenoid.

7. Seized internal engine components.

Engine Runs But Misses

1. Dirt or water in the fuel system.

2. Spark plug lead disconnected.

3. Poor quality of fuel.

4. Faulty spark plug(s).

5. Loose wires or connections that intermittently ground the ignition kill circuit.

6. Engine overheated.

7. Faulty ignition module or incorrect air gap.

8. Carburetor adjusted incorrectly.

9. SMART-SPARK models).

malfunction (applicable

™

3.1

Section 3 Troubleshooting

Engine Will Not Idle

1. Dirt or water in the fuel system.

2. Stale fuel and/or gum in carburetor.

3. Faulty spark plugs.

4. Fuel supply inadequate.

5. Idle speed adjusting screw improperly set.

6. Idle fuel adjusting needle improperly set (some models).

7. Low compression.

8. Restricted fuel tank cap vent.

9. Engine overheated-cooling system/air circulation problem.

Engine Overheats

1. Air intake/grass screen, cooling fins, or cooling shrouds clogged.

2. Excessive engine load.

3. Low crankcase oil level.

4. High crankcase oil level.

5. Faulty carburetor.

6. Lean fuel mixture.

7. SMART-SPARK™ malfunction (applicable models).

Engine Knocks

1. Excessive engine load.

2. Low crankcase oil level.

3. Old or improper fuel.

4. Internal wear or damage.

5. Hydraulic lifter malfunction.

6. Quality of fuel.

7. Incorrect grade of oil.

Engine Loses Power

1. Low crankcase oil level.

2. High crankcase oil level.

3. Dirty air cleaner element.

4. Dirt or water in the fuel system.

5. Excessive engine load.

6. Engine overheated.

7. Faulty spark plugs.

8. Low compression.

9. Exhaust restriction.

10. SMART-SPARK models).

11. Low battery.

12. Incorrect governor setting.

malfunction (applicable

™

Engine Uses Excessive Amount of Oil

1. Incorrect oil viscosity/type.

2. Clogged or improperly assembled breather.

3. Breather reed broken.

4. Worn or broken piston rings.

5. Worn cylinder bore.

6. Worn valve stems/valve guides.

7. Crankcase overfilled.

8. Blown head gasket/overheated.

Oil Leaks from Oil Seals, Gaskets

1. Crankcase breather is clogged or inoperative.

2. Breather reed broken.

3. Loose or improperly torqued fasteners.

4. Piston blowby or leaky valves.

5. Restricted exhaust.

External Engine Inspection

Before cleaning or disassembling the engine, make a thorough inspection of its external appearance and condition. This inspection can give clues to what might be found inside the engine (and the cause) when it is disassembled.

• Check for buildup of dirt and debris on the crankcase, cooling fins, grass screen, and other external surfaces. Dirt or debris on these areas are causes of higher operating temperatures and overheating.

• Check for obvious fuel and oil leaks, and damaged components. Excessive oil leakage can indicate a clogged or improperly-assembled breather, worn/damaged seals and gaskets, or loose or improperly-torqued fasteners.

• Check the air cleaner cover and base for damage or indications of improper fit and seal.

• Check the air cleaner element. Look for holes, tears, cracked or damaged sealing surfaces, or other damage that could allow unfiltered air into the engine. Also note if the element is dirty or clogged. These could indicate that the engine has been under serviced.

• Check the carburetor throat for dirt. Dirt in the throat is further indication that the air cleaner is not functioning properly.

3.2

• Check the oil level. Note if the oil level is within the operating range on the dipstick, or if it is low or overfilled.

Section 3

Troubleshooting

• Check the condition of the oil. Drain the oil into a container - the oil should flow freely. Check for metal chips and other foreign particles.

Sludge is a natural by-product of combustion; a small accumulation is normal. Excessive sludge formation could indicate overrich carburetion, weak ignition, overextended oil change interval or wrong weight or type of oil was used, to name a few.

NOTE: It is good practice to drain oil at a

location away from the workbench. Be sure to allow ample time for complete drainage.

Cleaning the Engine

After inspecting the external condition of the engine, clean the engine thoroughly before disassembling it. Also clean individual components as the engine is disassembled. Only clean parts can be accurately inspected and gauged for wear or damage. There are many commercially available cleaners that will quickly remove grease, oil, and grime from engine parts. When such a cleaner is used, follow the manufacturer’s instructions and safety precautions carefully.

Make sure all traces of the cleaner are removed before the engine is reassembled and placed into operation. Even small amounts of these cleaners can quickly break down the lubricating properties of engine oil.

Basic Engine Tests

Crankcase Vacuum Test

A partial vacuum should be present in the crankcase when the engine is operating. Pressure in the crankcase (normally caused by a clogged or improperly assembled breather) can cause oil to be forced out at oil seals, gaskets, or other available spots.

To test the crankcase vacuum with the manometer:

1. Insert the stopper/hose into the oil fill hole. Leave the other tube of manometer open to atmosphere. Make sure the shut off clamp is closed.

2. Start the engine and run at no-load high speed (3200 to 3750 RPM).

3. Open the clamp and note the water level in the tube.

The level in the engine side should be a minimum of 10.2 cm (4 in.) above the level in the open side.

If the level in the engine side is less than specified (low/no vacuum), or the level in the engine side is lower than the level in the open side (pressure), check for the conditions in the table on page 3.4.

4. Close the shut off clamp before stopping the engine.

To test the crankcase vacuum with the Vacuum/ Pressure Gauge Kit (see Section 2):

1. Remove the dipstick or oil fill plug/cap.

2. Install the adapter into the oil fill/dipstick tube opening, upside down over the end of a small diameter dipstick tube, or directly into engine if a tube is not used.

3. Push the barbed fitting on the gauge solidly into the hole in the adapter.

4. Start the engine and bring it up to operating speed (3200-3600 RPM).

Crankcase vacuum is best measured with either a water manometer or a vacuum gauge (see Section 2). Complete instructions are provided in the kits.

5. Check the reading on the gauge. If the reading is to the left of “0” on the gauge, vacuum or negative pressure is indicated. If the reading is to the right of “0” on the gauge, positive pressure is present.

Crankcase vacuum should be 4-10 (inches of water) If the reading is below specification, or if pressure is present, check the following table for possible causes and remedies.

3.3

Section 3 Troubleshooting

No Crankcase Vacuum/Pressure in Crankcase

Possible Cause

1. Crankcase breather clogged or inoperative.

2. Seals and/or gaskets leaking. Loose or improperly torqued fasteners.

3. Piston blowby or leaky valves (confirm by inspecting components).

4. Restricted exhaust.

Compression T est

Some of these engines are equipped with an automatic compression release (ACR) mechanism. Because of the ACR mechanism, it is difficult to obtain an accurate compression reading. As an alternative, perform a cylinder leakdown test.

Cylinder Leakdown T est

A cylinder leakdown test can be a valuable alternative to a compression test. By pressurizing the combustion chamber from an external air source you can determine if the valves or rings are leaking, and how badly.

Cylinder Leakdown Tester (see Section 2) is a relatively simple, inexpensive leakdown tester for small engines. The tester includes a quick disconnect for attaching the adapter hose, and a holding tool.

Leakdown T est Instructions

1. Run engine for 3-5 minutes to warm it up.

2. Remove spark plug(s) and air filter from engine.

3. Rotate the crankshaft until the piston (of cylinder being tested) is at top dead center of the compression stroke. Hold the engine in this position while testing. The holding tool supplied with the tester can be used if the PTO end of the crankshaft is accessible. Lock the holding tool onto the crankshaft. Install a 3/8" breaker bar into the hole/slot of the holding tool, so it is perpendicular to both the holding tool and crankshaft PTO.

Solution

1. Disassemble breather, clean parts thoroughly, check sealing surfaces for flatness, reassemble, and recheck pressure.

2. Replace all worn or damaged seals and gaskets. Make sure all fasteners are tightened securely. Use appropriate torque values and sequences when necessary.

3. Recondition piston, rings, cylinder bore, valves, and valve guides.

4. Repair/replace restricted muffler/exhaust system.

If the flywheel end is more accessible, use a breaker bar and socket on the flywheel nut/ screw to hold it in position. An assistant may be needed to hold the breaker bar during testing. If the engine is mounted in a piece of equipment, it may be possible to hold it by clamping or wedging a driven component. Just be certain that the engine cannot rotate off of TDC in either direction.

4. Install the adapter into the spark plug hole, but do not attach it to the tester at this time.

5. Connect an air source of at least 50 psi to the tester.

6. Turn the regulator knob in the increase (clockwise) direction until the gauge needle is in the yellow “set” area at the low end of the scale.

7. Connect the tester quick-disconnect to the adapter hose while firmly holding the engine at TDC. Note the gauge reading and listen for escaping air at the carburetor intake, exhaust outlet, and crankcase breather.

8. Check your test results against the following table:

3.4

Section 3

Troubleshooting

Leakdown Test Results

Air escaping from crankcase breather ........................................................ Defective rings or worn cylinder.

Air escaping from exhaust system .............................................................. Defective exhaust valve/improper seating.

Air escaping from carburetor....................................................................... Defective intake valve/improper seating.

Gauge reading in “low” (green) zone .......................................................... Piston rings and cylinder in good

condition.

Gauge reading in “moderate” (yellow) zone .............................................. Engine is still usable, but there is some

wear present. Customer should start planning for overhaul or replacement.

Gauge reading in “high” (red) zone ............................................................. Rings and/or cylinder have considerable

wear. Engine should be reconditioned or replaced.

3.5

Air Cleaner and Air Intake System

Air Cleaners

Section 4

General

Most engines are equipped with a replaceable, highdensity paper air cleaner element, surrounded by an oiled foam precleaner, and housed under a flat outer cover. This is typically referred to as the standard air cleaner assembly. See Figures 4-1 and 4-4. Some engines utilize a heavy-duty style air cleaner as shown in Figure 4-12.

Figure 4-1. Standard Air Cleaner.

Figure 4-2. Removing Latch Style Cover.

Cover

Air Cleaner Element

Precleaner

Standard Air Cleaner

Service

Check the air cleaner daily or before starting the engine. Check for and correct any buildup of dirt and

debris, along with loose or damaged components.

NOTE: Operating the engine with loose or damaged

air cleaner components could allow unfiltered air into the engine, causing premature wear and failure.

Figure 4-3. Removing Knob Style Cover .

Precleaner Service

If so equipped, wash and reoil the precleaner every 25 hours of operation (more often under extremely dusty

or dirty conditions).

To service the precleaner, perform the following steps:

1. Unhook the latches or loosen the retaining knob, and remove the cover.

2. Remove the foam precleaner from the paper air cleaner element.

4.1

Section 4 Air Cleaner and Air Intake System

3. Wash the precleaner in warm water with detergent. Rinse the precleaner thoroughly until all traces of detergent are eliminated. Squeeze out excess water (do not wring). Allow the precleaner to air dry.

4. Saturate the precleaner with new engine oil. Squeeze out all excess oil.

5. Reinstall the precleaner over the paper air cleaner element.

6. Reinstall the air cleaner cover. Secure the cover with the two latches or the retaining knob.

Element Cover

Element

Figure 4-4. Air Cleaner Components.

Wing Nut

Precleaner

Seal

Figure 4-6. Removing Elements.

Figure 4-7. Removing Rubber Seal from Bracket.

Paper Element Service (Standard Type)

Every 100 hours of operation (more often under extremely dusty or dirty conditions), replace the paper element. Follow these steps:

Figure 4-5. Removing Element Cover Wing Nut.

4.2

1. Unhook the latches or loosen the retaining knob, and remove the cover.

2. Remove the wing nut, element cover, and paper element with precleaner (if so equipped).

3. Remove the precleaner (if so equipped) from the paper element. Service the precleaner as described in "Precleaner Service".

4. Do not wash the paper element or use pressurized air, as this will damage the element. Replace a dirty, bent, or damaged element with a genuine Kohler element. Handle new elements carefully; do not use if the sealing surfaces are bent or damaged.

Section 4

Air Cleaner and Air Intake System

5. Check the seal for any damage or deterioration. Replace as necessary. See Figure 4-7.

6. Reinstall the seal, paper element, precleaner, element cover, and wing nut.

7. Reinstall the air cleaner cover and secure with the latches or the retaining knob.

NOTE: Make sure the correct depth air cleaner

element and rubber seal are used for the engine spec involved. Some engines use a deeper or extra capacity air cleaner and a longer rubber seal.

Figure 4-8. Exploded View of St andard Air Int ake System Component s.

4.3

Section 4 Air Cleaner and Air Intake System

Figure 4-9. Bracket Retaining Screw.

Air Cleaner Element Cover and Seal - Make sure element cover is not bent or damaged. Make sure the wing nut and seal are in place to ensure the element is sealed against leakage.

Air Cleaner Base - Make sure the base is secured tightly to the carburetor and not cracked or damaged.

Breather Tube - Make sure the tube is attached to both the air cleaner base and the breather cover.

NOTE: Damaged, worn or loose air cleaner

components can allow unfiltered air into the engine causing premature wear and failure. Tighten or replace all loose or damaged components.

Rear Mounting Screws

Figure 4-10. Rear Mounting Screws (Used with Plastic Intake Manifold).

Complete Disassembly and Reassembly Standard Type

If the base plate on the standard type has to be removed, proceed as follows:

1. Remove air cleaner components as described earlier.

2. Remove the hex flange screws securing the bracket and base. See Figures 4-9 and 4-10. Remove the bracket.

3. Pinch the sealing collar on the breather hose and push it down through the hole in the air cleaner base. Carefully feed the upper section of the breather tube down through the base. See Figure 4-11.

4. Remove the base and gasket.

5. Reverse the procedure to reinstall new or serviced components. Torque screws to 9.9 N·m (88 in. lb.).

Heavy-Duty Air Cleaner

Figure 4-11. Breather Tube.

Air Cleaner Components

Whenever the air cleaner cover is removed, or the paper element or precleaner are serviced, check the following:

4.4

General

The heavy-duty air cleaner consists of a cylindrical housing, typically mounted to a bracket off the upper valve cover screws, and connected with a formed rubber hose to an adapter on the carburetor or throttle body/intake manifold (EFI units). The air cleaner housing contains a paper element and inner element, designed for longer service intervals. The system is CARB/EPA certified and the components should not be altered or modified in any way.

Figure 4-12. Heavy-Duty Air Cleaner .

To Service

Every 250 hours of operation (more often under extremely dusty or dirty conditions), replace the paper element and check the inner element. Follow these steps.

1. Unhook the two retaining clips and remove the end cap from the air cleaner housing.

Section 4

Air Cleaner and Air Intake System

4. Do not wash the paper element and inner

element or use compressed air, this will damage the elements. Replace dirty, bent or damaged elements with new genuine Kohler elements as required. Handle the new elements carefully; do not use if the sealing surfaces are bent or damaged.

5. Check all parts for wear, cracks, or damage. Replace any damaged components.

6. Install the new inner element, followed by the outer element. Slide each fully into place in the air cleaner housing.

7. Reinstall the end cap so the dust ejector valve is down, and secure with the two retaining clips. See Figure 4-12.

Removal

1. Remove the upper valve cover screws on each side, securing the main bracket, and loosen the hose clamp on the adapter inlet, or remove the adapter mounting screws.

2. Pull the air cleaner element out of the housing. See Figure 4-13.

Inner

Element

Figure 4-13. Removing Elements.

3. After the element is removed, check the condition of the inner element. It should be replaced whenever it appears dirty, typically every other time the main element is replaced. Clean the area around the base of the inner element before removing it, so dirt does not get into the engine.

Element

2. Lift the entire air cleaner assembly off the engine. Disassemble or service as required.

Installation

1. Install the main mounting bracket with the center section up and the cutout around the carburetor, aligning the mounting holes with the four upper valve cover holes.

2. Install and torque the four valve cover mounting screws to specified torque value.

3. Reconnect the hose to the adapter and tighten the clamp, or install a new adapter gasket (if the adapter was separated from the carburetor), and torque the mounting fasteners to 7.3 N·m (65 in. lb.).

NOTE: Adapter configurations may vary

depending on engine and application involved. Two adapters are shown in Figure 4-14.

4.5

Section 4 Air Cleaner and Air Intake System

Figure 4-14. Adapters for Heavy-Duty Air Cleaners.

Air Intake/Cooling System

To ensure proper cooling, make sure the grass screen, cooling fan fins, and external surfaces of the engine are kept clean at all times.

Every 100 hours of operation (more often under extremely dusty or dirty conditions), remove the blower housing and other cooling shrouds. *Clean the cooling fins and external surfaces as necessary. Make sure the cooling shrouds are reinstalled.

*Cleanout kits, Kohler Part No. 25 755 20-S (black) or

25 755 21-S (gold), are recommended to aid inspection and cleanout of the cooling fins. See Figure 4-15.

NOTE: Operating the engine with a blocked grass

screen, dirty or plugged cooling fins, and/or cooling shrouds removed, will cause engine damage due to overheating.

Figure 4-15. Cleanout Kit Installed on Blower Housing.

4.6

Fuel System and Governor

Section 5

Fuel System and Governor

Section 5

Description

The Command horizontal twins use three different types of fuel systems; carbureted, electronic fuel injection (EFI), or gaseous. Gaseous fuel systems can be either liquefied petroleum gas (LPG or LP) or natural gas (NG). Some dual-fuel engines have a combination system, which allows the operator to select either gasoline or LP.

This section covers the standard carbureted fuel systems. The gaseous systems are covered in subsection 5A and the EFI systems are covered in subsection 5B. The governor systems used are covered at the end of this section.

WARNING: Explosive Fuel!

Fuel System Components

The typical carbureted fuel system and related components include the following:

Fuel then enters the carburetor float bowl and is drawn into the carburetor body. There, the fuel is mixed with air. This fuel-air mixture is then burned in the engine combustion chamber.

Fuel Recommendations

General Recommendations

• Do not use gasoline left over from the previous season, to minimize gum deposits in your fuel system and to ensure easy starting.

• Do not add oil to the gasoline.

• Do not overfill the fuel tank. Leave room for the fuel to expand.

Fuel T y pe

For best results, use only clean, fresh, unleaded gasoline with a pump sticker octane rating of 87 or higher. In countries using the Research fuel rating method, it should be 90 octane minimum.

• Fuel Tank

• Fuel Lines

• In-line Fuel Filter

• Fuel Pump

• Carburetor

Operation

The fuel from the tank is moved through the in-line filter and fuel lines by the fuel pump. On engines not equipped with a fuel pump, the fuel tank outlet is located above the carburetor inlet allowing gravity to feed fuel to the carburetor.

Gasoline/Alcohol blends

Gasohol (up to 10% ethyl alcohol, 90% unleaded gasoline by volume) is approved as a fuel for Kohler engines. Other gasoline/alcohol blends are not approved.

5.1

Section 5 Fuel System and Governor

Gasoline/Ether blends

Methyl Tertiary Butyl Ether (MTBE) and unleaded gasoline blends (up to a maximum of 15% MTBE by volume) are approved as a fuel for Kohler engines. Other gasoline/ether blends are not approved.

Fuel Filter

Most engines are equipped with an in-line fuel filter. Periodically inspect the filter and replace with a genuine Kohler filter every 200 operating hours.

Fuel Line

In compliance with CARB Tier III Emission Regulations, carbureted engines with a “Family” identification number beginning with “6” or greater (See Figure 5-1), must use Low Permeation SAE 30 R7 rated fuel line; certified to meet CARB requirements. Standard fuel line may not be used. Order replacement hose by part number through a Kohler Engine Service Dealer.

IMPORTANT ENGINE INFORMATION THIS ENGINE MEETS U.S. EPA AND CA 2005 AND LATER AND EC STAGE II (SN:4) EMISSION REGS FOR SI SMALL OFF–ROAD ENGINES

FAMILY 6 KHXS.7252 PH TYPE APP

DISPL. (CC) MODEL NO.

N11236

SPEC. NO. SERIAL NO. BUILD DA TE OEM PROD. NO.

EMISSION COMPLIANCE PERIOD: EPA: CARB: CERTIFIED ON: REFER TO OWNER'S MANUAL FOR HP RATING, SAFETY, MAINTENANCE AND ADJUSTMENTS

1-800-544-2444 www.kohlerengines.com

KOHLER CO. KOHLER, WISCONSIN USA

Figure 5-1. “Family” Number Location.

5.2

Section 5

Fuel System and Governor

Fuel System T ests

When the engine starts hard, or turns over but will not start, it is possible that the problem is in the fuel system. To find out if the fuel system is causing the problem, perform the following tests.

Troubleshooting – Fuel System Related Causes

T est Conclusion

1. Check the following: a. Make sure the fuel tank contains clean, fresh,

proper fuel.

b. Make sure the vent in fuel tank is open.

c. Make sure the fuel valve is open.

d. Make sure vacuum and fuel lines to fuel

pump are secured and in good condition.

2. Check for fuel in the combustion chamber. a. Disconnect and ground spark plug leads.

b. Close the choke on the carburetor.

c. Crank the engine several times.

d. Remove the spark plug and check for fuel at

the tip.

3. Check for fuel flow from the tank to the fuel

pump.

a. Remove the fuel line from the inlet fitting of

fuel pump.

b. Hold the line below the bottom of the tank.

Open the shut-off valve (if so equipped) and observe flow.

4. Check the operation of fuel pump. a. Remove the fuel line from the inlet fitting of

carburetor.

b. Crank the engine several times and observe

flow.

2. If there is fuel at the tip of the spark plug, fuel is

reaching the combustion chamber.

If there is no fuel at the tip of the spark plug, check for fuel flow from the fuel tank (Test 3).

3. If fuel does flow from the line, check for faulty

fuel pump (Test 4).

If fuel does not flow from the line, check the fuel tank vent, fuel pickup screen, in-line filter, shutoff valve, and fuel line. Correct any observed problem and reconnect the line.

4. If fuel does flow from the line, check for faulty

carburetor. (Refer to the "Carburetor" portions of this section.)

If fuel does not flow from the line, check for a clogged fuel line. If the fuel line is unobstructed, check for overfilled crankcase and/or oil in pulse line. If none of the checks reveal the cause of the problem, replace the pump.

5.3

Section 5 Fuel System and Governor

Fuel Pump

General

These engines are equipped with either a pulse or mechanical fuel pump. See Figures 5-2 and 5-3. The pumping action is created by either the oscillation of positive and negative pressures within the crankcase through a hose, or by direct lever/pump actuation off rocker arm movement. The pumping action causes the diaphragm on the inside of the pump to pull fuel in on its downward stroke and to push it into the carburetor on its upward stroke. Internal check valves prevent fuel from going backward through the pump.

Outlet Line (to Carburetor)

Pulse Fuel Pump

Pulse Line

Inlet Line

NOTE: On most models, the pulse line is

connected to a fitting on the crankcase, while on early models, it is connected to the valve cover.

4. Install the new fuel pump using the hex flange

screws. Torque the hex flange screws to 2.3 N·m (20 in. lb.).

NOTE: Make sure the orientation of the new

pump is consistent with the removed pump. Internal damage may occur if installed incorrectly.

5. Connect the pulse line to the pulse fitting.

6. Connect the fuel lines to the inlet and outlet fittings.

Replacing the Mechanical Pump

The mechanical pump is an integral part of the valve cover assembly and not serviced separately. See Figure 5-3.

1. Disconnect the fuel lines from the inlet and outlet fittings.

Figure 5-2. Pulse Style Fuel Pump.

Performance

Minimum fuel delivery rate must be 7.5 L/hr. (2 gal./hr.) with a pressure at 0.3 psi and a fuel lift of 18 in. from carburetor inlet. A 1.3 L/hr. (0.34 gal./hr.) fuel rate must be maintained at 5 Hz.

Fuel Pump - Replacement

Replacing the Pulse Fuel Pump

Replacement pumps are available through your source of supply. To replace the pulse pump follow these steps:

1. Disconnect the fuel lines from the inlet and outlet fittings.

2. Remove the hex flange screws securing the fuel pump.

3. Remove the pulse line that connects the pump to the crankcase or valve cover.

2. Follow the procedure for replacing the valve cover (Sections 9 and 11).

3. Reconnect the fuel lines to the inlet and outlet fittings.

Outlet Line (to Carburetor)

Mechanical Fuel Pump

Inlet Line

Figure 5-3. Mechanical Fuel Pump.

5.4

Section 5

Fuel System and Governor

Carburetor

General

Engines in this series are equipped with Keihin fixed main jet carburetors. CH18-740 engines use a onebarrel carburetor. Most applications use a fuel shutoff solenoid installed in place of the fuel bowl retaining screw, and also contain an accelerator pump. All carburetors feature a self-relieving choke like or similar to the one shown in the exploded view on page 5.10. CH750 engines use a Keihin BK twobarrel carburetor on a matching intake manifold. This carburetor with related servicing and adjustments is covered beginning on page 5.11.

Troubleshooting - Carburetor Related Causes

Condition

1. Engine starts hard, runs roughly or stalls at idle speed.

2. Engine runs rich (indicated by black, sooty exhaust smoke, misfiring, loss of speed and power, governor hunting, or excessive throttle opening).

1. Low idle fuel mixture (some models)/speed improperly adjusted. Adjust the low idle speed tab, then adjust the low idle fuel needle.

2a. Clogged air cleaner. Clean or replace.

b. Choke partially closed during operation. Check the choke lever/

linkage to ensure choke is operating properly.

c. Low idle fuel mixture is improperly adjusted. Adjust low idle

fuel needle (some models).

d. Float level is set too high. Separate carburetor air horn from

carburetor body, adjust float to specification.

e. Dirt under the fuel inlet needle. Remove needle; clean needle and

seat and blow with compressed air.

f. Bowl vent or air bleeds plugged. Remove low idle fuel adjusting

needle. Clean vent, ports, and air bleeds. Blow out all passages with compressed air.

g. Leaky, cracked or damaged float. Submerge float to check for

leaks.

WARNING: Explosive Fuel

Possible Cause/Probable Remedy

3. Engine runs lean (indicated by misfiring, loss of speed and power, governor hunting or excessive throttle opening).

4. Fuel leaks from carburetor. 4a. Float level set too high. See Remedy 2d.

3a. Low idle fuel mixture is improperly adjusted. Adjust low idle

fuel needle (some models).

b. Float level is set too low. Separate carburetor air horn from

carburetor body, adjust float specification.

c. Idle holes plugged; dirt in fuel delivery channels. Remove low

idle fuel adjusting needle. Clean main fuel jet and all passages; blow out with compressed air.

b. Dirt under fuel inlet needle. See Remedy 2e.

c. Bowl vents plugged. Blow out with compressed air.

d. Carburetor bowl gasket leaks. Replace gasket.

5.5

Section 5 Fuel System and Governor

Troubleshooting Checklist

When the engine starts hard, runs roughly or stalls at low idle speed, check the following areas before adjusting or disassembling the carburetor.

• Make sure the fuel tank is filled with clean, fresh gasoline.

• Make sure the fuel tank cap vent is not blocked and that it is operating properly.

• Make sure fuel is reaching the carburetor. This includes checking the fuel shut-off valve, fuel tank filter screen, in-line fuel filter, fuel lines and fuel pump for restrictions or faulty components as necessary.

• Make sure the air cleaner base and carburetor are securely fastened to the engine using gaskets in good condition.

• Make sure the air cleaner element (including precleaner if equipped) is clean and all air cleaner components are fastened securely.

When current is removed the pin extends blocking the main fuel jet and preventing fuel from entering the carburetor.

One-Barrel Carburetor

Fuel Shut-off Solenoid

T wo-Barrel Carburetor

• Make sure the ignition system, governor system, exhaust system, and throttle and choke controls are operating properly.

If the engine is hard-starting, runs roughly, or stalls at low idle speed, it may be necessary to adjust or service the carburetor.

High Altitude Operation

When operating the engine at altitudes of 1500 m (5000 ft.) and above, the fuel mixture tends to get overrich. This can cause conditions such as black, sooty exhaust smoke, misfiring, loss of speed and power, poor fuel economy, and poor or slow governor response.

To compensate for the effects of high altitude, special high altitude jet kits are available. The kits include a new main jet, slow jet (where applicable), necessary gaskets and O-Rings. Refer to the parts manual for the correct kit number.

Fuel Shut-off Solenoid

Most carburetors are equipped with a fuel shut-off solenoid. The solenoid is attached in place of the fixed main jet screw on the flywheel side of the carburetor. See Figure 5-4. The solenoid has a spring-loaded pin that retracts when 12 volts is applied to the lead, allowing fuel flow through the main jet.

Fuel Shut-off Solenoid

Figure 5-4. Fuel Shut-off Solenoid.

Below is a simple test, made with the engine off, that can determine if the solenoid is functioning properly:

1. Shut off fuel and remove the solenoid from the carburetor. When the solenoid is loosened and removed, gas will leak out of the carburetor. Have a container ready to catch the fuel.

2. Wipe the tip of the solenoid with a shop towel or blow it off with compressed air, to remove any remaining fuel. Take the solenoid to a location with good ventilation and no fuel vapors present. You will also need a 12 volt power source that can be switched on and off.

3. Be sure the power source is switched “off”. Connect the positive power source lead to the red lead of the solenoid. Connect the negative power source lead to the solenoid bracket.

4. Turn the power source “on” and observe the pin in the center of the solenoid. The pin should retract with the power “on” and return to its original position with the power off. Test several times to verify operation.

5.6

Section 5

Fuel System and Governor

Carburetor Adjustments (CH18-740)

General

In compliance with government emission standards, the carburetor is calibrated to deliver the correct airto-fuel mixture to the engine under all operating conditions. The high-speed mixture is preset and cannot be adjusted. Pre-compliance carburetors contain a low idle fuel adjusting needle, on “certified” compliance carburetors, both the low and high speed mixture circuits are pre-established and cannot be adjusted. The low idle speed (RPM) is the only adjustment available. See Figures 5-5 and 5-6.

Depending on model and application, engines may also be equipped with a “Governed Idle System.” If equipped with a “Governed Idle System”, refer to “Models with Governed Idle System” when performing any carburetor adjustment, as an additional step to the listed adjustment procedure(s) is required.

Low Idle Speed Adjustment

Low Idle Fuel Adjusting Needle

NOTE: Carburetor adjustments should be made

only after the engine has warmed up.

Adjusting Low Idle Speed and Fuel (Some Models)

To adjust the carburetor idle speed, see Figure 5-5 and follow these steps.

1. With the engine stopped, turn the low idle fuel adjusting needle in clockwise until it bottoms lightly.

NOTE: The tip of the idle fuel adjusting needle

is tapered to critical dimensions. Damage to the needle and the seat in the carburetor body will result if the needle is forced.

2. Now turn the adjusting needle out counterclockwise 1-1/2 turns.

3. Start the engine and run at half throttle for 5 to 10 minutes to warm up. The engine must be warm before making final settings. Check that the throttle and choke plates can fully open.

Main Jet Location

Figure 5-5. Pre-Compliance Carburetor with Low Idle Adjustment.

Low Idle Speed Adjustment

Fuel Shut-Off Solenoid (Main Jet Location)

NOTE: The carburetor has a self-relieving

choke. Choke plate and shaft assembly is spring loaded. Check to make sure plate moves freely and is not binding and affecting idle fuel delivery.

4. Place the throttle control into the “idle” or “slow” position. Turn the low idle speed adjusting screw in or out to obtain a low idle speed of 1200 RPM (± 75 RPM). Check the speed using a tachometer.

NOTE: The actual low idle speed depends on

the application. Refer to the equipment manufacturer’s recommendations. The low idle speed for basic engines is 1200 RPM. To ensure best results when setting the low idle fuel needle, the low idle speed should be 1200 RPM (± 75 RPM).

5. Turn the low idle fuel adjusting needle in (slowly) until engine speed decreases and then back out approximately 3/4 turn to obtain the best low speed performance.

6. Recheck the idle speed using a tachometer and readjust the speed as necessary.

Figure 5-6. “Certified” Compliance Carburetor.

5.7

Section 5 Fuel System and Governor

Models with Governed Idle System

An optional governed idle control system is supplied on some engines. The purpose of this system is to maintain a desired idle speed regardless of ambient conditions (temperature, parasitic load, etc.) that may change. Engines with this feature contain a small secondary spring connected between the governor lever and the lower adjustment tab of the main bracket. See Figure 5-7.

The system requires an additional procedure for setting the idle speed. If speed adjustments are required proceed as follows.

Hold Throttle Lever Against Screw

1. Make any necessary speed or control adjustments following the appropriate instructions covered in this section.

2. Move the throttle control to the idle position. Hold the governor lever away from the carburetor, or hold the throttle lever so it is tight against the idle speed adjusting screw, to negate the governor activation. See Figure 5-8. Check the speed with a tachometer and adjust it to 1500 RPM.

3. Release the governor lever and allow the engine to return to the governed idle speed. Check it with a tachometer against the equipment manufacturers recommended idle speed. Governed Idle Speed (RPM) is typically 300 RPM (approximate) higher than the low idle speed. If adjustment is necessary, bend the adjusting tab on the speed control assembly to set. See Figure 5-7.

Figure 5-8. Holding Throttle Lever Against Idle Stop Screw (One-Barrel Carburetor).

Servicing

Float

It is not necessary to remove the carburetor from the engine to check and adjust the float.

1. Remove the air cleaner and breather hose. Refer to Section 9 – ‘‘Disassembly”.

2. Disconnect the fuel line from the carburetor. See Figure 5-9.

3. Clean dirt and debris from exterior of carburetor.

4. Remove the four screws holding the two carburetor halves together. Carefully lift the upper body off the carburetor body and disconnect choke linkage.

Governed Idle Spring

Figure 5-7. Governed Idle Spring Location.

5.8

Screws

Fuel Line

Tab

Figure 5-9. Carburetor Detail.

5. Hold the carburetor upper body so that the float assembly hangs vertically and rests lightly against the fuel inlet needle. The fuel inlet needle should be fully seated, but the needle tip should not be depressed. See Figure 5-10.

Section 5

Fuel System and Governor

NOTE: The fuel inlet needle tip is spring loaded.

Make sure the float assembly rests against the fuel inlet needle without depressing the tip.

6. The correct float height adjustment is 22 mm (0.86 in.), measured from the float bottom to the air horn casting. Adjust the float height by carefully bending the tab.

NOTE: Be sure to measure from the casting

surface, not the rubber gasket surface.

7. If proper float height adjustment cannot be achieved, check to see if the fuel inlet needle is dirty, obstructed or worn. Remove the brass screw and float assembly to remove the fuel inlet needle.

Tab

2. Remove the four screws and carefully separate the air horn assembly from the carburetor body.

3. Loosen the screw securing the float assembly to the air horn and remove the float, float shaft and fuel inlet needle.

4. Remove the slow jet from the carburetor body.

NOTE: The main jet is a fixed jet and can be

removed if required. Fixed jets for high altitude are available.

5. Remove the black cap on the end of the choke shaft only if it is necessary to inspect and clean the shaft spring.

6. Remove the low idle speed adjusting screw and spring from the carburetor body.

7. In order to clean the ‘‘off-idle’’ vent ports and bowl vent thoroughly, use a good carburetor solvent (like Gumout air through the idle adjusting needle hole. Be careful to use a suitable shop rag to prevent debris from hitting someone.

™

). Blow clean compressed

Float

Figure 5-10. Carburetor Float Adjustment.

8. Once the proper float height is obtained, carefully lower the carburetor air horn assembly onto the carburetor body, connecting the choke linkage. Install the four screws. Torque the screws to 1.7 N·m (15 in. lb.). See Figure 5-9.

9. Connect the fuel line.

10. Install the breather hose and air cleaner assembly, following the steps in Section 11 – ‘‘Reassembly”.

Disassembly

Disassemble the carburetor using the following steps. See Figure 5-11.

1. Remove the air cleaner, breather hose and carburetor. Refer to Section 9 – “Disassembly”.

8. Remove the preformed rubber gasket only if it is to be replaced. If it is removed for any reason, replace it.

Inspection/Repair

Carefully inspect all components and replace those that are worn or damaged.

• Inspect the carburetor body for cracks, holes and other wear or damage.

• Inspect the float for cracks, holes, and missing or damaged float tabs. Check the float hinge and shaft for wear or damage.

• Inspect the fuel inlet needle and seat for wear or damage.

• Inspect the tip of the low idle fuel adjusting needle for wear or grooves.

• The choke plate is spring loaded. Check to make sure it moves freely on the shaft.

5.9

Section 5 Fuel System and Governor

NOTE: The choke and throttle plate assemblies

are staked and matched to the shafts at the factory. They are not serviceable items.

Always use new gaskets when servicing or reinstalling carburetors. Repair kits are available which include new gaskets and other components. These kits are described on the next page.

Reassembly

Reassemble the carburetor using the following steps. See Figure 5-11.

1. Assemble the fuel inlet needle to the float tab. Install the float, float shaft and inlet needle to the

5 6

air horn. Tighten the screw. Check float height using the procedure found previously in the ‘‘Adjustments’’ subsection.

2. Install the slow jet with the stepped end toward the bottom of the carburetor. Make sure jet is fully seated.

3. Install the low idle adjusting needle and spring.

4. Assemble the upper body onto the lower carburetor body using the four screws. Torque the screws to 1.7 N·m (15 in. lb.).

5. Install the carburetor on the engine following the procedures in Section 11 – ‘‘Reassembly.’’

1. Carburetor Upper Body (Choke)

2. Self-relieving Choke

3. Body Gasket (Formed Rubber)

4. Slow Speed Jet

5. Inlet Needle Valve

6. Clip

7. Float Pin

8. Float Assembly (Kit)

9. Carburetor Lower Body (Throttle)

10. Main Jet

11. Idle Fuel Adjusting Needle (some models)

12. Solenoid Seat

13. Fuel Shut-off Solenoid (Kit)

14. Idle Speed Adjusting Screw

15. Jet (Accelerator Pump Carburetor only)

16. Accelerator Pump Cover

17. Diaphragm

18. Diaphragm Spring

19. O-Ring

20. Rubber Boot

21. Bushing

22. Return Spring

Figure 5-11. CH18-740 Carburetor – Exploded V iew .

5.10

See Note on Page 5.11

Accelerator Pump Version Only

Section 5

Fuel System and Governor

Components such as the throttle and choke shaft assemblies, throttle plate, choke plate, low idle fuel needle, and others, are available separately.

Always refer to the Parts Manual for the engine being serviced, to ensure the correct repair kits and replacement parts are ordered. Service/repair kits available for the carburetor and affiliated components are:

Carburetor Repair Kit Float Kit High Altitude Kit (1525-3048 m/5,000-10,000 ft.) High Altitude Kit (over 3048 m/10,000 ft.) Solenoid Assembly Kit Accelerator Pump Seal and Bushing Kit Accelerator Pump Diaphragm Kit Choke Repair Kit

NOTE: If accelerator pump rod movement is

restricted or corrosion exists in the pump rod housing hole; use a 0.153 in. (3.9 mm) or No. 23 drill and carefully clean (resize) the hole to restore proper operation. Blow out the hole with air and lightly lubricate with oil on reassembly.

Carburetor

Keihin BK T wo-Barrel Carburetor (CH750)

The carburetor used on CH750 engines is a Keihin two-barrel side draft design with fixed main jets. See Figure 5-12. A self-relieving choke similar to that used on single venturi carburetors is also contained in the design. The circuits within the carburetor function as described following:

Slow & Mid-Range Circuit:

At low speeds the engine operates only on the slow circuit. As a metered amount of air is drawn through the slow air bleed jets, fuel is drawn through the two main jets and further metered through the slow jets. Air and fuel are mixed in the body of the slow jet and exit to the transfer port. From the transfer port the air fuel mixture is delivered to the idle progression chamber. From the idle progression chamber the air fuel mixture is metered through the idle port passages. At low idle when the vacuum signal is weak, the air/fuel mixture is controlled by the setting of the idle fuel adjusting screws. This mixture is then mixed with the main body of air and delivered to the engine. As the throttle plate opening increases, greater amounts of air/fuel mixture are drawn in through the fixed and metered idle progression holes. As the throttle plate opens further the vacuum signal becomes great enough so the main circuit begins to work.

Main (High-Speed) Circuit:

At high speeds/loads the engine operates on the main circuit. As a metered amount of air is drawn through the four air jets, fuel is drawn through the main jets. The air and fuel are mixed in the main nozzles and then enter the main body of airflow, where further mixing of the fuel and air occurs. This mixture is then delivered to the combustion chamber. The carburetor has a fixed main circuit; no adjustment is possible.

Carburetor Adjustments

Adjustment

NOTE: Carburetor adjustments should be made

only after the engine has warmed up.

Float Circuit:

The fuel level in the bowl is maintained by the float and fuel inlet needle. The buoyant force of the float stops fuel flow when the engine is at rest. When fuel is being consumed, the float will drop and fuel pressure will push the inlet needle away from the seat, allowing more fuel to enter the bowl. When demand ceases, the buoyant force of the float will again overcome the fuel pressure, rising to the predetermined setting and stop the flow.

The carburetor is designed to deliver the correct fuelto-air mixture to the engine under all operating conditions. The main fuel jet is calibrated at the factory and is not adjustable*. The idle fuel adjusting needle is also set at the factory and normally does not need adjustment.

5.11

Section 5 Fuel System and Governor

*NOTE: Engines operating at altitudes above

approximately 1500 m (5000 ft.) may require a special ‘‘high altitude’’ main jet. Refer to ‘‘High Altitude Operation.’’

If, however, the engine is hard-starting or does not operate properly, it may be necessary to adjust or service the carburetor.

Low Idle Fuel Adjustments (With Limiters)

Low Idle Speed (RPM) Adjustment Screw

Fuel Solenoid

Figure 5-12. Keihin T wo-Barrel Carburetor.

2. Place the throttle control into the “idle” or “slow” position. Adjust the low idle speed to 1200 RPM*. Follow the “Adjusting the Low Idle Speed (RPM)” procedure.

3. Low Idle Fuel Needle(s) Setting: Place the throttle into the “idle” or “slow” position.

a. Turn one of the low idle fuel adjusting needles

out (counterclockwise) from the preliminary setting until the engine speed decreases (rich). Note the position of the needle. Now turn the adjusting needle in (clockwise). The engine speed may increase, then it will decrease as the needle is turned in (lean). Note the position of the needle. Set the adjusting needle midway between the rich and lean settings. See Figure 5-13.

b. Repeat the procedure on the other low idle

adjustment needle.

4. Recheck/adjust the Low Idle Speed (RPM), to the specified setting.

Carburetor Adjustment

Low Idle Speed (RPM) Adjustment

1. Low Idle Speed (RPM) Setting: Place the throttle control into the “idle” or “slow” position. Set the low idle speed to 1200 RPM* (± 75 RPM) by turning the low idle speed adjusting screw in or out. Check the speed using a tachometer.

*NOTE: The actual low idle speed depends on the

application. Refer to the equipment manufacturer’s recommendations. The low idle speed for basic engines is 1200 RPM. To ensure best results when setting the low idle fuel needle, the low idle speed should be 1200 RPM (± 75 RPM).

Low Idle Fuel Adjustment

NOTE: Engines will have fixed low idle or limiter

caps on the two idle fuel adjusting needles. Step 3 can only be performed within the limits allowed by the cap. Do not attempt to remove the limiter caps.

1. Start the engine and run at half throttle for 5 to 10 minutes to warm up. The engine must be warm before doing steps 2, 3, and 4.

Adjust to

Lean

Midpoint

Rich

Left Side Right Side

Figure 5-13. Optimum Low Idle Fuel Settings.

Adjust to Midpoint

Rich

Lean

Models with Governed Idle System

The system requires an additional procedure for setting the idle speed. If speed adjustments are required proceed as follows.

5.12

Section 5

Fuel System and Governor

1. Make any necessary speed or control adjustments following the appropriate instructions covered in this section.

2. Move the throttle control to the idle position. Hold the governor lever away from the carburetor, or hold the throttle lever so it is tight against the idle speed adjusting screw, to negate the governor activation. See Figure 5-15. Check the speed with a tachometer and adjust it to 1500 RPM.

Carburetor Servicing

Float Replacement

If symptoms described in the carburetor troubleshooting guide indicate float level problems, remove the carburetor from the engine to check and/ or replace the float. Use a float kit to replace the float, pin, float valve, clip and screw.

1. Perform the removal procedures for the Heavy Duty Air Cleaner and Carburetor outlined in Section 9 “Disassembly.”

2. Clean the exterior surfaces of dirt or foreign material before disassembling the carburetor. Remove the four mounting screws and carefully separate the fuel bowl from the carburetor. Do not damage the inner or bowl O-Ring. Transfer any remaining fuel into an approved container. Save all parts. Fuel can also be drained prior to bowl removal by loosening/removal of the bowl drain screw. See Figure 5-16.

Governed Idle Spring

Tab

Figure 5-14. Governed Idle Spring Location.

Hold Throttle Lever Against Screw

Fuel Bowl

Bowl Drain Screw

Figure 5-16. Fuel Bowl Removed From Carburetor.

Figure 5-15. Holding Throttle Lever Against Idle Stop Screw (Two-Barrel Carburetor).

5.13

Section 5 Fuel System and Governor

3. Remove the float pin screw and lift out the old float, pin and inlet needle. See Figure 5-17. Discard all of the parts. The seat for the inlet needle is not serviceable, and should not be removed.

Figure 5-17. Removing Float and Inlet Needle.

4. Clean the carburetor bowl and inlet seat areas as required, before installing the new parts.

5. Attach the inlet needle to the plastic tang of the float with the wire clip. The formed 90° lip should point up, with the needle valve hanging down. See Figure 5-18.

Figure 5-19. Installing Float Assembly.

7. Hold the carburetor body so the float assembly hangs vertically and rests lightly against the fuel inlet needle. The inlet needle should be fully seated but the center pin of the needle (on retainer clip end) should not be depressed. Check the float height adjustment.

NOTE: The inlet needle center pin is spring loaded.

Make sure the float rests against the fuel inlet needle without depressing the center pin.

8. The correct float height setting is 17 mm (0.669 in.) ± 1.5 mm (0.059 in.), measured from the float bottom to the body of the carburetor. See Figure 5-20. Replace the float if the height is different than the specified setting. DO NOT attempt to adjust by bending float tab.

Figure 5-18. Float and Inlet Needle Details.

6. Install the float and inlet needle down into the seat and carburetor body. Install the new pivot pin through the float hinge and secure with the new retaining screw. See Figure 5-19.

5.14

Figure 5-20. Checking Float Height.

NOTE: Be sure to measure from the casting surface,

not the rubber gasket, if still attached.

Section 5

Fuel System and Governor

9. When the proper float height is obtained, carefully reinstall the fuel bowl, using new O-Rings onto the carburetor. Secure with the four original screws. Torque the screws to

2.5 ± 0.3 N·m (23 ± 2.6 in. lb.). See Figure 5-21.

Figure 5-21. Installing Fuel Bowl.

10. Install the carburetor and the heavy-duty air cleaner as outlined in Section 11 “Reassembly.”

Disassembly/Overhaul

1. Clean the exterior surfaces of dirt or foreign material before disassembling the carburetor. Remove the four mounting screws and separate the fuel bowl from the carburetor. Transfer any remaining fuel into an approved container. Remove and discard the old O-Rings. Fuel can also be drained prior to bowl removal by loosening/removal of the bowl drain screw. See Figure 5-22.

Fuel Bowl

NOTE: Further disassembly of the fuel bowl is not

necessary unless the Fuel Solenoid Kit, or Fuel Bowl Kit (obtained separately), will also be installed.

2. Remove the float pin screw and lift out the old float, pin, and inlet needle. See Figure 5-23. Discard all the old parts. The seat for the inlet needle is not serviceable, and should not be removed.

Figure 5-23. Removing Float and Inlet Needle.

3. Use an appropriate size flat screwdriver, and carefully remove the two main jets from the carburetor. Note and mark the jets by location for proper reassembly. The main jets may be size/side specific. After the main jets are removed, the main nozzles can be removed out through the bottom of the main towers. Note the orientation/direction of the nozzles. The end with the two raised shoulders should be out/down adjacent to the main jets. Save the parts for cleaning and reuse. See Figure 5-24.

Bowl Drain Screw

Figure 5-22. Fuel Bowl Removed From Carburetor.

Main Nozzles

Main Jets

Figure 5-24. Main Jets and Nozzles Removed.

5.15

Section 5 Fuel System and Governor

4. Remove the screw securing the flat washer and ground lead (if equipped), from the top of the carburetor; then carefully pull (lift) out the two slow jets. The slow jets may be sized/side specific, mark or tag for proper reassembly. Note the small O-Ring on the bottom of each jet. See Figures 5-25 and 5-26. Save parts for cleaning and reuse unless a Jet Kit is also being installed. Clean the slow jets using compressed air. Do not use wire or carburetor cleaner.

6. Clean the carburetor body, main jets, vent ports, seats, etc. using a good commercially available carburetor solvent. Keep away from plastic or rubber parts if non-compatible. Use clean, dry compressed air to blow out the internal channels and ports. Do not use metal tools or wire to clean orifices and jets. Inspect and thoroughly check the carburetor for cracks, wear, or damage. Inspect the fuel inlet seat for wear or damage. Check the spring loaded choke plate to make sure it moves freely on the shaft.

7. Clean the carburetor fuel bowl as required.

8. Install the two main nozzles into the towers of the carburetor body. The end of the main nozzles with the two raised shoulders should be out/ down (adjacent to the main jets). Make sure the nozzles are completely bottomed. Carefully install the main jets into the towers of the carburetor body on the appropriate side, as identified when removal was performed. See Figure 5-27.

Figure 5-25. Removing Screw and Washer.

Slow (Idle Fuel) Jets

O-Ring

Figure 5-26. Slow Jets and O-Ring Detail.

5. Remove the idle speed (RPM) adjustment screw and spring from the carburetor. Discard the parts.

NOTE: The carburetor is now disassembled for

appropriate cleaning and installation of the parts in the overhaul kit. Further disassembly is not necessary. The throttle shaft assembly, fuel inlet seat, idle fuel adjustment screws with limiter, and carburetor body, are nonserviceable items and should not be removed. The choke shaft assembly is serviceable, however it should not be removed unless a Choke Repair Kit will be installed.

Nozzle End with T wo Shoulders (Out/Down)

Figure 5-27. Installing Main Nozzles and Main Jets.

9. Make sure the O-Ring near the bottom of each slow jet is new, or in good condition. Align and insert the two slow jets into the top of carburetor. See Figure 5-26.

10. Install the large flat retaining washer and secure with the mounting screw, attaching the ground lead if originally secured by the screw.

11. Install the new idle speed (RPM) adjustment screw and spring onto the carburetor. Thread in until 3 or 4 threads are exposed, as an initial adjustment. See Figure 5-28.

Main Jets

5.16

Section 5

Fuel System and Governor

Figure 5-28. Installing Idle Speed Adjusting Screw and Spring.

12. Attach the inlet needle to the plastic tang of the float with the wire clip. The formed 90° lip should point up, with the needle valve hanging down. See Figure 5-29.

Figure 5-29. Float and Inlet Needle Details.

13. Install the float and inlet needle down into the seat and carburetor body. Install the new pivot pin through the float hinge and secure with the new retaining screw. See Figure 5-30.

Figure 5-30. Installing Float Assembly.

14. Hold the carburetor body so the float assembly hangs vertically and rests lightly against the fuel inlet needle. The inlet needle should be fully seated but the center pin of the needle (on retainer clip end) should not be depressed. Check the float height adjustment.

NOTE: The inlet needle center pin is spring loaded.

Make sure the float rests against the fuel inlet needle without depressing the center pin.

15. The correct float height setting is 17 mm (0.669 in.) ± 1.5 mm (0.059 in.), measured from the float bottom to the body of the carburetor. See Figure 5-31. Replace the float if the height is different than the specified setting. Do not attempt to adjust by bending float tab.

Figure 5-31. Checking Float Height.

NOTE: Be sure to measure from the casting surface,

not the rubber gasket, if still attached.

5.17

Section 5 Fuel System and Governor

16. When the proper float height is obtained, carefully reinstall the fuel bowl, using new O-Rings onto the carburetor. Secure with the four original screws. Torque the screws to

2.5 ± 0.3 N·m (23 ± 2.6 in. lb.). See Figure 5-32.

Figure 5-32. Installing Fuel Bowl.

Choke Repair

1. Remove the carburetor from the engine. Discard the old mounting gaskets for the air cleaner and carburetor.

5. Use a screw extractor (easy-out) and remove the original choke shaft bushing with the old choke lever from the carburetor housing. Save the bushing to use as a driver for installing the new bushing. Discard the old lever.

6. Clean the I.D. of both choke shaft bores as required.

7. Insert the new bushing through the new choke lever from the outside, and start the bushing in the outer shaft bore. Position the choke lever so the protruding boss on the carburetor housing is between the two stops formed in the choke lever. See Figure 5-34.

Stops

Boss

2. Clean the areas around the choke shaft and the self-relieving choke mechanism thoroughly.

3. Remove and discard the plastic cap from the end of the choke lever/shaft assembly.

4. Note the position of the spring legs and the choke plate for correct reassembly later. See Figure 5-33. Remove the two screws attaching the choke plate to the choke shaft. Pull the shaft out of the carburetor body and discard the removed parts.

Figure 5-34. Assembling Choke Lever .

8. Turn the old bushing upside down and use it as a driver to carefully press or tap the new bushing into the carburetor body until it bottoms. Check that the choke lever pivots freely without restriction or binding. See Figure 5-35.

Figure 5-33. Choke Details.

5.18

Figure 5-35. Installing Bushing.

9. Install the new return spring onto the new choke shaft, so the upper leg of the spring is between the two formed “stops” on the end of the choke shaft. See Figure 5-36.

NOTE: Make sure it stays in this location during the

following step.

Figure 5-36. Choke Shaft and Spring Details.

10. Slide the choke shaft and spring into the carburetor. Pivot (preload) the shaft and set the inner leg of the spring, against the formed stop within the choke lever as originally assembled. See Figure 5-33. The opposing leg of the spring must still be between the formed “stops” of the choke shaft.

11. Place a drop of Loctite® on the threads of each new screw. Position and install the new choke plate to the flat side of the choke shaft. Start the two screws. Close the choke and check the plate alignment within the carburetor throat, then tighten the screws securely. Do not overtighten. See Figure 5-37.

Section 5

Fuel System and Governor

Figure 5-37. Installing Choke Plate.

12. Check for proper operation and free movement of the parts. Install the new cap.

Always use new gaskets when servicing or reinstalling carburetors. Repair kits are available which include new gaskets and other components. Service/repair kits available for Keihin BK two-barrel carburetors and affiliated components are:

Carburetor Overhaul Kit Float Kit Fuel Solenoid Kit Choke Repair Kit Bowl Kit High Altitude Kit (1525-3048 m/5,000-10,000 ft.) High Altitude Kit (Over 3048 m/10,000 ft.)

5.19

Section 5 Fuel System and Governor

4 5 6

21 20

1. Carburetor Body Subassembly

2. Idle Speed Screw

3. Idle Speed Spring

4. Screw

5. Ground Lead

6. Retaining Washer

7. Slow Jet - RH Side

8. Slow Jet - LH Side

9. O-Ring (Slow Jet) (2)

10. Fuel Bowl

11. O-Ring (Fuel Bowl - Upper)

12. O-Ring (Fuel Bowl - Lower)

13. Drain Screw

14. Bowl Screw (4)

15. Fuel Solenoid

16. Sealing Washer

17. Float

18. Pin

19. Screw

20. Float Clip

21. Float Valve/Inlet Needle

22. Main Nozzle - Right Side

23. Main Nozzle - Left Side

24. Main Jet - Right Side

25. Main Jet - Left Side

26. Choke Dust Cap

27. Choke Shaft

28. Spring

29. Bushing

30. Choke Lever

31. Choke Plate

32. Choke Plate Screw (2)

Figure 5-38. Keihin BK Two-Barrel Carburetor - Exploded View.

5.20

Section 5

Fuel System and Governor

Governor

General

The governor is designed to hold the engine speed constant under changing load conditions. Most engines are equipped with a centrifugal flyweight mechanical governor. Some engines utilize an optional electronic governor, which is shown and covered on page 5.23. The governor gear/flyweight mechanism of the mechanical governor is mounted inside the crankcase and is driven off the gear on the camshaft. This governor design works as follows:

• Centrifugal force acting on the rotating governor gear assembly causes the flyweights to move outward as speed increases. Governor spring tension moves them inward as speed decreases.

Governor Spring

Cross Shaft

Governor Arm

Hex Nut

Throttle Linkage

Figure 5-39. Governor Linkage.

• As the flyweights move outward, they cause the regulating pin to move outward.

• When load is applied and the engine speed and governor gear speed decreases, the governor spring tension moves the governor arm to open the throttle plate wider. This allows more fuel into the engine, increasing the engine speed. As the speed reaches the governed setting, the governor spring tension and the force applied by the regulating pin will again offset each other to hold a steady engine speed.

Adjustments

NOTE: Do not tamper with the governor setting.

Overspeed is hazardous and could cause personal injury.

General

The governed speed setting is determined by the position of the throttle control. It can be variable or constant, depending on the engine application.

Initial Adjustment

NOTE: EFI engines require a special initial

adjustment procedure, which is covered in subsection 5B. Refer to “Initial Governor Adjustment” in that section for setting the governor on EFI-equipped engines.

Procedure – Carburetor Equipped Engines

Make this adjustment whenever the governor arm is loosened or removed from the cross shaft. See Figure 5-39 and adjust as follows:

1. Make sure the throttle linkage is connected to the governor arm and the throttle lever on the carburetor.

• The regulating pin contacts the tab on the cross shaft causing the shaft to rotate.

• One end of the cross shaft protrudes through the crankcase. The rotating action of the cross shaft is transmitted to the throttle lever of the carburetor through the external throttle linkage. See Figure 5-39.

• When the engine is at rest, and the throttle is in the “fast” position, the tension of the governor spring holds the throttle plate open. When the engine is operating, the governor gear assembly is rotating. The force applied by the regulating pin against the cross shaft tends to close the throttle plate. The governor spring tension and the force applied by the regulating pin balance each other during operation, to maintain engine speed.

2. Loosen the hex nut holding the governor lever to the cross shaft.

3. Move the governor lever toward the carburetor as far as it will move (wide open throttle) and hold in this position.

4. Insert a nail into the hole on the cross shaft and rotate the shaft counterclockwise as far as it will turn, then tighten hex nut securely.

5.21

Section 5 Fuel System and Governor

Sensitivity Adjustment

Governor sensitivity is adjusted by repositioning the governor spring in the holes of the governor lever. If speed surging occurs with a change in engine load, the governor is set too sensitive. If a big drop in speed occurs when normal load is applied, the governor should be set for greater sensitivity. See Figure 5-40 and adjust as follows:

1. To increase the sensitivity, move the spring closer to the governor cross shaft.

2. To decrease the sensitivity, move the spring away from the governor cross shaft.

High Speed (RPM) Adjustment (Refer to Figure 5-41.)

1. With the engine running, move the throttle control to fast. Use a tachometer to check the RPM speed.

2. Loosen the lock nut on high speed adjusting screw. Turn the screw outward to decrease, or inward to increase the RPM speed. Check RPM with a tachometer.

3. When the desired RPM speed is obtained, retighten the lock nut.

NOTE: When the throttle and choke control cables

are routed side-by-side, especially under a single clamp, there must be a small gap between the cables to prevent internal binding. After the high-speed setting has been completed, check that there is a gap of at least 0.5 mm (0.020 in.) between the control cables.

Governor Lever

Figure 5-40. Governor Sensitivity Adjustments.

Left Side Pull

Choke Control Lever #1

Choke Control Cable

Throttle Control Cable

Kill Switch Adjusting Screw

Dual Control High Speed Lever Stop Screw "Do Not Remove"

Figure 5-41. Governor Control Connections.

Kill Switch

High Speed Adjusting Screw

High Speed Control Lever

Throttle Control Lever #2

Choke Linkage

Z Bend

Throttle Control Cable

Choke Control Cable

Right Side Pull

5.22

Section 5

Fuel System and Governor

Electronic Governor

General

The electronic governor regulates engine speed at varying loads. It consists of a governor control unit, digital linear actuator and linkage.

Figure 5-42. Electronic Governor Assembly .

1. Digital Linear Actuator

2. Throttle Linkage

3. Linkage Spring

4. Choke Linkage

5. Throttle Lever Adapter

Governor Control Unit (GCU) senses engine speed by pulse voltage inputs from the ignition modules. The GCU regulates the engine speed by variable input voltage from a customer-supplied potentiometer or a single pole, single throw (SPST) switch.

Potentiometer Specifications:

Wiper Voltage

0-1 1-9 9-16

SPST Switch Specifications:

Switch Position

Open Closed

GCU Safety Features

In the event of an engine overspeed condition, the GCU will shut down the engine by grounding the ignition modules.

The GCU will shut down the engine by grounding the ignition when power to the GCU is lost.

Linkage

The throttle linkage spring will fully open the throttle plate if the linkage becomes detached from the DLA. This will create an overspeed condition causing the engine to shut down. The DLA shaft will have to be manually screwed back into the body, and then retracted before reassembling the linkage.

Engine Speed (RPM)

1860 low speed endpoint variable speed endpoint 3600 high speed endpoint

Engine Speed (RPM)

1860 low speed endpoint 3600 high speed endpoint

Governor Control Unit

Figure 5-43. Electronic Governor Assembly .

Digital Linear Actuator (DLA)

Energizing the bi-directional digital linear actuator coils in the proper sequence, causes the threaded shaft to move out of, or back into the rotor, in precise linear increments. When power is removed, the actuator shaft remains in position. The DLA must initialize (fully extend) to move the throttle plate to the closed position, and partially open for starting. Correct adjustment of the DLA is critical to achieve the full range of throttle plate movement. See Adjustment Procedure.

Adjustment Procedure

The DLA must be in the fully retracted position during assembly. The full range of throttle plate movement will not be achieved if the DLA is partially extended when assembled. Loosen the two DLA mounting plate screws located on the top of the actuator plate. With the throttle linkage centered in the U-Clip at the end of the DLA shaft, slide the DLA bracket assembly back until the throttle plate is fully open. Torque the mounting plate screws to 2.5 N·m (22 in. lb.).

5.23

Section 5 Fuel System and Governor

Troubleshooting Procedure

Engine starts, but will not continue to run

1. Check the linkage connection between the DLA and throttle plate.

2. Verify the DLA initializes when power is supplied (key switch in the start or run position).

3. Test the potentiometer wiper output voltage (if equipped).

4. Test the SPST switch (if equipped).

5. Check the wire harness and connections.

Engine does not run at the expected speed

1. Check to see that the throttle linkage and DLA have full range of motion having no mechanical interference.

2. Test the potentiometer wiper voltage (if equipped).

3. Test the SPST switch (if equipped).

5.24

Section 5A

LPG Fuel Systems

Section 5A

LPG Fuel Systems

WARNING: Explosive Fuel!

LPG is extremely flammable, is heavier than air, and tends to settle in low areas where a spark or flame could ignite the gas. Do not start or operate this engine in a poorly ventilated area where leaking gas could accumulate and endanger the safety of persons in the area.

Proper service and repair of LPG fuel systems requires qualified technicians and special equipment. Many states require special licensing or certification for LPG repair shops and/or technicians. Check state and local regulations before attempting any adjustment, service, or repair of the LPG system or components. Faulty repairs by unqualified or underqualified personnel can have very serious ramifications. The information in this segment is for the exclusive use of qualified LPG service providers.

LPG Fuel System Components

The typical “liquid withdrawal” LPG fuel system consists of the following components:

• LPG Fuel Tank (Liquid Withdrawal)

• Electric Lock-Off/Filter Assembly

• Vaporizer

• LPG Regulator (Combination Primary/Secondary/Vacuum Lock-Off)

• LPG Carburetor

• High Pressure Fuel Line(s)

• Vacuum Line

Fuel Line

Vaporizer

Vacuum Line

Figure 5A-1.

Lock-Off/Filter Assembly

LPG Regulator

5A.1

Section 5A LPG Fuel Systems

Operation

In a liquid withdrawal system, the Liquefied Petroleum Gas (LPG) is released from the bottom of the supply tank under high pressure. Upon opening the shut-off valve on the tank, liquid fuel travels out through the high pressure line to the electric lock-off/ filter assembly. The lock-off opens internally when the key switch is turned “on,” permitting filtered fuel to flow to the vaporizer. The vaporizer is mounted in the flow of the discharged cooling air. It absorbs heat from the cooling air and transfers it to the fuel, changing the liquefied petroleum to a vapor or gaseous state, while partially stepping down the fuel pressure. The gas/ vapor flows under this decreased pressure to the regulator where it is further reduced to a usable, regulated pressure. The regulator, activated by intake manifold vacuum, controls fuel flow to the carburetor. In the venturi of the carburetor, the fuel vapor is mixed with incoming air from the air cleaner in the correct ratio for efficient combustion.

Troubleshooting Checklist

If the engine starts hard, runs roughly, or stalls, check the following areas.

• Make sure the LPG fuel tank is filled and shut-off valve is fully opened.

• Make sure fuel is reaching the carburetor.

• Make sure the air cleaner element and precleaner are clean and all components are fastened securely.

• Make sure the ignition, governor, exhaust, throttle, and choke control systems are all operating properly.

• Check compression.

If engine continues to start hard, run roughly, or stall after these checks have been made, use the following troubleshooting guide.

Engine cranks but will not start

1. LPG fuel tank closed, low, or empty.

2. Lock-off not opening electrically, preventing fuel flow to vaporizer.

3. Fuel filter (located inside lock-off) dirty or blocked.

4. Insufficient vacuum signal, regulator not opening. a. Vacuum line between carburetor and

regulator cracked, leaking, kinked, or pinched. b. Carburetor loose. c. Intake manifold loose or leaking. d. Excessive internal engine wear.

5. Faulty regulator. a. Primary valve not opening. b. Diaphragm spring adjustment incorrect. c. Idle adjustment screw incorrectly set. d. Vent(s) blocked/restricted.

6. Restricted/blocked fuel line.

7. Blocked carburetor fuel circuit.

8. Loose/leaking fuel enrichment hose (Impco carburetor system).

Hard starting, runs roughly, or stalls at idle speed

1. LPG fuel tank low.

2. Vacuum line between carburetor and regulator pinched, cracked, or leaking.

3. Carburetor idle speed set too low (should be at least 1200 RPM).

4. Carburetor idle circuit restricted.

5. Dirty/restricted air cleaner.

6. Dirty/restricted lock-off filter.

7. Frozen/malfunctioning regulator. Check/adjust primary pressure.

8. Excessive external load on engine.

9. Excessive internal wear.

10. Loose/leaking fuel enrichment hose (Impco carburetor system).

Irregular or inconsistent idle

1. Improper operation/adjustment of regulator, idle adjustment screw, throttle opening, and/or engine governor.

2. Secondary valve in regulator not closing. Readjust idle screw (couterclockwise) so valve can close fully against seat.

3. Loose/leaking vacuum line.

4. Loose carburetor mounting and/or line connections.

5. Damaged diaphragm(s) within regulator.

6. Debris in regulator. Flush debris from drain plug or remove regulator from system, disassemble body and remove debris.

7. Dirt or debris in carburetor. Remove carburetor, disassemble and clean/service as required. If venturi (Impco carburetor) removal is performed, mark its orientation to the carburetor body for proper reinstallation.

8. Loose/leaking fuel enrichment hose (Impco carburetor system).

5A.2

Section 5A

LPG Fuel Systems

Engine stalls during operation

1. No fuel.

2. Faulty lock-off or blocked filter.

3. Improper governor setting.

4. Damaged diaphragms within regulator.

5. Vacuum line leaking, loose, or pinched.

6. Restricted fuel line.

7. Loose/leaking fuel enrichment hose (Impco carburetor system).

Low power

1. Air cleaner or exhaust system dirty/restricted.

2. Low fuel.

3. Rich gas condition (flooding) through regulator. a. Dirty/restricted valves in regulator. b. Damaged primary diaphragm in regulator.

4. No fuel. a. Electric lock-off not opening, filter blocked, or

restriction within fuel line.

b. Leaking, loose, or cracked vacuum line from

carburetor to regulator. c. Leaking, or loose intake system components. d. Regulator primary valve not opening. e. Secondary, or vacuum lock-off diaphragm

within regulator leaking. f. Low pressure rubber hose kinked. g. Frozen regulator.

5. Improper ignition timing.

6. Loose/incorrect throttle lever/clamp bracket positioning.

7. Loose or incorrectly positioned high speed throttle plate stop.

Engine runs lean

1. Electrical problem causing intermittent lock-off operation, or lock-off is faulty.

2. Filter in lock-off dirty or restricted.

3. Restriction in fuel system.

4. Idle holes plugged; dirt in fuel delivery channels.

5. Carburetor fuel circuit restriction.

6. Loose/leaking fuel enrichment hose (Impco carburetor system).

LPG Carburetor Adjustment s

General

The LPG carburetor and regulator are designed to deliver the correct fuel-to-air mixture to the engine under all operating conditions. The high and low idle fuel mixture settings are preset at the factory, and cannot be adjusted. These engines are equipped with an Impco or Nikki carburetor. See Figure 5A-2 and 5A-3. Although both carburetors function similarly, each is unique and should not be interchanged.

Load Block Assembly

Fuel Enrichment Hose

Venturi Retaining Screw

Fuel Inlet

Figure 5A-2. Impco Carburetor.

Choke Plate/Shaft Assembly

Rear Plug with Sealing Washer

Fuel Inlet

Plastic Bushing

Figure 5A-3. Nikki Carburetor.

Idle Speed Adjusting Screw

Transfer Chamber Cover

Vacuum Port

Idle Speed Adjusting Screw

High fuel consumption

1. Fuel leak. Check lines, connections, and system components for leaks with soapy water. Fix any leaks immediately.

2. Incorrectly set regulator, or leakage from valves in regulator. Readjust, service, or replace regulator as required.

3. Dirty air cleaner or precleaner.

4. Choke plate in carburetor not opening completely.

Impco carburetors also incorporate the use of an external ‘‘Load Block’’ assembly, which controls the final fuel flow to the carburetor for all throttle positions except idle. See Figure 5A-2. Calibrated and flow-matched to the carburetor, it functions similarly to preset fuel mixture settings in other carburetors. The load block assembly is not available separately, nor is any internal servicing permitted or possible. If a problem is encountered and determined to be caused by the load block, the carburetor should be replaced.

5A.3

Section 5A LPG Fuel Systems

High Altitude Operation

The standard carburetor calibrations will provide proper operation up to altitudes of 1500 m (5000 ft.). No internal changes are necessary or available for either carburetor.

NOTE: Carburetor adjustments should be made only

after the engine has warmed up.

Idle Speed Adjustment

1. Start the engine and run at half throttle for 5 to 10 minutes. Check that the throttle and choke (Nikki carburetor) plates can open fully.

2. Place the throttle control into the “idle” or “slow” position. Turn the low idle speed adjusting screw (See Figure 5A-2 or 5A-3) in or out, to obtain a low idle speed of 1200 RPM (± 75 RPM), or set to application specifications. Check the speed using a tachometer.

NOTE: The actual low idle speed (RPM) depends on

the application. Refer to the equipment manufacturer’s recommendations. The low idle speed for basic engines is 1200 RPM.

Impco Carburetor

1. Turn off fuel supply at tank.

2. Remove the air cleaner, breather hose, fuel line, vacuum hose, choke, and throttle linkages. Remove the mounting hardware, carburetor, and gaskets from the engine. Discard the gaskets.

3. The carburetor venturi may be removed for inspection and appropriate cleaning.

a. Remove the four screws securing the air

cleaner adapter and gasket to the carburetor. See Figure 5A-4.

LPG Fuel System Component Service

LPG Carburetor - Cleaning

The carburetor may be cleaned if necessary. Removal from the engine and limited disassembly will aid in cleaning.

NOTE: Impco Carburetor: Do not loosen or alter the

mounted position of the clamping brackets and/or stop collar on the throttle shaft. Each is preset, in correlation to a specific position of the throttle plate (shaft), or acts as a stop. None of these attached components, including the throttle plate or shaft, requires disassembly or removal for any carburetor servicing. All the components on the throttle shaft should be left intact. If the settings of any one of these is inadvertently loosened or altered, each must be checked/reset, or performance and operation will be affected. Refer to the procedure included in the reassembly/installation sequence to check or reset.

Figure 5A-4.

b. Important: Mark a small line on the outer

edge of the venturi for proper orientation and reinstallation later.

c. Loosen the venturi retaining screw on the side

of the carburetor body and lift out the venturi. See Figure 5A-5.

5A.4

Figure 5A-5.

Section 5A

LPG Fuel Systems

4. Inspect the overall condition of the fuel enrichment hose attached to the carburetor. It must be free of cracks, deterioration, and damage. Disconnect the fuel enrichment hose from the carburetor fittings to clean or check condition as required. See Figure 5A-6. Replace with a new Kohler high pressure hose (LP rated) if the condition is questionable in any way. Secure new hose using new clamps.

Figure 5A-6.

Nikki Carburetor

1. Turn off fuel supply at tank.

2. Remove the air cleaner, breather hose, fuel line, vacuum hose, choke, and throttle linkages. Remove the nuts, carburetor, and gaskets from the engine. Discard the gaskets.

3. Remove the fuel transfer chamber cover by removing the three screws. See Figure 5A-3. Carefully remove the cover and gasket. Discard the gasket.

4. The main jet is fixed and nonadjustable, but may be accessed for cleaning by removing the rear plug and sealing washer. Discard the washer.

5. In order to clean the off-idle transfer passages and carburetor thoroughly, use a good carburetor cleaner and follow the manufacturer's instructions. Blow clean, compressed air through the passages and make sure all are open before reassembling. Do not use wire or metal objects to clean passages or carburetor body.

5. Clean all parts as required, use a good carburetor cleaner, following the manufacturer's instructions. Blow clean, compressed air through all the passages. Do not poke or probe into the load block assembly as damage can be done, resulting in serious operational problems. See Figure 5A-7.

Figure 5A-7.

LPG Carburetor - Inspection

1. Inspect the carburetor body and removable venturi (Impco carburetor) for cracks, holes, and other wear or damage.

2. Check the choke shaft (Nikki carburetor only) and the throttle shaft for wear and free movement.

NOTE: Do not attempt to disassemble or

remove either shaft from the carburetor body, including the mounted clamp brackets on Impco style carburetors. The screws, attaching the choke and throttle plate to their respective shafts are staked or bonded to prevent loosening. The plate(s) and shaft(s) are not available separately. If detrimental wear or damage is found in any of the parts, the carburetor should be replaced.

5A.5

Section 5A LPG Fuel Systems

LPG Carburetor - Reassembly

Impco Carburetor

1. Slide the venturi into the carburetor body, aligning the position mark made prior to removal. Correctly installed, the discharge holes should not be visible from the top.

2. Secure with the venturi retaining screw. Torque the screw to 4.0 N·m (36 in. lb.).

3. Install a new adapter gasket and mount the air cleaner adapter onto the carburetor with the four screws. Torque the screws to 4.0 N·m (36 in. lb.).

4. Install a new carburetor gasket onto the intake manifold adapter, followed by the carburetor. Install and finger tighten the mounting fasteners.

5. Connect the ‘‘Z’’ end of the throttle linkage and the dampening spring to the throttle clamp bracket on the throttle shaft. Attach the opposite end of linkage and spring to the governor lever.

NOTE: The clamp brackets and stop collar

mounted on the throttle shaft should still be in their original positions (See Figure 5A-2), and not require any readjustment/ resetting. Continue with steps 6 and 7. If the mounted position of any one of these was affected or changed, it will be necessary to check and reset the position of each before proceeding. Follow the complete instructions listed after step 7, then continue with steps 6 and 7.

Idle Speed Clamp Bracket Position

1. Counting the number of turns, back the idle speed adjustment screw off (counterclockwise), so only 1 to 1 1/2 of the threads are visible. See Figure 5A-8.

Idle Speed Clamp Bracket Mounting Screw

Figure 5A-8. Backing Off Idle Speed Screw.

2. Loosen the clamp bracket mounting screw, and pivot the throttle shaft to fully close the throttle plate. See Figure 5A-9.

6. Manually move the governor lever toward the carburetor as far as it will go.

7. Check that the throttle plate is now fully open or reposition the carburetor slightly on the mounting screws so it is fully open. Torque the mounting screws to 9.9 N·m (88 in. lb.).

Instructions for Checking/Positioning the Clamp Brackets Mounted on the Throttle Shaft

Use only if the position or mounting of the clamp bracket(s) has been disturbed. Figures show the carburetor removed from the engine for clarity.

5A.6

Figure 5A-9. Closing Throttle Plate.

3. Hold the throttle plate closed and rotate the clamp bracket until the end of the screw contacts the stop. Insert a 0.025 mm (0.001 in.) feeler gauge between the carburetor housing and the side of the clamp bracket to set the endplay, then tighten the mounting screw securely. See Figure 5A-10.

Figure 5A-10. Tightening Idle Speed Clamp Mounting Screw.

4. Reset the idle speed adjustment screw back to the original position.

High Speed/Stop Collar Position

1. Make sure the idle speed clamp position has already been checked or properly set.

Section 5A

LPG Fuel Systems

3. Insert a 0.025 mm (0.001 in.) feeler gauge between the side of the stop collar and the carburetor housing, then check or set the position of the stop collar. The head of the mounting screw must be in contact with the carburetor boss from the back (hose/fitting) side, preventing any further rotation over center. Set or adjust the stop collar as required. See Figure 5A-12.

High Speed Stop Collar

Figure 5A-12. Adjusting/Setting Stop Collar .

2. Rotate and hold the throttle shaft so the throttle plate is fully open/perfectly vertical. See Figure 5A-11.

High Speed Stop Collar

Figure 5A-11. Full Throttle Position.

4. Tighten the screw securely.

NOTE: After the idle speed clamp bracket and the

high speed stop collar positions have been set, check that the throttle shaft pivots freely without binding or restriction.

Throttle Linkage Clamp Bracket Position

Carburetor must be assembled to engine with linkage attached to set this position.

1. The throttle linkage clamp bracket should be positioned as shown in Figure 5A-13 on the idle speed clamp bracket side of the throttle shaft.

Throttle Linkage Clamp Bracket

Figure 5A-13. Throttle Linkage Clamp Bracket Position.

5A.7

Section 5A LPG Fuel Systems

2. Manually move the governor lever, with the throttle linkage connected, toward the carburetor as far as it will go. Hold it in this position.

3. Looking down the throat of the carburetor, check that the throttle plate is in the full throttle position and that the head of the high speed collar stop screw is in contact with the carburetor boss. If not, loosen the carburetor mounting screws and reposition the carburetor slightly. Torque the carburetor mounting screws to 9.9 N·m (88 in. lb.).

NOTE: If additional adjustment is required,

loosen the throttle linkage clamp bracket mounting screw, set the throttle shaft to the full throttle position against the head of the stop screw, and retighten the clamp mounting screw securely. See Figure 5A-14.

6. Check to be sure all system connections are tight.

7. Reset idle RPM and recheck high idle (governed speed) after starting and allowing sufficient warm-up time.

Electric Lock-Off/Filter Assembly - Functional Test

The electric lock-off can be easily tested to verify that it is functional. Remove it from the system for testing. Using a 12 volt power supply or battery, connect one wire lead to the positive (+) lead of power supply, and touch remaining wire lead to negative (-) lead of power supply. When connection is made, an audible “click” should be heard indicating the opening of the lock-off. While energized, blow compressed air through it to determine if it is blocked or restricted.

Figure 5A-14. Tightening Throttle Linkage Clamp Bracket.

Nikki Carburetor

1. Reinstall the rear plug with a new sealing washer. Tighten the plug securely.

2. Reinstall fuel transfer chamber cover with a new gasket. Secure with the three screws.

3. Install new carburetor mounting gasket on manifold studs, followed by the carburetor and new air cleaner base gasket.

4. Reconnect the throttle and choke linkages, and the fuel and vacuum lines.

5. Reinstall the air cleaner base and breather tube. Secure base with two mounting nuts. Torque nuts to 9.9 N·m (88 in. lb.). Install the rest of the air cleaner system.

Figure 5A-15.

Figure 5A-16.

Electric Lock-Off/Filter Assembly - Filter Service

The filter inside the lock-off assembly should be replaced every 500 hours of operation, or if it becomes blocked or restricted. Cleaning of the filter element is not recommended. Order a replacement filter element by the appropriate Kohler part number.

5A.8

V aporizer Assembly

The outer surface of the vaporizer should be kept free of dirt and debris accumulation, which will cause a loss of vaporization efficiency. Visual inspection and necessary cleaning should be performed on a regular basis, more frequently under dusty or dirty conditions. The vaporizer should be disassembled, cleaned, and serviced using a rebuild kit every 1500 hours or if a problem is encountered.

Section 5A

LPG Fuel Systems

Figure 5A-18. Impco (Beam) Regulator.

Figure 5A-17.

LPG Regulator

The regulator controls both the pressure and flow of fuel within the LP system. It is comprised of both a primary and secondary chamber, which are dependent upon one another. Two different styles of regulators are used, based upon the system involved. The Impco (Beam) regulator is shown in Figure 5A-18, and the Nikki regulator is shown in Figure 5A-19. Although the basic design and operating principles are similar, due to system differences the regulators should not be interchanged.

Figure 5A-19. Nikki Regulator.

Following are separate sections covering the theory of operation and general service information for each style of regulator. Detailed service/repair instructions are included in the rebuild kit for each regulator.

5A.9

Section 5A LPG Fuel Systems

Impco (Beam) Regulator (See Figure 5A-20)

LPG vapor enters at point (A), then passes into primary area (B) at point (28), where pressure is reduced from up to 250 psi at the tank to 4.5 psi in area (B). Fuel pressure against diaphragm (2) overcomes spring (3) and as movement increases, spring (5) will close lever (6). The primary diaphragm breather (not shown in drawing) is vented to secondary chamber so that rupture of this diaphragm would direct fuel into the carburetor.

Fuel now moves through passage (E), past secondary valve (25) into secondary area (C). As negative pressure (vacuum) is created at the carburetor venturi and is transmitted through the dry-gas hose to chamber (C) secondary diaphragm (12) is drawn down and contacts the secondary lever (16). Fuel will flow in proportion to air velocity through the carburetor venturi, ensuring an ideal mixture at all engine speeds.

Whenever the engine is operating, the vacuum diaphragm (10) is down against the floor (H) and the spring (11) is compressed. The idle and starting adjustment is made with a tamper-resistant screw (17) which regulates the whisker wire system (not shown), opening up the secondary orifice slightly (but only when the vacuum diaphragm is drawn down). Very little vacuum is needed to start this vacuum diaphragm travel: 0.2 in. Mercury to start and 0.5 in. Mercury for full travel. The instant the engine stops rotating, loss of vacuum in section (D) releases diaphragm (10) causing bumper (K) to push against secondary lever (16), overcoming action of whisker wire and ensuring 100% lock-off.

1. 1/8-27 NPT Plug

2. Primary Diaphragm Assembly

3. Primary S pring

4. Expansion Plug

5. Secondary Diaphragm Spring

6. Primary Lever Assembly

7. Fillister Head Screw

8. Primary Pivot Pin

9. Torx Head Screw

10. Vac Lock Diaphragm Assembly

11. Vac Lock Spring

Figure 5A-20.

12. Secondary Diaphragm

13. Pan Head Screw

14. Secondary Lever Spring

15. Secondary Pivot Pin

16. Secondary Lever

17. Adjustment Screw

18. Pan Head Screw

19. Expansion Plug

20. Diaphragm Gasket

21. Split Lock Washer

9 21

Assembly

This patented Beam design will lock off primary pressures up to five times in excess of normal and permits starting without priming or choking.

5A.10

Section 5A

LPG Fuel Systems

Nikki Regulator Primary Chamber (See Figure 5A-21)

The primary chamber reduces the high pressure fuel flow from the tank and vaporizer down to approximately 4 psi. Fuel flowing from the vaporizer enters the inlet of the regulator under approximately 76 kPa (11 psi) of pressure. There it is delivered to the primary chamber (3) through the clearance between the primary valve (1) and valve seat (2). As fuel continues to flow and the primary chamber approaches 29 kPa (4 psi), the primary diaphragm (4) overcomes the tension of the diaphragm spring (5). As the diaphragm (4) and contact button (6) move up, the primary lever spring (8) pushes the primary lever (7) up, in turn closing the primary valve (1) and stopping the flow of fuel. As fuel is consumed and the pressure in the primary chamber drops below 29 kPa (4 psi), the diaphragm spring (5) tension will be greater than the fuel pressure, causing the primary diaphragm (4) to be pushed down. This causes the contact button (6), to push the primary lever (7) down, in turn opening the primary valve (1) and admitting more fuel. In this manner, the pressure within the primary chamber is maintained at a relatively constant 29 kPa (4 psi).

Nikki Regulator Secondary Chamber (See Figure 5A-22)

The secondary chamber further reduces the fuel pressure from the 29 kPa (4 psi) of the primary chamber to near 0 kPa (0 psi) pressure, to prevent excessive fuel flow to the carburetor. Fuel enters the secondary chamber (13) through the clearance between the secondary valve (11) and the valve seat (12). While the engine is operating, and fuel is being drawn from the secondary chamber, the secondary diaphragm (14) is raised by atmospheric pressure, simultaneously lifting the secondary valve lever (16), opening the secondary valve (11), allowing fuel to flow. When the engine is running at idle, there may not be enough vacuum created in the carburetor venturi to overcome the tension of the secondary diaphragm spring (15), and the secondary diaphragm cannot open the valve. Under those conditions, the idle adjusting screw (18), and balance spring (19) are used to apply just enough pressure on the diaphragm (14) to maintain sufficient fuel flow for idle operation.

The vacuum lock-off mechanism is located in the secondary chamber. When the engine is running, manifold vacuum above the diaphragm (17) draws it up, so the secondary valve can function normally. When the engine is stopped, manifold vacuum is terminated, and the diaphragm relaxes and pushes down on the secondary valve lever, preventing any fuel flow or leakage through the regulator.

To Secondary Chamber

1. Primary Valve 6. Contact Button

2. Primary Valve Seat 7. Primary Valve Lever

3. Primary Chamber 8. Primary Lever Spring

4. Primary Diaphragm 9. Primary Pressure

5. Primary Diaphragm Spring Adjustment

Figure 5A-21. Primary Chamber.

Fuel Inlet

From Primary Chamber

To Carburetor

11. Secondary Valve 16. Secondary Valve Lever

12. Secondary Valve Seat 17. Vacuum Lock-Off

13. Secondary Chamber Diaphragm

14. Secondary Diaphragm 18 . Idle Adjust Screw

15. Secondary Diaphragm Spring 19. Balance Spring

To Intake Manifold

Figure 5A-22. Secondary Chamber.

5A.11

Section 5A LPG Fuel Systems

Preventative Maintenance

The regulator is preset at the factory and generally requires no further adjustment. No periodic service is required. Over time, depending on fuel quality, operating environment, and system performance, fuel deposits can accumulate inside the regulator. Those regulators containing a drain plug (Nikki) should be drained every 500 hours to remove any accumulated deposits. See Figure 5A-23.

Regulator Drain Plug

Figure 5A-23. Regulator Drain Plug (Some Models).

Regulator Service

Every 1500 hours it is recommended that disassembly, cleaning, and resetting of the regulator be performed using the regulator rebuilding kit available. Specific instructions are included in the rebuilding kit. Perform the regulator service following the instructions provided. As all adjustments and settings must be reset using specific test equipment, this must be performed by qualified LP personnel only.

Impco (Beam) Regulator Service

Kohler repair kit 24 757 40-S should be used to service the regulator every 1500 hours, or whenever cleaning and servicing is required.

Nikki Regulator Service

Kohler repair kit 24 757 39-S should be used every 1500 hours.

1. Turn supply valve off, run engine out of fuel, and turn off ignition switch.

2. Disconnect and ground the spark plug leads.

3. Remove the 1/8" pipe plug from bottom of regulator and drain any accumulated deposits. See Figure 5A-23.

4. Reinstall plug using pipe sealant with Teflon (Loctite® 592 or equivalent) on threads and tighten securely. If required, a replacement plug is available as Kohler Part No. X-75-23-S.

5A.12

Section 5B

EFI Fuel System

Section 5B

Electronic Fuel Injection (EFI)

Fuel System

Contents Page(s)

Description

Initial Starting/Priming Procedure...................................................................................................................... 5B.2

Fuel Recommendations ........................................................................................................................................ 5B.2

EFI Fuel System Components .............................................................................................................................. 5B.3

Operation ................................................................................................................................................................ 5B.3

Important Service Notes ....................................................................................................................................... 5B.4

Electrical Components

Electronic Control Unit (ECU).................................................................................................................... 5B.4-5B.5

Engine Speed Sensor .................................................................................................................................... 5B.5-5B.6

Throttle Position Sensor (TPS) and Initialization Procedures ............................................................ 5B.7-5B.10

Engine (Oil) Temperature Sensor ........................................................................................................... 5B.10-5B.11

Oxygen Sensor .......................................................................................................................................... 5B.11-5B.13

Electrical Relay ......................................................................................................................................... 5B.13-5B.14

Fuel Injectors ............................................................................................................................................. 5B.14-5B.17

Ignition System ......................................................................................................................................... 5B.17-5B.18

Spark Plugs........................................................................................................................................................... 5B.18

Wiring Harness ........................................................................................................................................ 5B.18-5B.19

Battery Charging System................................................................................................................................... 5B.19

Fuel Components

Fuel Pump ................................................................................................................................................. 5B.19-5B.20

Fuel Pressure Regulator ........................................................................................................................... 5B.20-5B.22

Fuel Filter .............................................................................................................................................................. 5B.22

Fuel Rail ................................................................................................................................................................ 5B.22

Fuel Line .................................................................................................................................................... 5B.22-5B.23

Throttle Body/Intake Manifold Assembly ....................................................................................................... 5B.23

Idle Speed Adjustment (RPM) ................................................................................................................ 5B.23-5B.24

Initial Governor Adjustment................................................................................................................... 5B.24-5B.26

Troubleshooting

Troubleshooting Guide ....................................................................................................................................... 5B.26

Electrical System ....................................................................................................................................... 5B.27-5B.33

Fuel System .......................................................................................................................................................... 5B.34

Fault Codes ................................................................................................................................................ 5B.34-5B.42

Troubleshooting Flow Chart ................................................................................................................... 5B.42-5B.43

Flow Chart Diagnostic Aids .................................................................................................................... 5B.44-5B.45

EFI Service Tools ............................................................................................................................. Refer to Section 2

5B.1

Section 5B EFI Fuel System

Description

WARNING

Explosive Fuel can cause fires and severe burns.

Fuel system ALWAYS remains under HIGH PRESSURE.

WARNING: Explosive Fuel!

The EFI fuel system remains under high pressure, even when the engine is stopped. Before attempting to service any part of the fuel system, the pressure must be relieved. Pressure Tester, (part of EFI Service Kit, see Section 2) has an integral relief valve. Connect the black tester hose to the test valve in the fuel rail. Route the clear hose into a portable gasoline container. Depress the button on the tester relief valve.

Initial Starting/Priming Procedure

Important: The EFI fuel system must be purged of air (primed) prior to the initial start up, and/or any time the system has been disassembled or the fuel tank run dry.

1. Locate the electronic control unit (ECU) for the EFI system. Check the part number on the end. If the Part No. is 24 584 28 or higher, the ECU has a built-in priming feature.

a. Turn the key switch to the “on/run”

position. You will hear the fuel pump cycle on and off. When the fuel pump stops cycling (approximately one minute), the system is primed; start the engine.

2. For plastic-cased ECU’s below 24 584 28-S, the system can be primed by manually cycling the fuel pump.

a. Turn the key switch to the “on/run”

position. The fuel pump will run for about three seconds and stop. Turn the switch off and back on to restart the fuel pump. Repeat this procedure until the fuel pump has cycled five times, then start the engine.

3. The system can also be primed similar to relieving pressure.

a. Connect the pressure gauge as described

above for relieving fuel pressure. Depress and hold the release button and crank the engine until the air is purged and fuel is visible in the discharge tube. If fuel is not visible after 10 seconds, stop cranking and allow the starter to cool for 60 seconds.

Priming Without a Test Valve in Fuel Rail:

1. Crank the engine in 10-15 second intervals, allowing a 60 second cool-down period between cranking intervals, until the engine starts.

NOTE: The number of cranking intervals necessary

will depend on the individual system design, and/or where the system has been disassembled.

Fuel Recommendations

General Recommendations

Purchase gasoline in small quantities and store in clean, approved containers. An approved container with a capacity of 2 gallons or less with a pouring spout is recommended. Such a container is easier to handle and helps prevent spillage during refueling.

• Do not use gasoline left over from the previous season, to minimize gum deposits in your fuel system, and to ensure easy starting.

• Do not add oil to the gasoline.

• Do not overfill the fuel tank. Leave room for the fuel to expand.

Fuel Type

Do not use leaded gasoline, as component damage will result. Any costs/damages incurred as a result of using leaded fuel will not be warranted. Use only clean, fresh, unleaded gasoline with a pump sticker octane rating of 87 or higher. In countries using the Research method, it should be 90 octane minimum.

5B.2

Section 5B

EFI Fuel System

Gasoline/Alcohol blends

Gasohol (up to 10% ethyl alcohol, 90% unleaded gasoline by volume) is approved as a fuel for Kohler EFI engines. Other gasoline/alcohol blends are not approved.

Gasoline/Ether blends

Methyl Tertiary Butyl Ether (MTBE) and unleaded gasoline blends (up to a maximum of 15% MTBE by volume) are approved as a fuel for Kohler EFI engines. Other gasoline/ether blends are not approved.

EFI Fuel System Components

General

The Electronic Fuel Injection (EFI) system is a complete engine fuel and ignition management design. The system includes the following principal components:

• Fuel Pump

• Fuel Filter

• Fuel Rail

• Fuel Line(s)

• Fuel Pressure Regulator

• Fuel Injectors

• Throttle Body/Intake Manifold

• Engine Control Unit (ECU)

• Ignition Coils

• Engine (Oil) Temperature Sensor

• Throttle Position Sensor (TPS)

• Speed Sensor

• Oxygen Sensor

• Wire Harness Assembly & Affiliated Wiring,

• Malfunction Indicator Light (MIL)

Operation

The EFI system is designed to provide peak engine performance with optimum fuel efficiency and lowest possible emissions. The ignition and injection functions are electronically controlled, monitored and continually corrected during operation to maintain the theoretical ideal or “stoichiometric” air/fuel ratio of

14.7:1.

The central component of the system is the Motronic Engine Control Unit (ECU) which manages system operation, determining the best combination of fuel mixture and ignition timing for the current operating conditions.

An electric fuel pump is used to move fuel from the tank through the fuel line and in-line fuel filter. A fuel pressure regulator maintains a system operating pressure of 39 psi and returns any excess fuel to the tank. At the engine, fuel is fed through the fuel rail and into the injectors, which inject it into the intake ports.

™

The ECU controls the amount of fuel by varying the length of time that the injectors are “on.” This can range from 1.5-8.0 milliseconds depending on fuel requirements. The controlled injection of the fuel occurs each crankshaft revolution, or twice for each 4-stroke cycle. One-half the total amount of fuel needed for one firing of a cylinder is injected during each injection. When the intake valve opens, the fuel/ air mixture is drawn into the combustion chamber, ignited, and burned.

The ECU controls the amount of fuel injected and the ignition timing by monitoring the primary sensor signals for engine temperature, speed (RPM), and throttle position (load). These primary signals are compared to preprogrammed “maps” in the ECU computer chip, and the ECU adjusts the fuel delivery to match the mapped values. An oxygen sensor provides continual feedback to the ECU based upon the amount of unused oxygen in the exhaust, indicating whether the fuel mixture being delivered is rich or lean. Based upon this feedback, the ECU further adjusts fuel input to reestablish the ideal air/fuel ratio. This operating mode is referred to as “closed loop” operation. The EFI system operates “closed loop” when all three of the following conditions are met:

a. The oil temperature is greater than 35°C (95°F).

b. The oxygen sensor has warmed sufficiently to

provide a signal (minimum 375°C, 709°F).

c. Engine operation is at a steady state (not starting,

warming up, accelerating, etc.).

During “closed loop” operation the ECU has the ability to readjust temporary and learned adaptive controls, providing compensation for changes in overall engine condition and operating environment, so it will be able to maintain the ideal air/fuel ratio of

14.7:1. The system requires a minimum engine oil temperature greater than 55°C (130°F) to properly adapt. These adaptive values are maintained as long as the ECU is “powered up” by the battery.

During certain operating periods such as cold starts, warm up, acceleration, etc., an air/fuel ratio richer than

14.7:1 is required and the system operates in an “open loop” mode. In “open loop” operation the monitoring of exhaust gases (output) is not used, and the controlling adjustments are based on the primary sensor signals and programmed maps only. The system operates “open loop” whenever the three conditions for closed loop operation (above) are not being met.

5B.3

Section 5B EFI Fuel System

Important Service Notes!

• Cleanliness is essential and must be maintained at all times when servicing or working on the EFI system. Dirt, even in small quantities, can cause significant problems.

• Clean any joint or fitting with parts cleaning solvent before opening to prevent dirt from entering the system.

• Always depressurize the fuel system through the test valve in fuel rail before disconnecting or servicing any fuel system components. See fuel warning on page 5B.2.

• Never attempt to service any fuel system component while engine is running or ignition switch is ‘‘on.’’

• Do not use compressed air if the system is open. Cover any parts removed and wrap any open joints with plastic if they will remain open for any length of time. New parts should be removed from their protective packaging just prior to installation.

Electrical Components

Electronic Control Unit (ECU)

Figure 5B-1. “35 Pin” (MA 1.7) Metal-Cased ECU.

• Avoid direct water or spray contact with system components.

• Do not disconnect or reconnect the wiring harness connector to the control unit or any individual components with the ignition ‘‘on.’’ This can send a damaging voltage spike through the ECU.

• Do not allow the battery cables to touch opposing terminals. When connecting battery cables attach the positive (+) cable to positive (+) battery terminal first, followed by negative (-) cable to negative (-) battery terminal.

• Never start the engine when the cables are loose or poorly connected to the battery terminals.

• Never disconnect battery while engine is running.

• Never use a quick battery charger to start the engine.

• Do not charge battery with key switch ‘‘on.’’

Figure 5B-2. “24 Pin” (MSE 1.0) Plastic-Cased ECU.

Figure 5B-3. “32 Pin” (MSE 1.1) Plastic-Cased ECU.

• Always disconnect negative (-) battery cable lead before charging battery, and also unplug harness from ECU before performing any welding on equipment.

5B.4

Section 5B

EFI Fuel System

Three different styles of ECU’s have been utilized in EFI production. The first style is easily identified by its metal case with large 35 pin connector block, and also as MA 1.7. See Figure 5B-1. The second and third styles have plastic cases, but are smaller in overall size. These have either a 24 pin or 32 pin connector block and identified as MSE 1.0 or MSE 1.1 respectively. See Figures 5B-2 and 5B-3. Basic function and operating control remains the same between the three, however, due to differences in the internal circuitry as well as the wiring harness, none of the ECU’s are interchangeable. Certain individual service/ troubleshooting procedures also apply, where applicable, they are covered individually as: “35 Pin” (MA 1.7) Metal-Cased ECU, “24 Pin” (MSE 1.0) PlasticCased ECU, or “32 Pin” (MSE 1.1) Plastic-Cased ECU.

General

The ECU is the brain or central processing computer of the entire EFI fuel/ignition management system. During operation, sensors continuously gather data which is relayed through the wiring harness to input circuits within the ECU. Signals to the ECU include: ignition (on/off), crankshaft position and speed (RPM), throttle position, oil temperature, exhaust oxygen levels, and battery voltage. The ECU compares the input signals to the programmed maps in its memory to determine the appropriate fuel and spark requirements for the immediate operating conditions. The ECU then sends output signals to set the injector duration and ignition timing.

To prevent engine over-speed and possible failure, a “rev-limiting” feature is programmed into the ECU. If the maximum RPM limit (4125 RPM on MA 1.7, 4500 RPM on MSE 1.0 & MSE 1.1) is exceeded, the ECU suppresses the injection signals, cutting off the fuel flow. This process repeats itself in rapid succession, limiting operation to the preset maximum.

Service

Never attempt to disassemble the ECU. It is sealed to prevent damage to internal components. Warranty is void if the case is opened or tampered with in any way.

All operating and control functions within the ECU are preset. No internal servicing or readjustment may be performed. If a problem is encountered, and you determine the ECU to be faulty, contact your source of supply. Do not replace the ECU without factory authorization.

The relationship between the ECU and the throttle position sensor (TPS) is very critical to proper system operation. If the TPS or ECU is changed, or the mounting position of the TPS is altered, the applicable “TPS Initialization Procedure” (see pages 5B.8 or 5B.9) must be performed to restore the synchronization.

Engine Speed Sensor

The ECU continually performs a diagnostic check of itself, each of the sensors, and the system performance. If a fault is detected, the ECU turns on the Malfunction Indicator Light (MIL) on the equipment control panel, stores the fault code in its fault memory, and goes into a default operating mode. Depending on the significance or severity of the fault, normal operation may continue, or “limp home” operation (slowed speed, richer running) may be initiated. A technician can access the stored fault code using a “blink code” diagnosis flashed out through the MIL. An optional computer software diagnostic program is also available, see Section 2.

The ECU requires a minimum of 7.0 volts to operate. The adaptive memory in the ECU is operational the moment the battery cables are connected, however the adapted values are lost if the battery becomes disconnected for any reason. The ECU will “relearn” the adapted values if the engine is operated for 10-15 minutes at varying speeds and loads after the oil temperature exceeds 55°C (130°F).

Figure 5B-4. Engine Speed Sensor .

5B.5

Section 5B EFI Fuel System

General

The engine speed sensor is essential to engine operation; constantly monitoring the rotational speed (RPM) of the crankshaft. A ferromagnetic 60-tooth ring gear with two consecutive teeth missing is mounted on the flywheel. The inductive speed sensor is mounted

1.5 ± 0.25 mm (0.059 ± 0.010 in.) away from the ring gear. During rotation, an AC voltage pulse is created within the sensor for each passing tooth. The ECU calculates engine speed from the time interval between the consecutive pulses. The two-tooth gap creates an interrupted input signal, corresponding to specific crankshaft position (84° BTDC) for cylinder #1. This signal serves as a reference for the control of ignition timing by the ECU. Synchronization of the inductive speed pickup and crankshaft position takes place during the first two revolutions each time the engine is started. The sensor must be properly connected at all times. If the sensor becomes disconnected for any reason, the engine will quit running.

Service

The engine speed sensor is a sealed, non-serviceable assembly. If “Fault Code” diagnosis indicates a problem within this area, check and test as follows.

1. Check the mounting and air gap of sensor. It must

be 1.5 mm ± 0.25 mm (0.059 ± 0.010 in.).

2. Inspect the wiring and connections for damage or problems.

3. Make sure the engine has resistor type spark plugs.

4. Disconnect main harness connector from ECU.

6. Disconnect the speed sensor connector from wiring harness. It is the connector with one heavy black lead (see Figure 5B-5). Viewing the connector as shown (dual aligning rails on top), test the resistance between the terminals indicated. A reading of 750-1000 be obtained.

Dual Aligning Rails

Corresponds To #3 (MetalCased ECU) or #10 (Plastic-Cased ECU) In Main Connector.

Figure 5B-5. Speed Sensor Connector .

7. a. If the resistance is incorrect, remove the screw

securing the sensor to the mounting bracket andreplace the sensor.

b. If the resistance in step 5 was incorrect, but

the resistance of the sensor alone was correct, test the main harness circuits between the sensor connector terminals and the corresponding pin terminals in the main connector. Correct any observed problem, reconnect the sensor, and perform step 5 again.

Test Terminals

ΩΩ

Ω should again

ΩΩ

Corresponds T o #21 (Metal-Cased ECU) or #9 (Plastic-Cased ECU) In Main Connector.

5. Connect an ohmmeter between the designated pin terminals in the plug:

“35 Pin” (MA 1.7) Metal-Cased ECU: #3 and #21 pin terminals.

“24 Pin” (MSE 1.0) Plastic-Cased ECU: #9 and #10 pin terminals.

“32 Pin” (MSE 1.1) Plastic-Cased ECU: #9 and #10 pin terminals.

See pages 5B.28-5B.33 according to ECU style. A resistance value of 750-1000 temperature (20°C, 68°F) should be obtained. If resistance is correct, check the mounting, air gap, toothed ring gear (damage, runout, etc.), and flywheel key.

5B.6

ΩΩ

Ω at room

ΩΩ

Section 5B

EFI Fuel System

Throttle Position Sensor (TPS)

Mounted on the throttle body/intake manifold and operated directly off the end of the throttle shaft, the TPS works like a rheostat, varying the voltage signal to the ECU in direct correlation to the angle of the throttle plate. This signal, along with the other sensor signals, is processed by the ECU and compared to the internal preprogrammed maps to determine the required fuel and ignition settings for the amount of load.

The correct position of the TPS is established and set at the factory. Do not loosen the TPS or alter the mounting position unless absolutely required by fault code diagnosis or throttle shaft service. If the TPS is loosened or repositioned the appropriate “TPS Initialization Procedure” (pages 5B.8-5B.10) must be performed to reestablish the baseline relationship between the ECU and the TPS.

Service

The TPS is a sealed, non-serviceable assembly. If diagnosis indicates a bad sensor, complete replacement is necessary. If a blink code indicates a problem with the TPS, it can be tested as follows:

1. Throttle V alve Shaft

2. Resistor Track

3. Wiper Arm w/Wiper

4. Electrical Connection

Figure 5B-6. Throttle Position Sensor Details.

General

The throttle position sensor (TPS) is used to indicate throttle plate angle to the ECU. Since the throttle (by way of the governor) reacts to engine load, the angle of the throttle plate is directly proportional to the load on the engine.

Mounted Throttle Position Sensor

Figure 5B-7. TPS Location.

1. Counting the number of turns, back out the idle speed adjusting screw (counterclockwise) until the throttle plates can be closed completely.

2. Disconnect the main harness connector from the ECU, but leave the TPS mounted to the throttle body/manifold.

3. Connect the ohmmeter leads as follows: (See chart on pages 5B.28, 5B.31, or 5B.32).

“35 Pin” (MA 1.7) Metal-Cased ECU: Red (positive) ohmmeter lead to #12 pin terminal, and Black (negative) ohmmeter lead to #27 pin terminal.

“24 Pin” (MSE 1.0) Plastic-Cased ECU: Red (positive) ohmmeter lead to #8 pin terminal, and Black (negative) ohmmeter lead to #4 pin terminal.

“32 Pin” (MSE 1.1) Plastic-Cased ECU: Red (positive) ohmmeter lead to #8 pin terminal, and Black (negative) ohmmeter lead to #4 pin terminal.

Hold the throttle closed and check the resistance. It should be 800-1200

ΩΩ

Ω.

ΩΩ

5B.7

Section 5B EFI Fuel System

4. Leave the leads connected to the pin terminals as described in step 3. Rotate the throttle shaft slowly counterclockwise to the full throttle position. Monitor the dial during rotation for indication of any momentary short or open circuits. Note the resistance at the full throttle position. It should be 1800-3000

5. Disconnect the main wiring harness connector from the TPS, leaving the TPS assembled to the manifold. Refer to the chart below and perform the resistance checks indicated between the terminals in the TPS switch, with the throttle in the positions specified.

Throttle

Position

Closed

Full Full

Any

If the resistance values in steps 3, 4, and 5 are within specifications, go to step 6.

If the resistance values are not within specifications, or a momentary short or open circuit was detected during rotation (step 4), the TPS needs to be replaced, go to step 7.

Between

Terminals

2 & 3 1 & 3 2 & 3 1 & 3 1 & 2

Resistance

Value (Ω)

800-1200 1800-3000 1800-3000

800-1200 1600-2500

ΩΩ

Ω.

ΩΩ

Continuity

Yes Yes Yes Yes Yes

7. Remove the two mounting screws from the TPS. Save the screws for reuse. Remove and discard the faulty TPS. Install the replacement TPS and secure with the original mounting screws.

a. Reconnect both connector plugs.

b. Perform the appropriate “TPS Initialization

Procedure” integrating the new sensor to the ECU.

TPS Initialization Procedure

For “35 Pin” (MA 1.7) Metal-Cased ECU and

“24 Pin” (MSE 1.0) Plastic-Cased ECU only

1. Check that the basic engine, all sensors, fuel, fuel pressure, and battery are good and functionally within specifications.

Important!

2. Remove/disconnect ALL external loads from engine (belts, pumps, electric PTO clutch, alternator, rectifier-regulator, etc.).

3. Start the engine and allow it to warm up for 5-10 minutes, so oil temperature is above 55°C (130°F).

4. Move the throttle control to the idle position and allow engine to stabilize for a minimum of one minute.

6. Check the TPS circuits (input, ground) between the TPS plug and the main harness connector for continuity, damage, etc. See chart on pages 5B.28, 5B.31, or 5B.32.

“35 Pin” (MA 1.7) Metal-Cased ECU: Pin Circuits #12 and #27.

“24 Pin” (MSE 1.0) Plastic-Cased ECU: Pin Circuits #8 and #4.

“32 Pin” (MSE 1.1) Plastic-Cased ECU: Pin Circuits #8 and #4.

a. Repair or replace as required.

b. Turn the idle speed screw back in to its

original setting.

c. Reconnect connector plugs, start engine and

retest system operation.

5. Install a heavy rubber band around the throttle lever and the manifold boss, to firmly hold the throttle against the idle stop. On some EFI engines there is a dampening spring on the end of the idle speed screw. The dampening spring (if used) should be fully compressed and the tab on the throttle lever in direct contact with the speed screw. Adjust the idle speed to 1500 RPM, using a tachometer.

6. Shut off engine.

7. Locate the service connector plug in the wiring harness.

“35 Pin” (MA 1.7) Metal-Cased ECU: Connect a jumper wire from the TPS initialization pin #8 (gray wire) to the ground pin (black wire), or use the jumper plug with the red jumper wire. See Figure 5B-8.

5B.8

Section 5B

EFI Fuel System

“24 Pin” (MSE 1.0) Plastic-Cased ECU: Connect a jumper wire from the TPS initialization pin #24 (violet wire) to the battery voltage pin (red wire), or use the jumper plug with the blue jumper wire. See Figure 5B-9.

Figure 5B-8. Service Connector Plug, Metal-Cased ECU Harness.

b. If light stays on or blinking ceases

prematurely, the procedure was unsuccessful and must be repeated. Possible causes for unsuccessful learning may be: 1) Movement occurred in either the TPS or throttle shaft during procedure, 2) Crankshaft movement/ rotationwas detected by the speed sensor during procedure, 3) Throttle plate position was out of learnable range (recheck the 1500 RPM idle speed adjustment), or 4) Problem with ECU or TPS.

9. When the initialization procedure has been successfully completed, turn off the key switch, remove the jumper wire or connector, and remove the rubber band from the throttle lever.

10. Disconnect negative (-) battery cable temporarily to clear all learned adjustments.

11. Reconnect the battery cable and all external loads. Readjust the idle speed to the equipment manufacturer’s specified setting and recheck the high-speed, no-load RPM setting. Observe the overall performance.

Figure 5B-9. Service Connector Plug, PlasticCased ECU Harness.

8. Hold throttle against idle speed stop screw, turn the ignition switch to “on” position (do not start engine), and observe the Malfunction Indicator Light (MIL).

a. The light should blink on/off quickly for

approximately 3 seconds and then go off and stay off, indicating the initialization procedure has been successful.

TPS Initialization Procedure

For “32 Pin” (MSE 1.1) Plastic-Cased ECU Only

(“Auto-Learn” Initialization)

1. Check that the basic engine, all sensors, fuel, fuel pressure, and battery are good and functionally within specifications.

Important!

2. Remove/disconnect ALL external loads from the engine (belts, pumps, electric PTO clutch, alternator, rectifier-regulator, etc.).

3. Locate the service connector plug in the wiring harness. To initiate the TPS auto-learn function, connect a jumper wire from the TPS initialization pin #24 (violet wire) to the battery voltage pin (red wire), or use the jumper plug with the blue jumper wire. If using the PC-based diagnostic tool and software (see Section 2), go to “Special Tests” and follow the prompts to complete.

4. Start the engine and immediately observe the Malfunction Indicator Light (MIL). The light should start blinking 4 consecutive times every 2 seconds.

5B.9

Section 5B EFI Fuel System

5. Remove the jumper wire or plug from the service connector plug in wiring harness.

6. Run the engine at full throttle (above 3000 RPM), to warm up the engine and initiate O function in “closed-loop” operation.

7. Watch the “MIL”. When the light starts blinking rapidly, (5 blinks per second), move the throttle lever to the low idle speed position. Check and adjust the idle speed to 1500 RPM, using a tachometer. The lamp should continue to blink rapidly for another 30 seconds before switching to a slow blink.

8. When the “MIL” blinks slowly, do not do anything but wait until the “MIL” shuts off. This indicates that this procedure has been completed successfully.

9. Shut off the engine.

If the learn procedure was successfully completed, the external loads removed/ disconnected in Step 2 may be reconnected.

If the procedure was unsuccessful see Steps a. and b. following.

a. If during this procedure, the “MIL” goes back

into blinking 4 consecutive blinks every 2 seconds, the engine and O cooled down and out of “closed-loop” operation, prohibiting the learning from occurring. Repeat Steps 6-9.

b. If during the procedure with the engine

running, the “MIL” stays “on” continuously, for more than 15 seconds, turn off the ignition. Then initiate the fault code sequence, by doing three consecutive key-on/key-off cycles leaving the key “on” in the last sequence, (each key-on/key-off sequence must be less than 2.5 seconds long). The fault detected must be corrected before the “auto-learn” function can be re-initiated. The PC-based diagnostic tool and software may be used to read out the fault code and assist with the troubleshooting and repair.

sensor have

sensor

Engine (Oil) T emperature Sensor

Figure 5B-10. Engine (Oil) T emperature Sensor.

General

The engine (oil) temperature sensor (Figure 5B-10) is used by the system to help determine fuel requirements for starting, (a cold engine needs more fuel than one at or near operating temperature). Mounted in the oil filter adapter housing, it has a temperature-sensitive resistor that extends into the oil flow. The resistance changes with oil temperature, altering the voltage sent to the ECU. Using a table stored in its memory, the ECU correlates the voltage drop to a specific temperature. Using the fuel delivery “maps”, the ECU then knows how much fuel is required for starting at that temperature.

Service

The temperature sensor is a sealed, non-serviceable assembly. A faulty sensor must be replaced. If a blink code indicates a problem with the temperature sensor, it can be tested as follows:

1. Remove the oil temperature sensor from the adapter housing and cap or block the adapter hole.

2. Wipe sensor clean and allow it to reach room temperature (20°C, 68°F).

3. Unplug the main harness connector from the ECU.

4. With the sensor connected, check the oil temperature sensor circuit resistance. The value should be 2375-2625 5B.31, or 5B.32.

ΩΩ

Ω. See chart on pages 5B.28,

ΩΩ

5B.10

“35 Pin” (MA 1.7) Metal-Cased ECU: Check between the #14 and #27 pin terminals.

Section 5B

EFI Fuel System

“24 Pin” (MSE 1.0) Plastic-Cased ECU: Check between the #6 and #4 pin terminals.

“32 Pin” (MSE 1.1) Plastic-Cased ECU: Check between the #6 and #4 pin terminals.

5. Unplug the sensor connector and check sensor resistance separately. Resistance value should again be 2375-2625

a. If the resistance is out of specifications,

replace the temperature sensor.

b. If it is within specifications, proceed to Step 6.

6. Check the temperature sensor circuits (input, ground) from the main harness connector to the corresponding terminal in the sensor plug for continuity, damage, etc.

“35 Pin” (MA 1.7) Metal-Cased ECU: Pin circuits #14 and #27.

“24 Pin” (MSE 1.0) Plastic-Cased ECU: Pin circuits #6 and #4.

ΩΩ

Ω.

ΩΩ

The tip of the sensor, protruding into the exhaust gas, is hollow (see cutaway Figure 5B-12). The outer portion of the tip is surrounded by the exhaust gas, with the inner portion exposed to the ambient air. When the oxygen concentration on one side of the tip is different than that of the other side, a voltage signal typically cycling between 0.2 and 1.0 volt is generated between the electrodes and sent to the ECU. The voltage signal tells the ECU if the engine is straying from the ideal 14.7:1 fuel mixture, and the ECU then adjusts the injector pulse accordingly.

1. Connection Cable

2. Disc Spring

3. Ceramic Support Tube

4. Protective Sleeve

5. Contact Element

6. Sensor Housing

7. Active Ceramic Sensor

8. Protective Tube

“32 Pin” (MSE 1.1) Plastic-Cased ECU: Pin circuits #6 and #4.

Oxygen Sensor

Figure 5B-11. Oxygen Sensor .

General

The oxygen sensor functions like a small battery, generating a voltage signal to the ECU, based upon the difference in oxygen content between the exhaust gas and the ambient air.

Figure 5B-12. Cutaway of Oxygen Sensor .

The oxygen sensor can function only after being heated by exhaust temperatures to a minimum of 375°C (709°F). A cold oxygen sensor will require approximately 1-2 minutes at moderate engine load to warm sufficiently to generate a voltage signal. Proper grounding is also critical. The oxygen sensor grounds through the metal shell, so a good, solid, unbroken ground path back through the exhaust system components, engine, and wiring harness is required. Any disruption or break in the ground circuit can affect the output signal and trigger misleading fault codes. Keep that in mind when doing any troubleshooting associated with the oxygen sensor. The oxygen sensor can also be contaminated by leaded fuel, certain RTV and/or other silicone compounds, carburetor cleaners, etc. Use only those products indicated as “O² Sensor Safe.”

Service

Like the other sensors already discussed, the oxygen sensor is a non-serviceable component. Complete replacement is required if it is faulty. The sensor and wiring harness can be checked as follows.

NOTE: All tests should be conducted with a good

quality, high-impedance, digital VOA meter for accurate results.

5B.11

Section 5B EFI Fuel System

1. Oxygen sensor must be hot (minimum of 400°C, 725°F). Run engine for about 5 minutes. With the engine running, disconnect the oxygen sensor lead from the wiring harness. Set VOA meter for DC volts and connect the red lead to the disconnected sensor lead, and the black lead to the sensor shell. Check for a voltage reading between 0.2 v-1.0 v.

a. If voltage is in the specified range, go to Step 2.

b. If the voltage is not in the specified range,

reconnect the oxygen sensor lead. With the lead connected, probe or connect the sensor connection with the red VOA meter lead. Attach the black VOA meter lead to a known good ground location. Start and run the engine at 3/4 throttle and note the voltage output.

The reading should cycle between 0.2 v-1.0 v, which indicates the oxygen sensor is functioning normally and also the fuel delivery controlled by the ECU is within prescribed parameters. If the voltage readings show a steady decline, bump the governor lever to make the engine accelerate very quickly and check the reading again. If voltage momentarily increases and then again declines, without cycling, engine may be running lean due to incorrect TPS initialization. Shut off the engine, perform TPS initialization, and then repeat the test. If TPS initialization cannot be achieved, perform step c.

previous checkpoint. For example, if the reading is too low at points on the crankcase, but correct voltage is indicated when the black lead is touched to the skin of the muffler, the flange joints at the exhaust ports become suspect.

3. With sensor still hot (minimum of 400°C, 752°F), switch meter to the Rx1K or Rx2K scale and check the resistance between the sensor lead and sensor

ΩΩ

Ω.

ΩΩ

Ω.

ΩΩ

Ω, go to

ΩΩ

Ω, the

ΩΩ

Ω, go to

ΩΩ

Ω, the

ΩΩ

case. It should be less than 2.0 K

a. If the resistance is less than 2.0 K

Step 4.

b. If the resistance is greater than 2.0 K

oxygen sensor is bad, replace it.

4. Allow the sensor to cool (less than 60°C, 140°F) and retest the resistance with the meter set on the Rx1M scale. With sensor cool, the resistance should be greater than 1.0 M

a. If the resistance is greater than 1.0 M

Step 5.

b. If the resistance is less than 1.0 M

sensor is bad, replace it.

5. With the oxygen sensor disconnected and engine not running, disconnect the main harness connector from the ECU and set the meter to the Rx1 scale. Check the circuit continuity as follows:

c. Replace the oxygen sensor (page 5B.13). Run

the engine long enough to bring the new sensor up to temperature and repeat the output test from step 1. The cycling voltage from 0.2 to 1.0 volt should be indicated.

2. Move the black voltmeter lead to the engine

ground location and repeat the output test. The same voltage (0.2 v-1.0 v) should be indicated.

a. If the same voltage reading exists, go on to

Step 3.

b. If the voltage output is no longer correct, a bad

ground path exists between the sensor and the engine ground. Touch the black lead at various points, backtracking from the engine ground back toward the sensor, watching for a voltage change at each location. If the correct voltage reading reappears at some point, check for a problem (rust, corrosion, loose joint or connection) between that point and the

5B.12

“35 Pin” (MA 1.7) Metal-Cased ECU: Check for continuity from pin #9 of the ECU connector (see page 5B.28) to the shell of the oxygen sensor, and from pin #10 to the sensor connector terminal of the main harness. Both tests should indicate continuity.

“24 Pin” (MSE 1.0) Plastic-Cased ECU: Check for continuity from pin #15 of the ECU connector (see page 5B.31) to the shell of the oxygen sensor, and from pin #11 to the sensor connector terminal of the main harness. Both tests should indicate continuity.

“32 Pin” (MSE 1.1) Plastic Cased ECU: Check for continuity from pin #19 of the ECU connector (see page 5B.32) to the shell of the oxygen sensor, and from pin #20 to the sensor terminal of the main harness. Both tests should indicate continuity.

Section 5B

EFI Fuel System

a. If there is no continuity displayed in either of

the tests, check the harness circuit for breaks or damage, and the connections for poor contact, moisture, or corrosion. If no continuity was found in the first test, also check for a poor/broken ground path back through the exhaust system, engine, and mounting (sensor is grounded through its shell).

b. If continuity is indicated, go to step 6.

6. With the key switch in the ‘‘on/run’’ position, using a high impedance voltmeter, check the voltage from the wiring harness oxygen sensor connector to the engine ground location. Look for a steady voltage from 350-550 mv (0.35-0.55 v).

a. If voltage reading is not as specified, move the

black voltmeter lead to the negative post of the battery, to be certain of a good ground. If the voltage is still not correct, the ECU is probably bad.

b. If voltage readings are correct, clear the fault

codes and run the engine to check if any fault codes reappear.

T o Replace Oxygen Sensor

1. Disconnect the oxygen sensor connector from wiring harness.

2. Loosen and remove the oxygen sensor from the exhaust manifold/muffler assembly.

3. Apply anti-seize compound sparingly to threads of new oxygen sensor, if none already exists. DO NOT get any on the tip as it will contaminate the sensor. Install sensor and torque to 50-60 N·m (37-44 ft. lb.).

4. Reconnect the lead to wiring harness connector. Make sure it can not contact hot surfaces, moving parts, etc.

Electrical Relay

Figure 5B-13. Electrical Relay .

General

The electrical relay is used to supply power to the injectors, coils, and fuel pump. When the key switch is turned “on” and all safety switch requirements met, the relay provides 12 volts to the fuel pump circuit, injectors, and ignition coils. The fuel pump circuit is continuously grounded, so the pump is immediately activated and pressurizes the system. Activation of the ignition coils and injectors is controlled by the ECU, which grounds their respective circuits at the proper times.

Service

A malfunctioning relay can result in starting or operating difficulties. The relay and related wiring can be tested as follows:

1. Disconnect the relay connector plug from the relay.

2. Connect black lead of VOA meter to a chassis ground location. Connect red lead to the #86 terminal in relay connector (see Figure 5B-14). Set meter to test resistance (Rx1). Turn ignition switch from “off” to “on”. Meter should indicate continuity (ground circuit is completed) for 1 to 3 seconds. Turn key switch back off.

5. Test run the engine.

5B.13

Section 5B EFI Fuel System

Terminal #85 Ignition Switch Voltage

Terminal #87A Not used

Terminal #30 Permanent Battery Voltage

Terminal #87 Feed T o Ignition Coils, Fuel Injectors, and Fuel Pump

Terminal #86 ECU Controlled Ground

Figure 5B-14. Relay Connector.

a. Clean the connection and check wiring if

circuit was not completed.

3. Set meter for DC voltage. Touch red tester lead to the #30 terminal in relay connector. A reading of 12 volts should be indicated at all times.

4. Connect red lead of meter to the #85 terminal in relay connector. Turn key switch to the “on” position. Battery voltage should be present.

6. Attach ohmmeter leads to the #30 and #87 terminals in relay. Initially, there should be no continuity. Using a 12 volt power supply, connect the positive (+) lead to the #85 terminal, and touch the negative (-) lead to the #86 terminal. When 12 volts is applied, the relay should activate and continuity should exist (circuit made) between the #30 and #87 terminals. Repeat the test several times. If, at any time the relay fails to activate the circuit, replace the relay.

Fuel Injectors

a. No voltage present indicates a problem in the

wiring or at the connector.

b. If voltage is present, the wiring to the

connector is good. Turn ignition switch ‘‘off’’ and proceed to test 5 to test the relay.

T erminal #86 ECU Controlled Ground

T erminal #87 - Feed

to Ignition Coils,

Fuel Injectors,

and Fuel Pump

T erminal #85 Terminal #87A -

Ignition

Switch V olt age Not Used

T erminal #30 Permanent Battery V oltage

Figure 5B-15. Relay Terminal Details.

5. Connect an ohmmeter (Rx1 scale) between the

#85 and #86 terminals in the relay. There should be continuity. See Figure 5B-15.

Figure 5B-16. Style 1 Fuel Injector.

Figure 5B-17. Style 2 Fuel Injector.

General

The fuel injectors mount into the intake manifold, and the fuel rail attaches to them at the top end. Replaceable O-Rings on both ends of the injector prevent external fuel leakage, and also insulate it from heat and vibration. A special clip connects each injector to the fuel rail, retaining it in place.

5B.14

Section 5B

EFI Fuel System

When the key switch is on and the relay is closed, the fuel rail is pressurized, and voltage is present at the injector. At the proper instant, the ECU completes the ground circuit, energizing the injector. The valve needle in the injector is opened electromagnetically, and the pressure in the fuel rail forces fuel down through the inside. The “director plate” at the tip of the injector (see inset) contains a series of calibrated openings which directs the fuel into the manifold in a cone-shaped spray pattern.

Service

Injector problems typically fall into three general categories: electrical, dirty/clogged, or leakage. An electrical problem usually causes one or both of the injectors to stop functioning. Several methods may be used to check if the injectors are operating.

1. With the engine running at idle, feel for operational vibration, indicating that they are opening and closing.

2. When temperatures prohibit touching, listen for a buzzing or clicking sound with a screwdriver or mechanic’s stethoscope (see Figure 5B-19).

Listen Here

Multi-Orifice Director Plate with Calibrated Opening

1. Filter strainer in fuel supply

2. Electrical connection

3. Solenoid winding

4. V alve housing

Figure 5B-18. Fuel Injector Details.

The injector is opened and closed once for each crankshaft revolution, however, only one-half the total amount of fuel needed for one firing is injected during each opening. The amount of fuel injected is controlled by the ECU and determined by the length of time the valve needle is held open, also referred to as the “injection duration” or “pulse width”. It may vary in length from 1.5-8 milliseconds depending on the speed and load requirements of the engine.

5. Armature

6. V alve body

7. V alve needle

Figure 5B-19. Checking Injectors.

3. Disconnect the electrical connector from an injector and listen for a change in idle performance (only running on one cylinder) or a change in injector noise or vibration.

If an injector is not operating, it can indicate either a bad injector, or a wiring/electrical connection problem. Check as follows:

NOTE: Do not apply voltage to the fuel injector(s).

Excessive voltage will burn out the injector(s). Do not ground the injector(s) with the ignition “on”. Injector(s) will open/turn on if relay is energized.

1. Disconnect the electrical connector from both injectors. Plug the 12 volt Noid Light (part of EFI Service Kit, see Section 2) in one connector.

5B.15

Section 5B EFI Fuel System

Figure 5B-20. V olt Noid Light.

2. Make sure all safety switch requirements are met. Crank the engine and check for flashing of noid light. Repeat test at other connector.

Check all electrical connections, connectors, and wiring harness leads if resistance is incorrect.

Injector leakage is very unlikely, but in those rare instances it can be internal (past the tip of the valve needle), or external (weeping around the injector body). See Figure 5B-21. The loss of system pressure from the leakage can cause hot restart problems and longer cranking times. To check for leakage it will be necessary to remove the blower housing, which may involve removing the engine from the unit.

a. If flashing occurs, use an ohmmeter (Rx1

scale) and check the resistance of each injector across the two terminals. Proper resistance is 12-20 correct, check whether the connector and injector terminals are making a good connection. If the resistance is not correct, replace the injector following steps 1-8 and 13-16 below.

b. If no flashing occurs, reattach connectors to

both injectors. Disconnect the main harness connector from the ECU and the connector from the relay. Set the ohmmeter to the Rx1 scale and check the injector circuit resistance as follows:

“35 Pin” (MA 1.7) Metal-Cased ECU: Check the resistance between the relay terminal #87 and pin #35 in main connector. Resistance should be 4-15

“24 Pin” (MSE 1.0) Plastic-Cased ECU:

Check the resistance between relay terminal #87 and pin #16 in main connector. Then check resistance between relay terminal #87 and pin #17. Resistance should be 4-15 each circuit.

“32 Pin” (MSE 1.1) Plastic-Cased ECU:

Check the resistance between relay terminal #87 and pin #14 in the main connector. Then check the resistance between relay terminal

#87 and pin #15. Resistance should be 4-15 for each circuit.

ΩΩ

Ω. If injector resistance is

ΩΩ

Ω.

ΩΩ

Ω for

ΩΩ

Ω

ΩΩ

Check For Leaks

Figure 5B-21. Injector Inspection Points.

1. Engine must be cool. Depressurize fuel system through test valve in fuel rail.

2. Disconnect spark plug leads from spark plugs.

3. Remove the air cleaner outer cover, inner wing nut, element cover and air cleaner element/ precleaner. Service air cleaner components as required.

4. Remove the two screws securing the air cleaner base to throttle body manifold. Remove the air cleaner base to permit access to the injectors. Check condition of air cleaner base gasket, replace if necessary.

5. Remove the flywheel screen if it overlaps the blower housing.

6. If the engine has a radiator-type oil cooler mounted to the blower housing, remove the two oil cooler mounting screws.

7. Remove the blower housing mounting screws. Note the location of the plated (silver) screw attaching the rectifier-regulator ground lead. Remove the blower housing.

5B.16

Section 5B

EFI Fuel System

8. Thoroughly clean the area around and including the throttle body/manifold and the injectors.

9. Disconnect the throttle linkage and damper spring from the throttle lever. Disconnect the TPS lead from the harness.

10. Remove the manifold mounting bolts and separate the throttle body/manifold from the engine leaving the TPS, fuel rail, air baffle, injectors and line connections intact. Discard the old gaskets.

11. Position the manifold assembly over an appropriate container and turn the key switch “on” to activate the fuel pump and pressurize the system. Do not turn switch to “start” position.

12. If either injector exhibits leakage of more than two to four drops per minute from the tip, or shows any sign of leakage around the outer shell, turn the ignition switch off and replace injector as follows.

13. Depressurize the fuel system following the procedure in the fuel warning on page 5B.2. Remove the two fuel rail mounting screws.

14. Clean any dirt accumulation from the sealing/ mounting area of the faulty injector(s) and disconnect the electrical connector(s).

injector clogging include higher than normal operating temperatures, short operating intervals, and dirty, incorrect, or poor quality fuel. Cleaning of clogged injectors is not recommended; they should be replaced. Additives and higher grades of fuel can be used as a preventative measure if clogging has been a problem.

Ignition System

General

A high voltage, solid state, battery ignition system is used with the EFI system. The ECU controls the ignition output and timing through transistorized control of the primary current delivered to the coils. Based on input from the speed sensor, the ECU determines the correct firing point for the speed at which the engine is running. At the proper instant, it releases the flow of primary current to the coil. The primary current induces high voltage in the coil secondary, which is then delivered to the spark plug. Each coil fires every revolution, but every other spark is “wasted.”

Service

Except for removing the spark plug lead by unscrewing it from the secondary tower (see Figure 5B-22), no coil servicing is possible. If a coil is determined to be faulty, replacement is necessary. An ohmmeter may be used to test the wiring and coil windings.

15. Pull the retaining clip off the top of the injector(s) and remove from manifold.

16. Reverse the appropriate procedures to install the new injector(s) and reassemble the engine. Use new O-Rings any time an injector is removed (new replacement injectors include new O-Rings). Lubricate O-Rings lightly with oil. Torque the fuel rail and blower housing mounting screws to

3.9 N·m (35 in. lb.), and the intake manifold and air cleaner mounting screws to 9.9 N·m (88 in. lb.).

Injector problems due to dirt or clogging are generally unlikely, due to the design of the injectors, the high fuel pressure, and the detergent additives in the gasoline. Symptoms that could be caused by dirty/ clogged injectors include rough idle, hesitation/ stumble during acceleration, or triggering of fault codes related to fuel delivery. Injector clogging is usually caused by a buildup of deposits on the director plate, restricting the flow of fuel, resulting in a poor spray pattern. Some contributing factors to

Figure 5B-22. Ignition Coil.

NOTE: Do not ground the coils with the ignition

‘‘on,’’ as they may overheat or spark.

T esting

1. Disconnect the main harness connector from ECU.

“35 Pin” (MA 1.7) Metal-Cased ECU: Locate pins #1 and #19 in the 35 pin connector. See page 5B.28.

5B.17

Section 5B EFI Fuel System

“24 Pin” (MSE 1.0) Plastic-Cased ECU: Locate pins #22 and #23 in the 24 pin connector. See page 5B.31.

“32 Pin” (MSE 1.1) Plastic Cased ECU: Locate pins #30 and #31 in the 32 pin connector. See page 5B.32.

2. Disconnect connector from relay and locate terminal #87 in connector.

3. Using an ohmmeter set on the Rx1 scale, check the resistance in circuits as follows:

“35 Pin” (MA 1.7) Metal-Cased ECU: Check between terminal #87 and pin #1 for coil #1. Repeat the test between terminal #87 and pin #19 for coil #2.

“24 Pin” (MSE 1.0) Plastic-Cased ECU: Check between terminal #87 and pin #22 for coil #1. Repeat the test between terminal #87 and pin #23 for coil #2.

“32 Pin” (MSE 1.1) Plastic-Cased ECU: Check between terminal #87 and pin #30 for coil #1. Repeat the test between terminal #87 and pin #31 for coil #2.

A reading of 1.8-4.0 the wiring and coil primary circuits are OK.

ΩΩ

Ω in each test indicates that

ΩΩ

4. If the secondary resistance is not within the specified range, unscrew the spark plug lead nut from the coil secondary tower and remove the plug lead. Repeat step b. 3, testing from the secondary tower terminal to the red primary terminal. If resistance is now correct, the coil is good, but the spark plug lead is faulty, replace the lead. If step b. 2 resistance was incorrect and/or the secondary resistance is still incorrect, the coil is faulty and needs to be replaced.

Spark Plugs

EFI engines are equipped with Champion® RC12YC (Kohler Part No. 12 132 02-S) resistor style spark plugs. Equivalent alternate brand plugs can also be used, but must be a resistor style plug or permanent damage to the ECU will occur in addition to affecting operation. Proper spark plug gap is 0.76 mm (0.030 in.).

Wiring Harness

The wiring harness used in the EFI system connects the electrical components, providing current and ground paths for the system to operate. All input and output signaling occurs through a special all weather connector that attaches and locks to the ECU (see Figures 5B-23, 5B-24, and 5B-25).

a. If reading(s) are not within specified range,

check and clean connections and retest.

b. If reading(s) are still not within the specified

range, test the coils separately from main harness as follows:

1. Disconnect the red and black primary leads from the coil terminals.

2. Connect an ohmmeter set on the Rx1 scale to the primary terminals. Primary

ΩΩ

Ω.

ΩΩ

5B.18

resistance should be 1.8-2.5

3. Disconnect the secondary lead from the spark plug. Connect an ohmmeter set on the Rx10K scale between the spark plug boot terminal and the red primary terminal. Secondary resistance should be

13,000-17,500

ΩΩ

Ω.

ΩΩ

Figure 5B-23. “35 Pin” (MA 1.7) Metal-Cased ECU Connector and O-Ring.

Fuel Components

Fuel Pump

Section 5B

EFI Fuel System

Figure 5B-24. “24 Pin” (MSE 1.0) Plastic-Cased ECU Connector.

Figure 5B-25. “32 Pin” (MSE 1.1) Plastic-Cased ECU Connector.

The condition of the wiring, connectors, and terminal connections is essential to system function and performance. Corrosion, moisture, and poor connections are more likely the cause of operating problems and system errors than an actual component. Refer to the ‘‘Troubleshooting – Electrical’’ section for additional information.

Battery Charging System

EFI engines are equipped with either a 15 or 25 amp charging system to accommodate the combined electrical demands of the ignition system and the specific application. Charging system troubleshooting information is provided in Section 8.

Internal

Figure 5B-26. Fuel Pump Styles.

General

An electric fuel pump is used to transfer fuel in the EFI system. Depending on the application, the pump may be inside the fuel tank, or in the fuel line near the tank. The pumps are rated for a minimum output of 25 liters per hour at 39 psi. The pumps have an internal 60-micron filter. In addition, the in-tank style pumps will have a pre-filter attached to the inlet. Inline pump systems may also have a filter ahead of the pump on the pick-up/low pressure side. The final filter is covered separately on page 5B.22.

When the key switch is turned “on” and all safety switch requirements are met, the ECU through the relay, activates the fuel pump, which pressurizes the system for start-up. If the key switch is not promptly turned to the “start” position, the engine fails to start, or the engine is stopped with the key switch “on” (as in the case of an accident), the ECU switches off the pump preventing the continued delivery of fuel. In this situation, the MIL will go on, but it will go back off after 4 cranking revolutions if system function is OK. Once the engine is running, the fuel pump remains on.

Service

The fuel pumps are non-serviceable and must be replaced if determined to be faulty. If a fuel delivery problem is suspected, make certain the pump is being activated through the relay, all electrical connections are properly secured, the fuses are good, and a minimum of 7.0 volts is being supplied. If during cranking, voltage drops below 7.0 volts, a reduction of fuel pressure may occur resulting in a lean starting condition. If required, testing of the fuel pump and relay may be conducted.

External

5B.19

Section 5B EFI Fuel System

1. Connect the black hose of Pressure Tester (part of EFI Service Kit, see Section 2), to the test valve in the fuel rail. Route the clear hose into a portable gasoline container or the equipment fuel tank.

2. Turn on the key switch to activate the pump and check the system pressure on the gauge. If system pressure of 39 psi ± 3 is observed, the relay, fuel pump, and regulator are working properly. Turn the key switch off and depress the valve button on the tester to relieve the system pressure.

a. If the pressure is too high, and the regulator is

outside the tank (just down line from the pump), check that the return line from the regulator to the tank is not kinked or blocked. If the return line is good, replace the regulator (see ‘‘Regulator Service’’ on page 5B.21).

b. If the pressure is too low, install in-line ‘‘T’’

between the pump and regulator and retest the pressure at that point. If it is too low there also, replace the fuel pump.

3. If the pump did not activate (step 2), disconnect the plug from the fuel pump. Connect a DC voltmeter across the terminals in the plug, turn on the key switch and observe if a minimum of 7 volts is present. If voltage is between 7 and 14, turn key switch off and connect an ohmmeter between the terminals on the pump to check for continuity.

Fuel Pressure Regulator

Figure 5B-27. External Fuel Pressure Regulators with Base.

a. If there was no continuity between the pump

terminals, replace the fuel pump.

b. If the voltage was below 7, test the wiring

harness and relay as covered in the ‘‘Electrical Relay’’ section.

4. If voltage at the plug was good, and there was continuity across the pump terminals, reconnect the plug to the pump, making sure you have a good connection. Turn on the key switch and listen for the pump to activate.

a. If the pump starts, repeat steps 1 and 2 to

verify correct pressure.

b. If the pump still does not operate, replace it.

5B.20

Figure 5B-28. Internal Fuel Pressure Regulator.

General

The fuel pressure regulator assembly maintains the required operating system pressure of 39 psi ± 3. A rubber-fiber diaphragm (see Figure 5B-29) divides the regulator into two separate sections; the fuel chamber and the pressure regulating chamber. The pressure regulating spring presses against the valve holder (part of the diaphragm), pressing the valve against the valve seat. The combination of atmospheric pressure and regulating spring tension equals the desired operating pressure. Any time the fuel pressure against the bottom of the diaphragm exceeds the desired (top) pressure, the valve opens, relieving the excess pressure, returning the excess fuel back to the tank.

Pressure Regulating Spring

Section 5B

EFI Fuel System

Pressure Regulating Chamber

Diaphragm

Valve

Inlet Port

Return Port (to tank)

Figure 5B-29. Fuel Pressure Regulator Details.

Service

Depending on the application, the regulator may be located in the fuel tank along with the fuel pump, or outside the tank just down line from the pump. The regulator is a sealed, non-serviceable assembly. If it is faulty, it must be separated from the base/holder assembly and replaced as follows:

1. Shut engine off, make sure engine is cool, and disconnect the negative (-) battery cable.

2. Depressurize fuel system through test valve in fuel rail (see fuel warning on page 5B.2).

3. Access the regulator assembly as required and clean any dirt or foreign material away from the area.

Valve Seat

Fuel Chamber

Outlet Port (to fuel rail)

Figure 5B-30. External Regulators and Base/ Holders.

Figure 5B-31. Internal Regulator and Base/Holder.

4. External Regulator -

Based upon the style of regulator used (see Figure 5B-30):

a. Remove the two screws securing the

mounting bracket to the regulator housing. Remove the O-Ring and pull the regulator out of the housing.

b. Remove the snap ring and remove regulator

from base/holder.

Internal (In-Tank) Regulator -

Remove the three screws securing the retaining ring and regulator in the base/holder assembly. Grasp and pull the regulator out of the base/ holder. See Figure 5B-31.

5. Always use new O-Rings and hose clamps when installing a regulator. A new replacement regulator will have new O-Rings already installed. Lubricate the O-Rings (external regulator) with light grease or oil.

6. a. Install the new regulator by carefully pushing

and rotating it slightly into the base or housing.

b. External Regulators with Square Base

Housing Only; Install a new O-Ring between the regulator and the mounting bracket. Set the mounting bracket into position.

c. Secure the regulator in base with the original

retaining ring or screws. Be careful not to dent or damage the body of the regulator as operating performance can be affected.

7. Reassemble any parts removed in step 3.

5B.21

Section 5B EFI Fuel System

8. Reconnect the negative (-) battery cable.

9. Recheck regulated system pressure at fuel rail test valve.

Fuel Filter

EFI engines use a high-volume, high-pressure, 10-15 micron, in-line fuel filter.

Figure 5B-32. In-Line Fuel Filter.

General

The fuel rail is a formed tube assembly that feeds fuel to the top of the injectors. The tops of the injectors fit into formed cups in the fuel rail. When the rail is fastened to the manifold, the injectors are locked into place. A small retaining clip provides a secondary lock. Incorporated into the fuel rail is a pressure relief/ test valve for testing operating pressure or relieving fuel system pressure for servicing. The fuel supply line is attached to the barbed end of the fuel rail with an Oetiker hose clamp.

Service

The fuel rail is mounted to the throttle body/intake manifold. It can be detached by removing the two mounting screws and the injector retaining clips. Thoroughly clean the area around all joints prior to any disassembly. No specific servicing is required unless operating conditions indicate that it needs internal cleaning or replacement.

Fuel Line

Service

Fuel filter replacement is recommended every 1500 hours of operation or more frequently under

extremely dusty or dirty conditions. Use only the specified filter, and install it according to the directional arrows. Do not use a substitute filter as operating performance and safety can be affected. Relieve system pressure through the safety valve in the fuel rail before servicing.

Fuel Rail

TPS

Locking Clip

Figure 5B-33. Manifold Assembly .

Fuel Injector

Figure 5B-34. High Pressure Fuel Line.

General

Special low permeation high-pressure fuel line with an SAE30 R9 rating is required for safe and reliable operation, due to the higher operating pressure of the EFI system. If hose replacement is necessary, order Fuel Line Service Kit, Part No. 25 111 37-S (containing 60" of high-pressure hose and 10 Oetiker clamps), or use only the type specified. Special Oetiker clamps (Kohler Part No. 24 237 05-S) are used on all fuel line connections to prevent tampering and safety hazards with the high fuel pressure. The old clamp must be cut to open a connection, so replacement is necessary each time. Oetiker Clamp Pliers (part of EFI Service Kit, see Section 2) is used to crimp the replacement clamps.

5B.22

Section 5B

EFI Fuel System

CAUTION:

Fuel lines between the fuel pump and fuel rail must be made from SAE 30 R9 fuel line. Standard fuel line (SAE 30 R7) may only be used between the fuel tank and pump (5/16” ID) and for the return line from the pressure regulator to the tank (1/4” ID). All high-pressure fuel line connections must be secured with Oetiker Clamps (Kohler Part No. 24 237 05-S), installed/crimped with the corresponding pliers.

Throttle Body/Intake Manifold Assembly

Low Idle Speed Adjusting Screw

Throttle Body Intake Manifold

Fuel Rail

For starting and warm up, the ECU will adjust the fuel and ignition timing, based upon ambient temperature, engine temperature, and loads present. In cold conditions, the idle speed will probably be higher than normal for a few moments. Under other conditions, the idle speed may actually start lower than normal, but gradually increase to the established setting as operation continues. Do not attempt to circumvent this warm up period, or readjust the idle speed during this time. The engine must be completely warmed up for accurate idle speed adjustment.

Adjustment Procedure

1. Make sure there are no fault codes present in the ECU memory.

2. Start the engine and allow it to fully warm up and establish closed looped operation (approximately 5-10 min.).

3. Place the throttle control in the ‘‘idle/slow’’ position and check the idle speed with a tachometer. Turn the idle speed screw in or out as required to obtain 1500 RPM, or the idle speed specified by the equipment manufacturer.

Figure 5B-35. Upper Intake Manifold.

General

The EFI engines have no carburetor, so the throttle function (regulate incoming combustion airflow) is incorporated in the intake manifold assembly. The manifold consists of a one-piece aluminum casting which also provides mounting for the fuel injectors, throttle position sensor, fuel rail, air baffle, idle speed screw, and air cleaner assembly.

Service

The throttle body/intake manifold is serviced as an assembly, with the throttle shaft, throttle plates, and idle speed adjusting screw installed. The throttle shaft rotates on needle bearings (non-serviceable), capped with rubber seals to prevent air leaks.

Idle Speed Adjustment (RPM)

General

The idle speed is the only adjustment that may be performed on the EFI system. The standard idle speed setting for EFI engines is 1500 RPM, but certain applications might require a different setting. Check the equipment manufacturer’s recommendation.

4. The low idle speed adjustment can affect the high speed setting. Move the throttle control to the full throttle position and check the high speed. Adjust as necessary to 3750 RPM (no load), or the speed specified by the equipment manufacturer.

Idle Speed Screw Dampening Spring

A small dampening spring (Kohler Part No. 24 089 42-S) is attached to the end of the idle speed screw of some EFI engines to help stabilize no load operating speeds. See Figure 5B-36.

5B.23

Section 5B EFI Fuel System

Dampening Spring (Some Models)

Figure 5B-36. Idle Speed Screw Details.

The idle speed adjustment procedure remains the same for engines with or without a dampening spring. Typically, no periodic servicing is necessary in this area. If however, removal/replacement of the dampening spring is required, reinstall it as follows:

1-3 mm (0.039-0.117 in.) Exposed Length Off End Of Adjustment Screw

Idle Speed Screw

If the governor/throttle components are all intact, but you think there may be a problem with the adjustment, follow Procedure A to check the setting. If the governor lever was loosened or removed, go immediately to Procedure B to perform the initial adjustment.

A. Checking the Initial Adjustment

1. Unsnap the plastic linkage bushing attaching the throttle linkage to the governor lever. See Figure 5B-37. Unhook the damper spring from the lever, separate the linkage from the bushing, and remove the bushing from the lever. Mark the hole position and unhook the governor spring from the governor lever.

Throttle Linkage

Linkage Bushing

Damper Spring

1. Thread the spring onto the end of idle screw

leaving 1-3 mm (0.039-0.117 in.) of the spring extending beyond the end of the idle speed screw.

2. Secure spring onto the screw with a small amount of Permabond adhesive. Do not get any adhesive on free coils of spring.

3. Start the engine and recheck the idle speed settings, after sufficient warm up. Readjust as required.

™

LM-737 or equivalent Loctite

Initial Governor Adjustment

The initial governor adjustment is especially critical on EFI engines because of the accuracy and sensitivity of the electronic control system. Incorrect adjustment can result in overspeed, loss of power, lack of response, or inadequate load compensation. If you encounter any of these symptoms and suspect them to be related to the governor setting, the following should be used to check and/or adjust the governor and throttle linkage.

Figure 5B-37. Throttle Linkage/Governor Lever Connection.

2. Check if the engine has a high-speed throttle stop screw installed in the manifold casting boss. See Figure 5B-38.

High-Speed Throttle Stop Screw

Figure 5B-38. Throttle Details.

5B.24

Section 5B

EFI Fuel System

a. On engines without a stop screw, pivot the

throttle shaft and plate assembly into the “Full Throttle” position. Insert a 1.52 mm (0.060 in.) feeler gauge between the rear tang of the throttle shaft plate and the underside of the manifold boss. Use a locking pliers (needle nose works best) to temporarily clamp the parts in this position. See Figure 5B-39.

Feeler Gauge

Figure 5B-39. Inserting Feeler Gauge (Engines Without Stop Screw).

B. Setting the Initial Adjustment

1. Check the split where the clamping screw goes through the governor lever. See Figure 5B-41. There should be a gap of at least 1/32". If the tips are touching and there is no gap present, the lever should be replaced. If not already installed, position the governor lever on the cross shaft, but leave the clamping screw loose.

Figure 5B-41. Checking ‘‘Split’’ of Clamp.

b. On engines with a stop screw, pivot the

throttle shaft and plate into the “Full Throttle” position, so the tang of the throttle shaft plate is against the end of the high-speed stop screw. See Figure 5B-38. Temporarily clamp in this position.

3. Rotate the governor lever and shaft counterclockwise until it stops. Use only enough pressure to hold it in that position.

4. Check how the end of the throttle linkage aligns with the bushing hole in the governor lever. See Figure 5B-40. It should fall in the center of the hole. If it doesn’t, perform the adjustment procedure as follows.

2. Follow the instructions in Step 2 of ‘‘Checking the Initial Adjustment,’’ then reattach the throttle linkage to the governor lever with the bushing clip. It is not necessary to reattach the damper or governor springs at this time.

3. Insert a nail into the hole in the top of the cross shaft. Using light pressure, rotate the governor shaft counterclockwise as far as it will turn, then torque the hex nut on the clamping screw to

6.8 N·m (60 in. lb.). See Figure 5B-42. Make sure that the governor arm has not twisted up or down after the nut has been tightened.

Figure 5B-40. Throttle Link in Center of Hole.

Figure 5B-42. Adjusting Governor Shaft.

5B.25

Section 5B EFI Fuel System

4. Verify that the governor has been set correctly. With the linkage still retained in the “Full Throttle” position (Step 2), unsnap the bushing clip, separate the linkage from the bushing, and remove the bushing from the lever. Follow Steps 3 and 4 in ‘‘Checking the Initial Adjustment’’.

5. Reconnect the dampening spring into its governor lever hole from the bottom. Reinstall the bushing and reattach the throttle linkage. See Figure 5B-37. Reattach the governor spring in the marked hole.

6. Start the engine and allow it to fully warm up and establish closed loop operation (approximately 5-10 min.). Check the speed settings and adjust as necessary, first the low idle speed, and then the high speed setting.

Troubleshooting

General

When troubleshooting a problem on an engine with EFI, basic engine operating problems must be eliminated first before faulting the EFI system components. What appears to be an EFI problem could be something as simple as a fuel tank with debris in the bottom or a plugged vent. Be sure the engine is in good mechanical operating condition, and all other systems are functional before attempting to troubleshoot the EFI system.

Engine starts hard or fails to start when hot

1. Faulty spark plugs

2. Fuel pump not running

3. Fuel pressure low

4. Insufficient fuel delivery

5. TPS offset incorrect (Initialization)

6. Speed sensor loose or faulty

7. TPS faulty

8. Engine temperature sensor faulty

9. Faulty injectors

Engine stalls or idles roughly (cold or warm)

1. Faulty spark plugs

2. Insufficient fuel delivery

3. TPS offset incorrect

4. TPS faulty

5. Faulty engine temperature sensor

6. Faulty injectors

Engine misses, hesitates, or stalls under load

1. Fuel injector(s), fuel filter, fuel line, or fuel pickup dirty/restricted

2. Dirty air cleaner

3. Insufficient fuel pressure or fuel delivery

4. Vacuum (intake air) leak

5. Improper governor setting, adjustment or operation

6. Speed sensor malfunction

7. TPS faulty, mounting problem or "TPS Initialization Procedure" incorrect

8. Bad coil(s), spark plug(s), or wires

Troubleshooting Guide

Engine starts hard or fails to start when cold

1. Fuel pump not running

2. Faulty spark plugs

3. Old/stale fuel

4. Incorrect fuel pressure

5. Speed sensor loose or faulty

6. TPS offset incorrect (initialization)

7. TPS faulty

8. Engine temperature sensor faulty

9. Faulty coils

10. Low system voltage

11. Faulty injectors

5B.26

Low Power

1. Faulty/malfunctioning ignition system

2. Dirty air filter

3. Insufficient fuel delivery

4. Improper governor adjustment

5. Plugged/restricted exhaust

6. One injector not working

7. Basic engine problem exists

8. TPS faulty or mounting exists

9. Throttle plates in throttle body/intake manifold not fully opening to WOT stop (if so equipped)

Section 5B

EFI Fuel System

Electrical System

The EFI system is a 12 VDC negative ground system, designed to operate down to a minimum of 7.0 volts. If system voltage drops below this level, the operation of voltage sensitive components such as the ECU, fuel pump, and injectors will be intermittent or disrupted, causing erratic operation or hard starting. A fully charged, 12 volt battery with a minimum of 350 cold cranking amps is important in maintaining steady and reliable system operation. Battery condition and state of charge should always be checked first when troubleshooting an operational problem.

Keep in mind that EFI-related problems are more often caused by the wiring harness or connections than by the EFI components. Even small amounts of corrosion or oxidation on the terminals can interfere with the milliamp currents used in system operation. Cleaning the connectors and grounds will solve problems in many cases. In an emergency situation, simply disconnecting and reconnecting the connectors may clean up the contacts enough to restore operation, at least temporarily.

If a fault code indicates a problem with an electrical component, disconnect the ECU connector and test for continuity between the component connector terminals and the corresponding terminals in the ECU connector using an ohmmeter. Little or no resistance should be measured, indicating that the wiring of that particular circuit is OK. An illustrated listing of numerical terminal locations, for each style of ECU/ connector is provided on pages 5B.28, 5B.31, or 5B.32.

5B.28 for “35 Pin” (MA 1.7) Metal-Cased ECU 5B.31 for “24 Pin” (MSE 1.0) Plastic-Cased ECU 5B.32 for “32 Pin” (MSE 1.1) Plastic-Cased ECU

NOTE: When performing voltage or continuity tests,

avoid putting excessive pressure on or against the connector pins. Flat pin probes are recommended for testing to avoid spreading or bending the terminals.

5B.27

Section 5B EFI Fuel System

“35 Pin” (MA 1.7) Metal-Cased ECU Systems

Pin #

1 2 3 4 5 6 7 8

9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35

Component

Ignition Coil #1

Not used

Engine Speed Sensor

ECU Production Test Terminal

Not Used Not Used Not Used

TPS Initialization Terminal

Engine Ground

O2 Sensor Not Used

Throttle Position Sensor

Not Used

Oil Temperature Sensor

Not Used

ECU Permanent Battery Voltage

ECU Switched Battery Voltage

Engine Ground Ignition Coil #2 Vehicle Ground

Engine Speed Sensor

Not Used Not Used Not Used

Throttle Position Sensor

Not Used

Throttle Position Sensor/Oil Temperature Sensor

Power Relay

Not Used Not Used

Malfunction Indicator Light

Not Used

Vehicle Ground

Not Used

Fuel Injectors

19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

5B.28

“24 Pin” (MSE 1.0) Plastic-Cased ECU Systems

Section 5B

EFI Fuel System

Pin #

1 2 3 4 5 6 7 8

9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Function

Permanent Battery Voltage Switched Ignition Voltage Safety Switch Throttle Position Sensor (TPS) and Temperature Sensor Ground

Not Used

Oil Temperature Sensor Input

Not Used Throttle Position Sensor (TPS) Input Speed Sensor Input Speed Sensor Ground Oxygen Sensor Input

Not Used (Oxygen Sensor Ground if needed) Diagnostic Line Throttle Position Supply Voltage Battery Ground Injector 1 Output Injector 2 Output Main Relay Output Malfunction Indicator Light (MIL)

Not Used (Tach Output if needed)

Not Used Ignition Coil #1 Output Ignition Coil #2 Output TPS Initialization Terminal

10 11

1 2

3 4 5

6 7

8 9

13 14 15

16 17

18 19 20

21 22

23 24

5B.31

Kohler CH20, CH18-750, CH750, CH740, CH23 User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual

Contents