Onan RDJE, RDJEA Service Manual

Service

Diesel

Engines

974-0250

(SPEC

A)

10-88

Printed

in

U.S.A

Safety

Precautions

It is recommended that you read your engine manual and
become thoroughly acquainted with your equipment be-

fore you start the engine.

WARNING

This symbolls

used

throughout this

a

manual

to

warn of possible serlous

personal injury.

Thls symbol refers

to

possible equip-

ment damage.

Fuels, electrical equipment, batteries, exhaust gases and
moving parts present potential hazards that could result in
serious, personal injury. Take care in following these
recommended procedures.

Safety Codes

0

All local, state and federal codes should be consulted
and complied with.

0

This engine is not designed or intended for use in
aircraft. Any such use is at the owner's sole risk.

General

0

Provide appropriate fire extinguishers and install them

.

in convenient locations. Use an extinguisher rated ABC
by NFPA.

0

Make sure that all fasteners on the engine are secure
and accurately torqued. Keep guards in position over

fans, driving belts, etc.

If it is necessary to make adjustments while the engine

is

running, use extreme caution when close to hot ex-

hausts, moving parts, etc.

.

Protect Against Moving Parts

0

Do not wear loose clothing in the vicinity of moving
parts, such as PTO shafts, flywheels, blowers, coup­lings, fans, belts, etc.

0

Keep your hands away from moving parts.

Batteries

0

Before starting work on the engine, disconnect batter­ies

to

prevent inadvertent starting of the engine.

0

DO

NOT

SMOKE while servicing batteries, Lead acid
batteries give off a highly explosive hydrogen gas which
can be ignited by flame, electrical arcing or by smoking.

0

Verify battery polarity before connecting battery cables.
Connect negative cable last.

Fuel System

0

DO

NOT

fill fuel tanks while engine is running.

DO

NOT smoke or use an open flame in the vicinity of
the engine or fuel tank. Internal combustion engine
fuels are highly flammable.

Fuel lines must be of steel piping, adequately secured,
and free from leaks. Piping at the engine should be
approved flexible line. Do not use copper piping for
flexible lines as copper will work harden and become
brittle enough to break.

Be sure all fuel supplies have a positive shutoff valve.

.I

Exhaust System

Exhaust products

of

any internal combustion engine

are toxic andcan cause injury, or death if inhaled.

All

engine applications, especially those within a confined
area, should be equipped with an exhaust system to
discharge gases to the outside atmosphere.

Do not use exhaust gases to heat a compartment.

0

Make sure that your exhaust system is free of leaks.
Ensure that exhaust manifolds are secure and are not
warped by bolts unevenly torqued.

Exhaust Gas

is

Deadly!

Exhaust gases contain carbon monoxide, a poisonous gas
that might cause unconsciousness and death. It is an
odorless and colorless gas formed during combustion of
hydrocarbon fuels. Symptoms of carbon monoxide poi­soning are:

0

Dizziness Vomiting

0

Headache Muscular Twitching

Weakness and Sleepiness

If

you experience any of these symptoms, get out into fresh
air immediately, shut down the unit and do not use until it
has been inspected.

The best protection against carbon monoxide inhalation is

proper installation and regular, frequent inspections

of

the
complete exhaust system. If you notice a change in the
sound or appearance of exhaust system, shut the unit down

immediately and have

it

inspected and repaired at once bya

competent mechanic.

'Cooling System

0

Coolants under pressure have a higher boiling point
than water. DO NOT open a radiator pressure cap when
coolant temperature

is

above

212°F

(lOO°C) or while

engine is running.

Throbbing in Temples

Keep the Unit and Surrounding Area Clean

Make sure that oily rags are not left on or near the
engine.

Remove all unnecessary grease and oil from the unit.

Accumulated grease and

oil

can cause overheating and
subsequent engine damage and present a potential fire
hazard.

E-4

*

TABLE

OF

CONTENTS

PART I SERVICE MANUAL

Specifications

.....................................................

2

Dimensions and Clearances

........................................

3

Assembly Torques and Special Tools

................................

5

Engine Troubleshooting

............................................

6

Service and Maintenance

..................................

;

........

7

Exhaust System

..................................................

11

Cooling System

...................................................

13

Fuel

System

......................................................

16

Governor System

.................................................

33

Starting System

..................................................

35

Engine Disassembly

..............................................

42

Control

System

...................................................

54

Oilsystem

.......................................................

30

TO

AVOID POSSIBLE PERSONAL INJURY OR

VICE REPRESENTATIVE MUST PERFORM ALL

S

E R VICE

.

EQUIPMENT DAMAGE. AN AUTHORIZED SER-

1

SPEClFl

CATIONS

RDJEIRDJEA

Dimensions (inches)

Height

...........................................................................

28.71 (729.2

mm)

Width

............................................................................

19.75 (501.6

mm)

Length..

.........................................................................

23.04 (585.2

mm)

.............................................................................

307

Ib.

Weight

2

Number of Cylinders (in-line)

.......................................................

Displacement (cu in.)

.............................................................

70

inch3

(1.2

litre)

Bore

3.5 (88.96

mm)

Stroke

3.625 (92.08

mm)

yes

Oil Control..

....................................................................................

1

Stellite Faced Valves..

...........................................................................

yes

Stellite Replaceable Valve Seats

..................................................................

Yes

Valve Rotator..

...................................................................................

Yes

Governor (internal flyball type-externally adjustable)

.............................................

Yes

Governor Regulation (percent)

.....................................................................

5

Nominal Battery Voltage

...........................................................................

12

SAE Group

lH,

6

volt..

........................................................................

two

Amp/Hr SAE

20

hr (minimum).

........................................................

120 (432

kC)

.

Solenoid Shift Starter. yes

Injection Pump (American Bosch type)

..........................................................

PSU

..............................................................................

1-2

Primary and Secondary Fuel Filters..

.............................................................

Yes

Fuel Pump Lift (feet)..

....................................................................

6 (1.8

m)

Oil Pump (gear type)

............................................................................

yes

Oil

Filter (full flow)

...............................................................................

yes

Oil Capacity

U.S.

quarts (includes Filter).

................................................

3 (2.84

litre)

Exhaust Connections (pipe tapped).

..................................................

1-1/2 (38.1

mm)

Shaft Length

.........................................................................

4

(101.6

mm)

Keyway Length..

......................................................................

3 (76.2

mm)

Keyway Width..

.....................................................................

3/8 (9.53

mm)

Keyway Depth..

....................................................................

3/16 (4.76

mm)

Compression Ratio

.......................................................................

i

....

19.O:l.O

.................................................................................

.............................................................................

Main Bearings are Leaded Bronze, Precision Type for Replacement (qty.)

............................

2-

Compression..

..................................................................................

3

Connecting Rod Bearings Tri-metal Replaceable

..................................................

Piston Rings (chrome plated)

Battery Size

...........................................................................

Injection Order

Power Take-off (inches)

Shaft Diameter

....................................................................

1-314. (44.5

mm)

NOTE:

The RDJE and RDJEA are almost identical engines, the differences being that the RDJE is an even firing engine; both

pistons move up and down together. The RDJEA is an odd firing engine; one piston moves up while the other moves down.

For

the

above reasons, the crankshafts, injection pumps, camshafts, and associated piece parts are different.

2

DIMENSIONS

AND

CLEARANCES

RDJWRDJEA

All

clearances given at room temperature

of

70°F (21°C)

.

All dimensions in inches (millimetres in parentheses) unless otherwise specified .

d

.

CAMSHAFT

Bearing Journal Diameter. Front

.......................................

2.500-2.505 (63.500-63.627)

Bearing Journal Diameter. Rear

..................................

1.1875-1.1880 (30.1625-30.1752)

Bearing Clearance Limit

...........................................

0.0015-0.0030 (0.0381-0.0762)

End Play

.............................................................

0.007-0.039 (0.1778-0.9906)

Cam Tappet Diameter

.............................................

0.875-0.873 (22.161 5-22.1742)

Cam Tappet Hole Diameter

......................................

0.8755-0.8765 (22.2377-22.2631)

Large Bore Diameter

.............................................

2.1871-2.1876 (55.5523-55.5650)

Small Bore Diameter

.................................................

1.044-1.045 (26.51 76-26.543)

(Center-to-Center)

.............................................

5.998-6.002 (152.3492-152.4508)

Clearance, Bearing to Crankshaft

......................................

0.001-0.003 (0.0254-0.0762)

Bore Honed Diameter

..............................................

3.4995-3.5005 (88.8873-88.91 27)

Maximum Allowable Taper

..............................................................

0.005

(0.127)

Maximum Allowable Out-Of-Round

......................................................

0.001 (0.025)

Main Bearing Journal Diameter

.....................................

2.2437-2.4450 (56.989-62.103)

Main Bearing Clearance

.............................................

0.0030-0.0043 (0.076-0.109)

Connecting Rod Journal Diameter

................................

2.0597-2.0605 (52.3240-52.3367)-

Rod

Bearing Clearance

............................................

0.0019-0.0038 (0.0482-0.0965)

End Play

...............................................................

0.010-0.015 (0.254-0.381)

CONNECTING RODS

Large Bearing Bore to Small Bearing Bore

CYLINDER

CRANKSHAFT

PISTONS AND RINGS

Clearance

in

Cylinder

Measure 90" to pin. just below oil ring

...............................

0.0055-0.0075 (0.1397-0.1905)

Ring Groove Width

TOP

..........................................................

0.0970-0.0980 (2.464-2.489)

NO

2

.........................................................

0.0965-0.0975 (2.451-2.477)

NO

3

.........................................................

0.0965-0.0975 (2.451 -2.477)

NO

4

.........................................................

0.1880-0.1897 (4.775-4.81 8)

Wid th-All Rings

..................................................

0.0925-0.0935 (2.3495-2.3749)

Clearance

in

Piston

................................................................

Thumb Push Fit

Connecting Rod Bushing Clearance

................................

0.0002-0.0007 (0.0050-0.0178)

..............................................................

Ring Gap 0.010-0.020 (0.254-0.508)

PISTON PIN

STARTING

MOTOR

(Prestolite)

........................................................................

Rotation Counterclockwise
Pinion Clearance to Pinion Stop (Solenoid Plunger Bottomed)

..............

0.070-0.120 (1.78-3.05)

Pinion Rest Position-Distance from Pinion Housing

Mounting Face to Outer Edge

of

Pinion

...........................

1-9/32 - 1-15/64 (32.54-37.31)

Armature End Play

......................................................

0.005-0.030 (0.030-0.760)

Stem Diameter

....................................................

0.3405-0.3415 (8.6487-8.6741)

Guide Clearance

..................................................

0.0015-0.0030 (0.0381-0.0762)

Valve Face

........................................................

:

............................

42"

VALVE-INTAKE

...........................................................................

Clearance 0.017 (0.4318)

3

VALVE-EXHAUST

Stem Diameter

....................................................

0.3405-0.3415 (8.6487-8.6741)

Guide Clearance

..................................................

0.0025-0.0045 (0.0635-0.1143)

Valve Face

....................................................................................

45'

Clearance

...........................................................................

0.017 (0.4318)

Length

............................................................................

1.7812 (45.2424)

Outside Diameter

.................................................

0.469-0.4696 (11.9126-11.9253)

Exhaust

......................................................

0,344-0.345 (8.7376-8.7630)

Intake ........................................................

0.342-0.343 (8.6868-8.7122)

Cylinder Block Bore Diameter

......................................

0.467-0.468 (11.8618-11.8872)

Bore Diameter

intake

........................................................

1.361-1.362 (34.570-34.595)

Exhaust

.......................................................

1.364-1.365 (34.646-34.671)

Depth (from cylinder head face)

....................................

0.433-0.439 (10.9982-1 1.1506)

I

nsert-Outside Diameter

..........................................

1.364-1.365 (34.6456-34.671

0)

Seat Width

........................................................

0.0469-0.0625 (1.1912-1.5875)

Angle

.........................................................................................

45'

Available Oversizes

..................................................................

0.002 (0.0508)

VALVE

GUIDE

Inside Diameter (after reaming)

VALVE SEATS

0.005

(0.127)

0.010 (0.254)

0.025

(0.635)

VALVE

SPRINGS

.

*

Load-Valve Open

.......................................................

-87-97

Ibs

(12.0-13.4

N*)

Load-Valve Closed

.......................................................

45-49

ibs

(6.2-6.8

N')

N

.

Base unit . Newtons . Unit

of

force

.

4

ASSEMBLY

TORQUES

AND

SPECIAL

TOOLS

The assembly torques given here will assure proper
tightness without danger of stripping threads. If a
torque wrench

is

not available, estimate thedegree of
tightness necessary for the stud, nut, or screw. Be
careful not to strip threads. Use reasonableforceonly
and a wrench of normal length.

Specially designed place bolts do not require a

lockwasher or gasket.

Do

not attempt to use a

lockwasher with these bolts;

it

will defeat their

purpose. Check all studs, nuts and screws often, and

tighten as needed to keep them from working loose.

SPECIAL

TOOLS

These tools are available from Onan to aid service and
repair work.
Crankshaft gear pulling ring.

.............

.420-0275

Diesel nozzle tester

.....................

.420-0184

Diesel pintle nozzle cleaning tool set

(includes injection nozzle centering
tool)

..................................

420-0208

Driver, Valve seat

.......................

.420-0270

Oil seal guide and driver..

...............

.420-0456

Nozzle centering sleeve

.................

.420-0321

Diesel nozzle tester

.....................

.420-0322

Combination main and cam

bearing driver

........................

.420-0326

Diesel compression tester

...............

.420-0283

Valve spring compressor tool

............

.420-0210

Valve seat remover..

....................

.420-0311

Flywheel puller

.........................

.420-0100

TORQUE

SPECIFICATIONS

F1.-Lb.

Nom

Connecting rod bolt

............

27-29 (37-39)

Rocker-Box cover

..............

8-10

(1

1-14)

Cylinder head bolt.

.............

44-46 (60-62)

Exhaust manifold nuts

..........

13-15* (18-20)

Flywheel mounting screw

.......

65-70 (88-95)

Fuel pump mounting screws

....

15-20 (20-27)

Gear case cover

................

15-20 (20-27)

Injection nozzle mounting

Injection pump mounting

screws

.......................

15-16 (20-22)

Intake manifold..

...............

13-15

(1

8-20)

Oil base mounting screws..

.....

45-50 (61-68)

Oil Filter

..........

Hand tight plus

1/4

to

1/2

turn

Oil pump mounting screws..

....

15-20 (20-27)

Rear bearing plate.

.............

40-45 (54-61)

Glow plug..

....................

10-15 (18-20)

screws

.......................

20-21 (27-28)

Rocker arm nut..

...............

4-lo** (5-13)

Rocker arm stud..

..............

55-60 (75-81)

-

Exhaust nuts must be tightened evenly.

**

-

This torque

is

due

to

friction between the threads
only and locks the nuts in place. Use the rocker
arm nut to adjust valve lash.

5

ENGINE

TROUBLESHOOTING

6

SERVICE

AND

MAINTENANCE

PR

E-STARTI

N

G

Preparations for the initial and each additional star­ting operation should include careful checks of the
oil, fuel, cooling, and electrical systems. The cylinder
air housing door should be closed with all airshrouds

in

place.

Before engine is put in operation, check all com-

ponents for mechanical security. If an abnormal
condition, defective part, or operating difficulty is
detected, repair or service as required. The engine
should be kept free of dust,

dirt,

and spilledoil or fuel.

Be sure proper operating procedure is followed.

Crankcase

Oil:

Use an oil with the API designation

CD/SD or CD/SE. However, to reduce oil consump­tion to a normal level in theshortest time possible on a

new or rebuilt engine, use CC oil for the first fill only

(50

hours). Then use the recommended oil only.
Select the correct SAE grade oil by referring to the
following:

Above

32"

F

(0"

C)

.......................

SAE

30

0"

F

to

32" F

(-18" C to 0°C)

...

SAE 1OW or

5W-30

Below

0"

F

(-18"

C)

..................

SAE

5W-30

Multigrade oils are recommended for temperatures of

32"

F

(0"

C) and below, but they are not recommend-

ed for temperatures above

32"

F

(0"

C). When adding

oil between oil changes,

it

is preferable to use the
same brand as various brands of oil may not be
compatible when mixed together.

Never remove

011

level Indicator cap with the

engine running, because oil will blow out of

the tube causing possible injury.

Recommended Fuel:

Although number 2 diesel fuel
gives the best economy for most operating con­ditions, number

1

diesel fuel can be used:

1.

When ambient temperatures are below

32°F

2.

During long periods of light engine load;

or,

3.

If preferred by user.

(0"

C);

Use low sulfur content fuel having a pour point (ability
to filter) of at least 10" below the lowest expected
temperature. Keep the fuel clean and protected from

adverse weather. Leave some room for expansion

when filling the fuel tank.

Due to the precise tolerances of diesel injec-

tion systems, it is extremely important the fuel
be kept clean. Dirt in the system can cause severe damage to both
the injection pump and the injection nozzles.

Bleed air from fuel system as follows: Disconnect the
fuel return line. See Figure 1

.

Operate the hand

priming lever on diaphragm type fuel transfer pump
until there are no air bubbles in fuel flowing from the

fuel return line fitting. Then connect the fuel return

line.

'WORK

TRANSFER PUMP

PRIMING LEVER UNTIL

FUEL

FLOWS FROM

RETURN

LINE

FITTING

OF

INlECTlON PUMP.

FIGURE

1.

BLEED FUEL SYSTEM

If

the camshaft pump lobe is up, crank engine one revolution to

permit hand priming. When finished, return priming lever inward

(disengaged position) to permit normal pump operation.

7

PRE-HEATING AND STARTING

Extremes

in

starting temperatures may require ad­ditional preheating. If engine fails to startquickly, rest
engine several seconds and repeat starting sequence.

CAUTION

If

engine does not start on first attempt, check

fuel system. Limit pre-heating to one minute

periods: longer periods can ruin the heater elements.

.1.

2.

3.

4.

For cold engine starting below

55"

F

(13" C),
depress manifold heater switch for one minute
only.

Push START-STOP switch to its START position.
Release switches after engine starts and reaches

speed.
Oil pressure should read at least 20 psi (pressure

relief valve is not adjustable).

On "standard" model, depress preheat switch for one minute and
then push start switch. Both switches must beengaged forstarting.

Do not apply overvoltage to the starting

circuit at any time. Overvoltage will destroy

the glow plugs and air heater in

2

to 3 seconds.

If

it becomes

necessary to use an additional source of power to start the set

-

use a

12

volt battery connected in parallel.

AUTOMATIC STARTING AND STOPPING

Optional controls may be used for automatic start and
stop, but must provide engine preheating.

The automatic control should have a time delay relay
to preheat glow plugs and the manifold heater for
about 20 seconds before cranking occurs. The time
delay relay prevents immediate engagement of the
starter in case the load is reapplied before the engine
stops.

STOPPING

1. Push fuel solenoid switch to

stop

position.

2.

Release switch when set stops. If stop circuit fails,
close fuel valve.

APPLYING LOAD

If

practicable, allow engine to warm up before
connecting a heavy load. Continuous overloading
causes high operating temperatures that can damage
the engine. The exhaust system may form carbon
deposits during operation at light loads; apply full
load occasionally before shut-down to prevent ex­cessive carbon accumulations.

Try to connect the load in steps instead of full load at
one time.

EXERCISE

Infrequent use results in hard starting. Operate at

least

30

minutes each week. Run longer if battery

needs charging.

BREAK-IN PROCEDURE

The unit should be run in the following sequence:

1. One half hour at 1/2 load.

2.

One half hour at

3/4

load.

3. Full load.

Continuous running under one half load during the

first few hundred hours usually results in poor piston

ring seating, causing higher than normal oil con-

sumption and blowby.

Drain and replace the crankcaseoil afterfirat

50

hounof operation;

drain while the englne Is stlll hot.

INSPECTION

Check for alignment of engine and load. Misalign­ment will cause excessivevibration and bearing wear.
Make a visual inspection of the entire installation.

VENTILATION

Good ventilation is needed to cool the engine and to
support combustion. Avoid recirculation of ven­tilating air. See

SPEClFlCATlONS

for air flow re-

quirements and vent sizes.

Utilizing exhaust heat to warm a room or

compartment occupied by people is not

recommended due to possible leakage of exhaust gases.

EXHAUST GASES ARE DEADLY

71

POISONOUS!

EXHAUST

Pipe exhaust gas outside any enclosure - exhaust gas

is poisonous. Exhaust pipes must not terminate near

inlet vents. Avoid sharp bends. Use sweeping, large-

radius elbows. Use a section of seamless, flexible
tubing between the engine and any rigid pipe to

restrict vibration. Increase exhaust pipe one size for
each additional

10

feet (304.8 cm) in length.

BATTERIES

Check the condition of the starting batteries at least
every two weeks. See that connections are clean and
tight. A light coating of non-conductive grease will
retard corrosion at terminals. Keep the electrolyte at
the proper level above the plates by adding distilled
water. Check specific gravity; recharge if below 1.280.

DUST AND DIRT

1. Keep radiator free of dirt, etc.

2. Service air cleaner as frequently as necessary.

3. Change crankcase oil every

50

operating hours.

4. Keep

oil

and fuel in dust-tight containers.

5.

Keep governor linkage clean.

HIGH ALTITUDE

Maximum power will be reduced approximately

4

percent for each

1000

feet (310 m) above sea level,

after the first

1000

feet (310 m).

8

LOW

TEMPERATURES

1.

Use correct SAE

No.

oil for temperature con­ditions. Change oil only when engine is warm. If
an unexpected temperature drop causes an
emergency, move engine to a warm location or
apply heated air (never use open flame) external-

ly

until oil flows freely.

2.

Use fresh fuel. Protect against moisture conden­sation.

3. Keep fuel system clean, and batteries

in

a well

charged condition.

4.

Partically restrict cool air flow but use care to

avoid overheating.

5.

Use additional preheat cycles during cold starts.

.Do not exceed one minute preheat

!cz3

periods; longer periods can

ruin

the

heater elements.

CAU~l~~

in dusty

conditions)

100

200

500

600

OUT-OF-SERVICE PROTECTION

The natural lubricating qualities of No. 2 diesel fuel

should protect a diesel engine for at least 30-days
when unit is not

in

service.

To

protect an engine that
will be out of service for more than 30 days, proceed
as follows:

1. Run engine until thoroughly warm; under at least

50

percent load.

2.

Shut down engine and drain oil base while still
warm. Refill and attach a warning tag indicating
viscosity of

oil

used.

3. Remove glow plugs. Pour 1-ounce of rust

in-

hibitor (or SAE #10 oil) into each cylinder. Install

Crank engine by hand only

to

distribute

m

oil in cylinder. Starter cranking is too
fast: oil or inhibitor fluid will fire if cranked with starter at
normal room temperature.

glow plugs.

CAUTION

Check air cleaner.

Clean governor linkage,
Change crankcase oil
Drain fuel condensation traps

in lines and filters,

see Note

1

Clean crankcase breather
Replace oil filter
Check battery condition

Check.start-disconnect circuit
Check valve clearances

Change primary filter

4.

Service air cleaner per

Maintenance

Schedule.

5.

Clean throttle and governor linkage and protect

6.

Plug exhaust outlets to prevent entrance of

7.

Clean and wipe entire unit. Coat parts susceptible

8.

Disconnect battery and follow standard battery

by wrapping with a clean cloth.
moisture, bugs, dirt, etc.
to rust with a light coat of grease or oil.

storage procedure.

3000

I

5000

Returning

a

Unit

to

Service.

1.

Remove cover and all protective wrapping.

Remove plug from exhaust outlet.

2.

Check warning tag on oil base and vertify that oil
viscosity is still correct for existing ambient
temperature.

3. Clean and check battery. Measure specificgravity

(1.260

at

77"

F

[25"

C]) and verify level is at split

ring. If specific gravity is low, charge until correct

value is obtained. If level is low, add distilled water

and charge until specific gravity is correct. DO
NOT OVERCHARGE.

Change secondary fuel filter
General overhaul (if required)

see Note

3

Do not smoke while servicing batteries.
Explosive gases are emitted from

batteries

in

opeation. Ignition

of

these gases can causesevere

personal injury.

4.

Check that fuel injectors and fuel lines are secure,
correctly torqued.

5.

Clean radiator.

6.

Connect batteries.

7.

Verify that no loads are connected to engine.

8.

Start engine.

After engine has started, excessive blue smoke will be
exhausted until the rust inhibitor or oil has burned away.

Before commencing any maintenance work

on the engine, controls, or associated equlp-

ment, disconnect batteries. Failure to do

so

could result

in

damage,

serious personal injury

In

the event

of

inadvertent starting.

OPERATOR AND SERVICE MAINTENANCE SCHEDULE

I

HOURSOF

I I

I

I

OPERATION MAINTENANCE TASK

I

Inspect exhaust system
Inspect engine
Check fuel

SUPDIV,

see Note

1

I

Check oil leve1:See Figure

2.

50

(more often

I

I

2000

Grind valves (if required)
Clean holes in rocker box
oil line and orifices

Check nozzle spray pattern,
see Note

2

NOTE

1.

Water or foreign material in fuel can ruin the injection
system. If daily inspection shows water or excessive dirt

in sediment bowl fuel, handling and storing facilities
should be checked and situation corrected. Primary and
secondary fuel filters must be replaced following correc­tion of fuel contamination problem.

2.

This service must be conducted by trained diesel

injection equipment personnel with suitable test
facilities. Omit this service

until

these conditions can be

met.

3.

Tighten head bolts and adjust valve clearance after first
50

hours on an overhauled engine.

9

OIL DRAIN EXTENSION

For service convenience, install a short (less than

10

inches [254 mm]) oil drain extension made from

standard pipe and fittings in the 1/2-inch (12.70

mm)

pipe-tapped oil drain hole in the base.

FUEL FILTER

FllEL PUMP

BALL JOINT

BREATHER

\%

HOSE

CAP AND VALVE

BREATHER TUBE

RDJE BREATHER TUBE

AMP'

OIL FILTER CHANGE

Place pan under old filter and remove by turning
counterclockwise. Clean filter mounting area.

Lubricate gasket on new filter with oil and screw filter
on clockwise until gasket touches mounting base,
then tighten

1/2

turn.

Never remove

011

level Indicator cap with the

engine running, because oil will blow out

of

the tube causing possible Injury.

OIL LEVEL INDICATOR

INLET OUTLET

ONDARY

FILTER

FILTER

DUAL

FUEL

FILTER SYSTEM

TO BREATHERJ TUBE

L.2.

RDJEA BREATHER PiPE

FIGURE

2.

MAINTENANCE PROCEDURES

10

GENERAL

The exhaust system must efficiently expel all engine
combustion products and muffle exhaust noises with

minimum back pressure. If back pressure is too high,
the volumetric efficiency of the engine is reduced,
fuel economy drops, exhaust temperature increases,

end valve life is shortened.

Back pressure must not exceed

27

inches

(686

mm)
of water column for the rated load when measured
with a manometerat

the

exhaust manifold, Figure

3.

FIGURE

3.

BACK PRESSURE TEST

WITH

MANOMETER

Exhaust

Smoke

A light gray or light blue smoke is a result of low

ambient temperature and light load. This smoke is
unburned fuel (not harmful to the engine) and
disappears when more load is applied.

Black smoke indicates overfueling (more fuel than
oxygen) and is usually caused by overloading. The
smoke or unburned fuel becomes carbon when raised

to a high temperature. Carbon contributes to engine

damage because it sticks to rings and fuel injection
nozzles.

EXHAUST GASES ARE DEADLY

-1

POISONOUS!

Vent exhaust gases outside. Use flexible tubing only
between the engine exhaust outlet and rigid piping.

WARN~NG

On service calls, always inspect exhaust

=

systems for possible leaks. Report any ex-

haust hazards to theowner/operatorand warn them

of

the potential

dangers to life

if

not repaired.

INSTALLATION

TIPS

Points to remember when installing an exhaust
system are:

Exhaust pipes should be as short as possible with
a minimum of fittings.
The muffler must be as close to the engine as
possible. Mufflers which are too far from the
manifold remain cool and collect carbon residue.

Pitch exhaust pipe upward from exhaust outlets

to avoid entrapment of rawdiesel fumes in muffler
at shutdown.

Avoid sharp bends by using large radius elbow.
Check back pressure with a mercury or water

column type manometer.

Position the exhaust outlet away from the engine

air intake.

Exhaust noise can be suppressed or reduced by:

Using a heavy duty exhaust system with a more
efficient muffler.
Avoiding use of flexible lines.

Installing a deflector at the exhaust outlet to

direct exhaust toward the ground, but away from

the operator.

Using a resonator in addition to a muffler.

The importance

of

exhaust systems (normally
supplied by the customer) cannot be over­emphasized. A poor or clogged system causes low

power, overheating and engine damage.

A

poor

exhaust system increases back pressure which

reduces efficiency.

If

the manufacturer tailon his own exhaust

system, an Onan applications engineer must

approve the installation for warranty purposes.

11

SINGLE THIMBLE DIAMETER

12”

(30s

mm)

LARGER

OR

DOUBLE VENTILATED THIMBLE

DIAMETER

6”

(

152

mm)

LARGER

INDOOR INSTALLATIONS

Locate exhaust outlet far from air inlet to avoid
recirculation. The engine exhaust is tapped for

1-1/2
inch thread. Use flexible tubing to connect theengine
exhaust to rigid pipe or muffler. Shield the line

if

it

passes through a combustible wall (Figure

4).

If turns

are necessary, use sweeping (large radius) elbows. If

pitched upward, install a condensation trap at point of
rise, Figure

5.

THANEXHAUS?

LINE

S

IN END

SLEEVE

EXHAUST LINE PASSING THROUGH

II

WALL OR PARTITION

FIGURE

4.

EXHAUST SHIELD

IF

EXHAUST LINE MUST BE PITCHED

UPWARD CONSTRUCT A TRAP OF PIPE

,.

FITTINGS AT POINT

OF

RISE

DRAIN CONDENSATION TRAP

PERIODICALLY

A617

FIGURE

5.

CONDENSATION TRAP

\WARNING)

ENGINE EXHAUST GAS (CARBON MONOXIDE) IS DEADLY!

Carbon monoxide is an odorless, colorless gas formed by incomplete
combustion of hydrocarbon fuels. Carbon monoxide is a dangerous gas that
can cause unconsciousness and is potentially lethal. Some of the symptoms or
signs of carbon monoxide inhalation are:

Dizziness Vomiting
Intense Headache
Weakness and Sleepiness

..

Muscular Twitching

Throbbing

in

Temples

If

you experience any of the above symptoms, get out into fresh air

immediately.
The best protection against carbon monoxide inhalation is a regular inspection

of the complete exhaust system.

If

you notice a change

in

the sound

or

appearance

of

exhaust system, shut the unit down immediately and have it

inspected and repaired at once by a competent mechanic.

12

COOLING

SYSTEM

RADIATOR

COOLED

SYSTEM

On radiator cooled models (Figure 6), the water pump
draws cooled water from the radiator through the
bottom hose and forces it into the cylinder water

jacket at the front of the engine. The water circulates

through the cylinder water jacket up through the
eylinder heads into the thermostat and flows through
the outlet hose into the top of the radiator. It circulates
down through the radiator while the fan blows cooling
air across the radiator. The water is drawn from the
bottom of the radiator by the pump to be recirculated.

WATER PUMP

--

WATER

FLOW,

ENGINE COOLING

c/"L

AIR

FLOW,

ENGINE VENTILATION

LEGEND

FIGURE

6.

RADIATOR

COOLING SYSTEM

During engine warmup, when the thermostat is
closed, the water bypasses the radiator.

It

flows
through a bypass line from the wateroutlet housing to
the pump and recirculates through the engine, until

PUGLEY

HOUSING GASKET

FIGURE 7a. WATER PUMP-EXPLODED VIEW

the water reaches normal operating temperature.

Recirculation ensures both rapid and even temper­ature increase of all engine parts during warmup.
Figure 7a shows an exploded view of the water pump.

Ventilation for radiator cooled models requires an
inlet opening for fresh air and an outlet opening for
heated air to prevent recirculation of heated air. The
openings should be at least the size of the radiator.

An expansion area in the closed cooling
system maintains proper coolant level by

preventing overflow and

loss

of

coolant when engine heats

up.

The engine water pump is a centrifugal type with a
cast impeller.

It

mounts on the front of the engine
cylinder block and is driven by the fan belt from the
crankshaft pulley. The inlet to the water pump isfrom
the radiator lower hose. The outlet is through the
water pump housing into the cylinder water jacket

passages.

The water pump requires no lubrication; the bearings

are permanently sealed and packed with a life time
lubricant. It requires no maintenance other than
bearing replacement if they show excessive
looseness, or replacement of the seal (impeller) if the
pump leaks water.

ANTI-FREEZE AND PRESSURE CAPS

Corrosion can shorten an engine's

life

by plugging up
radiator. cores, building up around hot spots near the
exhaust valves, and settling in low areas of the block.
The corrosive sediment insulates against proper heat

transfer and holds heat in. Most of the metals used

in
cooling systems are susceptible to corrosion damage
that causes coolant leaks and the temperature to rise
above safe, normal limits. Since pressurized cooling
systems run far hotter than the boiling point of water

(212°F [lOO"C]) at atmospheric pressure, even

greater breakdown

of

anti-freeze and water solutions

result. The average pressure cap

(15

pound

[103.5 kPa]) raises the boiling point of the engine

coolant to 265OF (132"

C).

Most anti-freeze manufacturers recommend

a

minimum 50-50 mixof ethyleneglycol anti-freezeand
water for winter and summer in closed water systems
with a complete change every year to avoid corrosion
and more expensive damage.

Defective pressure caps cause many cooling

problems and should be replaced every two years

or

whenever they malfunction.

13

COOLING SYSTEM MAINTENANCE

The cooling system including the block and radiator
should be cleaned and flushed at least once a year.
This is especially true in cold weather conditions or
when preparing unit for extended storage (over

30

days or more)!
The cooling system can work efficiently only when it is

clean. Scale and rust in the cooling system slow down
heat absorption and restrict water flow.

The thermostat is calibrated to open at 15OoFf2OF. It
should be checked also.

An appropriate anti-freeze mixture should be used in
colder climates as necessary.

Corrosion inhibitors reduce the formation of rust in a
cooling system. Corrosion protection can best be
provided in winter by using anti-freeze containing the
inhibitor.

Water filters should be used in areas where the water

is extremely hard and rust inhibitors cannot protect
the cooling system from the formation of rust and
scale.

Keep the radiator clean to provide maximum cooling.

Remove all dirt, lint, etc. Keep the radiator cap closed
during operation.

Check the fan belt tension periodically. For proper
operation of the water pump, the fan belt should be
tight enough to prevent slipping.

Check the water pump for wear periodically. Loosen
the fan belt and move the fan and water pump pulley
back and forth.

If

wear is excessive, replace the

bearing.

DRAINING COOLING SYSTEM

Whenever draining the cooling system for changing
anti-freeze solution or for out-of-service protection
when only water is used, be sure to open all drains
and hose connections where water could be trapped.

The following drain plugs must be removed to allow
complete flushing of the cooling system.

Radiator:

One petcock lower right front corner.

Engine Block:

One drain plug left front near water

pump.

Water Pumps:

One drain plug under cover or by

loosening cover.

If

an optional water jacket tank heater is used it should be drained
and flushed also. The lower hose must be disconnected at the tank
heater. There is no drain plug.

‘

Further information concerning the location and part
numbers for the various drain plugs throughout the
unit is shown in the

Parts

Catalog.

Onan recommends the use of clean ethylene glycol
anti-freeze solutions in closed cooling systems dur­ing normal operation and storage periods. Be sure

anti-freeze solution will protect the cooling system

during the coldest winter weather.

FLUSHING SYSTEM

Flush the system at least once a year and more often

if

operation indicates clogged passages or overheating.

To flush the system:

1.

Drain the radiator, cylinder block and exhaust
manifold.

2. Remove the inlet and outlet hoses between the
engine and radiator.

3.

Close all drain plugs and attach the flushing gun
nozzle to the water outlet, as near the exhaust
manifold as practical. Restrict the normal inlet line
opening until the system fills with water, then

apply air pressure gradually. Repeat the process

until the water from the cylinder block flows clean.

4.

Remove flushing gun.

5.

Reinstall thermostats, hoses and drain plugs and

refill the system with the proper coolant.

6.

When flushing is completed, check the system
thoroughly for any leaks uncovered by the clean-

ing operations.

BLEEDING AIR FROM COOLING SYSTEM

Air must be bled from the cooling system for proper
operation.

If

your engine is not equipped with a vent

plug in the water pump housing, install a

3/8”

pipe

plug in the top of the housing. Allow engine to cool

and bleed as follows:

1.

Fill radiator with

50-50

mix of ethyleneglycol anti-

freeze and water.

2.

Remove plug or sender from water manifold on

top of engine to vent trapped air (Figure 7b).

Replace plug or sender when water emerges from

hole.

14

3.

Remove plug on top of water pump housing

to

4-

After thermostat has opened completely, remove

vent trapped air (Figure

7b).

Replace plug when

water emerges from hole.

it

from hot water and allow

it

to cool in surrounding

air. The thermostat should close within

a

short

time.

4.

Fill radiator to proper level.

TEST1

NG

THERMOSTAT

If

a sticking or faulty thermostat is suspected, test

as

follows:

1.

Remove thermostat from cylinder head.

2.

Heat a pan of water to approximately 150°F.
Check temperature using a thermometer immersed
in water.

3.

With thermostat suspended

in

water at temper-

ature of

1

5OoF, thermostat should start to open.

5.

If the thermostat sticks or does not operate

6.

Always install a new gasket when replacing the

properly, replace it with a new one.

thermostat.

REPAIR

After making repairs on the cooling system, tighten all
connections thoroughly. Use Permatex or thread
sealing compound on all threaded connections to
prevent leaks or the entry of air into the system.

Read instructions on Permatex Sealer can before applying sealer

to

engine

parts.

WATER

MANIFOLD

PLUG

OR

SENDER

\

WATER

PUMP

W

cs-1361

FIGURE

7b.

BLEEDING COOLING SYSTEM

15

FUEL

SYSTEM

KEEP

FUEL

CLEAN!

0

DIRTY

FUEL

IS

ONE

OF

THE

MAJOR

CAUSES

OF

ENGINE

FAILURI

0

REMEMBER- EVEN A TINY PARTICAL

OF

DIRT

IN

THE INJECTION SYSTEM

MAY

STOP

YOUR

ENGINE!

0

FUEL MANAGEMENT FUEL SYSTEM

1.

2.

3.

4.

5.

Zinc or galvanized tanks should not be used as

harmful compounds may form due to reactions

with fuel oil impurities.

Pitch fuel tanks down away from fuel outlet.

The fuel system (Figure 10) consists of a glass
sediment bowl, fuel transfer pump, primary filter,
secondary filter, injection pump, injectors, and the
connecting fuel lk~es.

Use a drain cock with provisions for draining off

water and sediment.
A

fuel filterand watertrap located on tankoutlet is

good practice.

Fill

tanks on mobile equipment at end of each day

to keep condensation at a minimum.

In low temperatures,

it

is

quite common for diesel fuels

to

become

jelly-like. The point at which they cease being a liquid

is

known

as

the pour point. This quality should be watched carefully in
temperatures of

20°F

(-7°C) or lower.

Pour

Point'

Pour point indicates the suitability of fuel

to cold weather operation. Fuel should pour at 10°F

(-6°C)

below the lowest expected ambient

temperature, Figure

8.

.

INJECTION

GLOW NOZZLE

PLUG

.

CONNECTION

POINT FOR
FUEL RETURN

SECONDARY

FUEL FILTER

FUEL FILTER

FIGURE

10.

FUEL

SYSTEM

FIGURE

8.

POUR

POINT

16

Do

not use galvanized lines, fittings, or fuel

tanks in underground portions of the fuel
system. Hazardous fuel leaks may be caused by electrolytic
corrosion from moisture and chemicals in the

soil

(galvanism).
Some safety ordinances prohibit the use of galvanized materials in
fuel systems and the use of threaded cast iron fittings as well.

The fuel system, located on the service side of the
engine, uses a transfer pump to deliver fuel from the

tank to a high pressure injection pump at about

12

to

14

psi (83-97 kPa). The injection lines deliver fuel to

the injectors at high pressure and act as fuel dis-

tributors to the injectors. The time interval between
individual injectors is varied in the pump by engine
speed. From the injection pump, metered fuel is
forced through a delivery valve to the injector lines at
about 1900 psi (13,110 kPa). When the cylinder air
reaches about 1000°F (538°C) on the compression
stroke, the injector sprays fuel into the hot com­pressed air where

it

ignites. The delivery valve in the
injection pump and a pintle valve in the injector
assists the precision timed injection of fuel into the

cylinder.

.

Excess fuel is returned to the tank after each injection

cycle by a fuel return line from the nozzle. An adapter
combines the leak-off fuel with the flow-through fuel
from the injection pump. A return line connected at
this point returns the combined fuel back to the fuel
supply tank.

A diesel engine cannot tolerate dirt in the fuel
svstem. It is one of the maior causes of diesel

engine failure. A tiny piece

of

dirt in the Injection system may stop

your unit. When opening any part

of

the fuel system beyond the

secondary fuel filter, place all parts in

a

pan of clean diesel fuel as
they are removed. Before installing new or used parts, flush them
thoroughly, and install while still wet.

FILTER SYSTEM

The sediment bowl has a fine mesh screen which

blocks dirt and water entry into the transfer pump,
Figure 10. The dirt and water remain in the sediment
bowl which should be removed for cleaning as
required. The primary and secondary fuel filters are
replaceable spin-on units that clean the fuel of
extremely fine particles before it goes to the injection

pump.
These filters are mounted

on

a common casting
which bolts to the oil fill tube. Positive filtration is
assured because the engine won’t run when either
filter is loose

or

missing.

Average pore size of the second filter is

.0005

(0.0127 mm) smaller than the first filter. This means
most particles escaping the first filter are trapped in

the second filter.

Water

in

Fuel

Filters: Drain water periodically as

required from both filters. Replace primary filter every

600

hours and secondary filter every

3000

hours.
When replacing filter, tighten screw until gaskets
touch base, then tighten screw

1

to 1-1/2 turns.

FUEL TANK AND

LINES

Where a separate fuel tank

is

used, install

so

the

vertical distance from bottom of the tank to the fuel

pump does not exceed six feet. Auxiliary fuel pumps

are available to provide an additional eight-foot lift.
Avoid gravity feed of fuel to the engine. Provide a

siphon break if tank is above pump. When sharing a
fuel tank, do not connect to an existing line at a point
above the fuel supply level.

These diesel engines require a fuel supply line and a
separate return line. Install the fuel supply line from
tank to the 1/8-inch pipe inlet in the fuel pump.

Connect fuel return line to fitting at injection pump.

See Figure

10.

Use approved flexible fuel lines at the

engine to absorb vibration. Be sure there are no air

leaks in the suction line.
Install a shut-off valve in the tank for service con-

venience.

FUEL TRANSFER PUMP

The fuel transfer pump (Figure ll),

is

a diaphragm

and check valve type pump operated

by

a cam lobe on
the engine camshaft. The pump cam follower has a
wide surface to prevent wear as it rides on the

camshaft lobe. The priming lever is manually
operated to prime and bleed the system.

The diaphrgam spring maintains required fuel

pressure to the injection pump. Fuel pressure should
be 12-14 psi (83-97 kPa) when operating at 1800 rpm.

ROCKER

ARM

SPRING

...

COVER

DIAPHRAGM

ASSEMBLY

DIAPHRAGM

SPRING

ROCKER ARM

LINK

FIGURE

11.

FUEL TRANSFER

PUMP

17

Fuel pump pressure may be checked by connecting a
pressure gauge and tee at the fuel outlet. A vacuum

the pump has enough capacity to lift fuel about

6

feet

(1.83 m). The fuel pump should produce 15

to

18

inches (381 to

457

mm) of vacuum at sea level.

7. Tighten cover screws alternately and securely,
then release rocker arm.

test.

gauge

connected

at

the

fuel inlet

will

show

whether

8.

Install

pump

on

the

engine

and repeat pressure

INJECTION NOZZLES

.1.

2.

3.

4.

5.

6.

7.

Onan diesel engines use hyd raul icall y-operated,

pintle-type injection nozzles, Figure

12.

They are

factory adjusted to open at 1900 to 1950

psi

(13,110 to

13.455 kPal. However. after several hundred hours

of

Fuel Pump

Removal

Disassembly

Remove Pump inlet and outlet lines. Remove two
cap screws holding pump to engine and

lift

it off.

Notch the pump cover and body with afileso they
can be reassembled in same relative positions
and remove six screws holding them together.

operation (he nozzle pressure will decrease to about

1750

psi (12,075 kPa).

Tao bodv with a screwdriver to seDarate two

COVER

paits. Ddnot pry them apart; this would damage
d ia p h rag m.

Remove screws holding valve plate to cover and
lift out valve and cage assemblies.

Drive out rocker arm hinge pin.
Remove rocker arm, spring and link.
Lift out diaphragm assembly and diaphragm

spring.

Repair:

Transfer pump failure is usually due to a
leaking diaphragm, valve or valve gasket, Figure 11. A
kit is available for replacement of these parts.
Because the extent of wear cannot be detected by the
eye, replace all parts in the kit. If the diaphragm is
broken, or leaks, check for diluted crankcase oil and
replace.

Occasionally, failure isdue to a broken orweak spring
or wear in the linkage. In this case, replace the worn
parts or install a new pump. Obtain replacement parts
other than the repair kit from an original equipment
parts distributor.

Assembly:

1.

When installing a new diaphragm, soak it in fuel
before assembling. Insert diaphragm spring and
soaked diaphragm into pump body.

2. Insert link and rocker arm into body and hook it
over diaphragm pull rod. Align rocker arm with

-rocker arm pin hole and drive in pin. The priming
lever must be

in

position shown

in

Figure

11

when

installing rocker arm.

3.

Compress rocker spring and install between the
body and rocker arm.

4.

Insert valve cages, gaskets and valve cover plate.
Position inlet valve with spring showing and

outlet valve with spring in cover recess.

5.

Assemble cover to body with notch marks lined
up. Install screws, but do not tighten.

6.

Push rocker arm in full stroke and hold

in

this

position to flex diaphragm.

PRESSURE

A

GASKET^

SPINDLE ASSEMBLY:

ADAPTER

-

NOZZLE GASKET

NOZZLE SHIELD

SHIELD CASK NOZZLE ASSEMBLY

FUEL CUP GASKE

CYLINDER HEAD

-

A00

FIGURE

12.

NOZZLE ASSEMBLY

COVER

4

SCREW

-+

FUEL INLET

A

NOZZ LE

PRESSURE

ADJUSTING

;ING

JDLE

rDAP'

ASS

TER

4BLY

The diaphragm must be flexed, or it

will

delivertoo much fuel

pressure.

FIGURE

13.

INJECTOR

NOZZLE

HOLDER

18

Operating Principle

Nozzle operation is as follows:

1. High pressure fuel from theinjection pump enters
the fuel inlet stud and flows down drilled

passages in the body of nozzle holder, Figure

13.

2. Fuel enters fuel duct and pressure chamber of

nozzle assembly. When fuel pressure overcomes
preset pressure of the adjusting spring, the pintle
is forced upward off its seat and a fine mist of fuel
is injected into the pre-combustion chamber
where

it

atomizes and mixes with the hot com-

pressed air.

3.

If compression temperatures are high enough,

the fuel-air mixture ignites. Injection continues

until the spill port clears the top of the metering

sleeve in the injection pump and dumps the high

pressure fuel into the sump allowing the pressure

spring to close the injector and cut off fuel

injection to the cylinder.

Do

not disturb the injector pressureadjusting
screw; it cannot be reset without proper
equipment.

Excess fuel is returned to the tankafter each injection

cycle by a return line from the nozzle.

A

fuel return
fitting combines the return fuel from the injectors with
the flow-through fuel from the injection pump bleed
valve.

A

return line connected at this point returns the

combined fuel back to the fuel supply tank.

Nozzle Spray Pattern

If one cylinder

is

misfiring, its nozzle may be
operating improperly. Faulty nozzles can be checked
by loosening the high pressure line from theinjection
pump to each nozzle (one at a time).

If streamers are visible, the pattern

is

badly distorted

or

the

nozzle drips before

it

reaches opening

pressure,

it

is defective and must be cleaned or

replaced.

Cleaning is the most important part

of

nozzle maintenance. Make

sure the work area and equipment are exceptionally clean.

A

second method for determining a misfiring nozzle is

to remove the exhaust manifold and run the engine

under load. One can readily see by theexhaust which
cylinder is not operating properly.

Adjustment:

To

adjust the opening pressure, remove

each nozzle from the engine and remove the cap nut

over the adjusting screw of each. Install the nozzle to
be tested on astaticfuel nozzletesting fixture (may be
purchased from Onan). Following the instructions on

the tester, adjust the opening pressure to 1750 psi

(12.075 kPa) by turning the adjusting screw.
Clockwise increases the pressure and
counterclockwise decreases

it.

Do

not try to adjust

the pressure without a testing fixture.

Disassembly:

When removing and disassembling
nozzles, separate and label all components of each
nozzle. Never interchange components between
nozzles.

1. Remove each nozzle assembly from engine and
remove fuel inlet and return lines.

2. Clamp nozzle holder body in a vise and remove
nozzle cap nut and nozzle.

3.

Install nozzle cap nut loosely to protect lapped
surface for the holder body.

4.

If

necessary to further disassemble nozzle,
reverse pressure adjusting screw and lift out
spring and spindle assembly.

Do

not attempt to disassemble the nozzles or

adjust nozzle pressure without the propertest
equipment. A nozzle pressure tester is essential to do a satisfactory
job.

A

suspected nozzle can be checked in the field by
removing it from theengineand reconnecting itto the
high pressure line. The spray pattern (Figure 14) can
be observed as the engine is cranked.

71

Keep hands away fromaspraying nozzle! The

nozzle

discharge

pressure

can

penetrate the

skin and may cause blood poisoning or a serious skin infection.

The Cleaning procedure (Figure

15)

is extremely important when
disassembling injection equipment. Always rinse in clean fuel
before reassembling.

Injection Nozzle Tester

Testing and adjustment can be performed only with a

nozzle tester, Figure

16.

Do

not attempt to disassem-

ble the nozzles or adjust nozzle pressure without the

POOR

proper test equipment.

-

SPRAY PATTERN

:

..I

?!

.

,

Opening pressure, leakage and spray pattern can be
checked using the tester. If any of the above malfunc-

tions appear (except opening pressure), the nozzle

valve and seat can be inspected with a magnifying
glass for erosion, scoring, etc. If cleaning with solvent
does not correct the malfunctions, a new nozzle tip
will be required. Theopening pressure can then beset
and spray pattern checked.

-*.."

,:;.

.@''C

.697

h.

FIGURE

14.

NOZZLE SPRAY PATTERN

1

Use a brass type scrapertool to remove hard carbon
deposits from nozzle body valve seat.

5.

Clean nozzle valve and polish with tallow and a
wooden polishing fixture. Take care to remove all
traces

of

tallow when finished.

2.

After scraping the carbon, polish the valve seat by
using a round pointed stick dipped in tallow.
Polishing should restore seat to its original finish
unless it’s scored.

3.

Use a special hooked type scraper to clean the
nozzle pressure chamber gallery. The hooked end
of scraper is inserted into the gallery and then
carefully rotated.

6.

Examine nozzle valve and body with a magnifying
glass. If erosion and scoring conditions are found,

renew the valve and body.

7.

Use a lapping plate and compound for flat lapping
of nozzle parts which depend on a lapped surface
for sealing.

A

figure

“8’

motion is used.

CENTERING

4.

Small holes in tip

of

nozzle body can be cleaned

with a fine wire slightly smaller than the size

of

the

hole.

8.

It is essential that the nozzle body

is

perfectly

centered

in

the cap nut when reassembling nozzle.

A

centering sleeve, as shown, is used for this

purpose.

FIGURE

15.

NOZZLE CLEANING

20

FIGURE

16.

INJECTION NOZZLE TESTER

Never use hard or sharp

tools,

emery paper,

grinding powder or abrasives

of

any kind or

the nozzles may be damaged beyond use.

Soak each nozzle

in

fuel to loosen dirt. Then clean the
inside with a small strip of wood soaked in oil and the
spray hole with a wood splinter.

If

necessary, clean
the outer surfaces of the nozzle body with a brass
brush but do not attempt to scrape carbon from the
nozzle surfaces. This can severely damage the spray
hole. Use a soft oil-soaked rag or mutton tallow and
felt to clean the nozzle valve.

NOZZLE REPAIR

If cleaning will not eliminate a nozzle defect, replace
the nozzle or take it to an authorized American Bosch
service station.

Do

not attempt to replace parts of the

nozzle except for nozzle and pintle assembly.

Assembly

Rinse both valve and nozzle thoroughly before
assembly and coat with diesel fuel. The valve must be
free in the nozzle. Lift

it

about 1/3 out of the body.

It

should slide back to its seat without aid when the
assembly is held at a 45-degree angle.

If

necessary,

work the valve into its body with clean mutton tallow.

1.

Clamp nozzle holder body in a vise.

2. Set valve in body and set nozzle over it.

3. Install nozzle cap nut loosely.

4. Place centering sleeve over nozzle for initial
tightening. Then remove centering sleeve to
prevent

it

from binding between nozzle and cap

nut.

5.

Adjust to specified torque.

NOZZLE 1 NSTALLATI

0

N

Before installing the injection nozzles in the engine,
thoroughly clean each mounting recess.

A dirty mounting surface could permit blow-by,
causing nozzle failure and

a

resulting power

loss.

1. Install a new heat shield

to

head gasket

in

cylinder

head recess.

2. Install heat shield, a new nozzlegasket and nozzle
adapter.

3.

Insert nozzle assembly into recess.

Do

not strike

tip against any hard surface.

4. Install nozzle flange and two cap screws. Tighten
cap screws alternately to avoid cocking nozzle
assembly. Tighten each to 20-21 foot-pounds (27­28 Nom).

FUEL SOLENOID

The fuel shutoff solenoid (Figure 17) is also referred
to as a governorsolenoid as

it over-rides

thegovernor
during shutdown. The solenoid is mounted on the
cylinder air housing bottom pan and controls the
injection pump operating lever. When energized, the
plunger pulls into the solenoid body. When

de-energized, the solenoid spring forces the plunger
out against the operating lever to hold it in the fuel
shutoff position.

The solenoid has two coils. Both are energized for

pulling the plunger up. When the plunger reaches the

top, it opens a set of contacts, de-energizing the pull-

in coil. The other coil holds the plunger up while the

engine is running and de-energizes when the engine
shuts down.

SOLENOID

~

WIRE

TO

CONTROL

FUEL

D

TO GROUND

RETURN
FITTING

NGER AND SPRING

GOVERNOR LINKAGE

ADJUSTMENT SCREW

AND JAM NUT

JECTION PUMP

(RDJE)

IN J ECTl ON PUMP

DELIVERY VALVE CAPSCREW

FIGURE

17.

FUEL

SOLENOID

21

To

test the solenoid, check plunger operation and
current draw with 12-volt input. Current draw with the
plunger up should be about

1

amp. If

it

is much

greater, the contacts did not open.
The solenoid plunger should be adjusted

so

it

fully
stops injection when in the de-energized position. To
adjust the plunger length, screw the hex head cap
screw and jam nut on the plunger bottom

in

or out. If

the plunger sticks, remove the solenoid from its

mounting plate and clean the plunger and recess in

the solenoid.

PREHEATING CIRCUIT

This 12 volt battery circuit consists partly of manifold
heaters that heat the combustion air at the intake
manifold and a glow plug in each cylinder that heats

.

the precombustion chamber for engine starting,
Figure

18).

The manifold heater and glow plugs are

wired

in

parallel and are controlled by a preheat

switch on the control box.

GLOW

PLUG

MANIFOLD HEATER

\

FIGURE

18.

GLOW PLUG AND MANIFOLD HEATER

Check each heater by removing its lead, operating the
preheat switch, and touching the lead to its terminal.
If it sparks, there is continuity and the heater is
working. If any componentsof this circuit fail, replace
them.

Do

not attempt repairs on individual com­ponents. If there is still a question, check the compo­nent for heating.

FUEL

INJECTION PUMPS

Onan diesels are equipped with the model

PSU

fuel

injection pumps.

The fuel injection pumps are constant stroke, lapped
plunger type and operated by the engine camshaft.
They deliver an accurately measured quantity of fuel

under high pressure to the injection nozzles.

A constant bleed-check valve is furnished with all PSU pumps.The

bleed valve automatically bleedsoff a restricted amount of fuel, fuel

vapors, and small quantities of air to prevent air accumulation in the
fuel sump area of the pumps. This valve should open at pressures

between

0.9

and

3.0

psi

(6.2

and

20.7

Wa).

INJECTION PUMP REPAIR

Internal repairs on the

PSU

injection pumps require
special tools and step-by-step procedures for dis­assembly and reassembly.

Replace injection pumps that

troubleshooting procedures prove to be
malfunctioning with new pumps. Do not attempt unauthorized
repair procedures on the injection pumps.

Fuel injection pumps must pass stringent quality
inspections and tests with precise settings and ad­justments in order to meet Onan’s performance and
reliability requirements. Therefore, it must be clearly
understood by the owners and by Onan servicemen
that tampering or inept repair attempts can cause
irrepairable damage to the pumps that will not be
covered by the manufacturers warranties or ex­change agreements. Contact an authorized American
Bosch Service station or Distributor for expert repair
service on the injection pumps.

The repair service should include cleaning, part
replacement, static pressure tests for internal and
external leaks, internal pump timing, and calibration
and adjustment to the manufacturer’s specifications.

PSU INJECTION PUMP

The

PSU

injection pump (Figure

19)

is used on Onan

2-cylinder water-cooled diesels.

FIGURE

19.

PSU INJECTION PUMP

22

PSU

Pump

Operation

The pump face gear mates with and is rotated by a
drivegearon theengine camshaft, Figure20.Theface
gear, pilot ring, and the reciprocating plunger in the
pump are rotated continually to assure positive fuel
distribution. The plunger is reciprocated up and down
by a multi-lobed cam on the camshaft which bears
against a tappet assembly on the pump.

Pump

Cutaway

View

The cutaway view in Figure 21 shows the control unit

operating lever, metering sleeve, delivery valve,
plunger and drilled passages to the plunger and
injection lines.

A

timing button of very precise thickness transmits
motion from the tappet to the plunger and adjusts
plunger timing for the fuel pumped to each injector
during operation. Plunger reciprocation and rotation
are

so

phased that only one fuel injector is served

during the affective portion of each plunger up stroke.

CAM GEAR

The high hydraulic pressure developed is required to
open the pressure operated fuel injector nozzles
which inject the fuel in afine mist into thecombustion
chamber. Fuel delivery control, full load, and shutoff
are regulated by the up-and-down movement of the
fuel metering sleeve. The sleeve is controlled by the
operating lever on the outside of the pump. Fuel is
injected only during the high velocity portion

of

each

plunger up stroke.

MOUNTING

FLANGE

FIGURE

20.

INJECTION PUMP TO CAMSHAFT RELATIONSHIP

0

PE

L

LEEVE

\

TIMING BUTTON

FIGURE

21.

PSU PUMP (CUTAWAY VIEW)

23

When the tappet slips off each lobe of the camshaft,
the spring loaded plunger

is

forced down opening the

fuel supply

port

to the fuel sump. This allows fuel

under low pressure from the transfer pump and fuel

sump to

fill

the cavity between the top end of the
plunger and the delivery valve. The plunger is then
ready for the up stroke.

Metering Sleeve Operation

The metering sleeve is positioned by the operating
lever of the governor control unit, Figure

22.

An
eccentric pin on the end of the control shaft engages a
slot in the metering sleeve

so

that a slight rotation of
the control shaft causes the sleeve to ride up or down
on the plunger. As the camshaft and face gear rotate,
the drive key and a vertical

slot

in the face gear

transmit rotation to the plunger. Rotating the plunger

aligns the plunger outlet groove with the proper
injection line outlet for the injector to be fired on each

pump stroke.

FIGURE

23.

SHIM

THICKNESS

Removing Tappet

Be sure to hold the pump drive securely to the
pump body when removing the tappet, Figure

24.

If

not, the pump

will

come apart and be difficult to reassemble.

Also, the metering sleeve may drop

off

the plunger into the sump

when the plunger is removed.

If

the mechanic

Is

not aware

of

it, he

could put the pump back together, but it will not operate.

If

the
plunger port is not enclosed by the sleeve, there will be no fuel
delivery.

'

SLEEVE

Use a pair

of

channel

lock

pliers or a screwdriver to remove the

tappet

from

the O-ring

in

the drive gear.

MAXIMUM

THROTTLE

STOP SCREW

STAMPED CODE

LETTER

OF

BUTTON

USED

FIGURE

22.

METERING CONTROL

Pump Installation Shims

If

the pump is removed from the engine, be sure the

steel shims between the pump and the crankcase

mounting are the same on reassembly to maintain
proper gear backlash, Figure

23.

The number
stamped on the crankcase indicates the proper shim
thickness. This thickness does not change when a

new pump is installed.

It

only changes when a new

crankcase is installed, and then the thickness of the

proper shims is stamped on the new crankcase.

TTON

O-RING KEEPS TAPPET IN

DURING HANDLING

FIGURE

24.

TAPPET REMOVAL

24

TABLE

1.

TIMING

BUlTONS

16orS

15

or

R

14orP

13

or

N

12orM

GROUP

1

I

GROUP

2

I

CODE I PARTNO.

I

SI

147-0186
147-0187
147-0188
147-0189
147-0190

I

I

I

Inch

~~

-134
.131

-128
.125
.122

I

CODE I PARTNO.

I

S

mm

147-0161

Button

12

or

Y

is

the mid-range

of

the button sizes used the most.

The button dimension is determined by the number or letter

stamped on its side, Figure

25.

BUTTON WITH CODE LETTER

OR

NUMBER STAMPED ON

IT.

FIGURE

25.

TAPPET BUTTON CODE

TIMING BUTTON

CODE

The timing button has a code number or letter which
corresponds with its dimension in thousands of an

inch. See Table

1.

Figure

26

shows the timing button
and tappet relationship. Only one button is required
to provide the correct port closing.

TIMING

BUTTON

FIGURE

26.

TIMING BUTTON AND TAPPET

3.023

2.946

2.870

2.794

2.718

2.642

PORT CLOSING FORMULA

The formula for determining the proper port closing

(PC) timing button for a new or replacement pump is

as follows:

1.

Remove old pump.

2.

Determine total pump flange and button
thickness for old pump.

a. Write down dimension given on old pump

flange. See Example:

Inches (mm)

Port

closing dimension

of

old pump

1.109 (28.169)

Bu!ton thickness

of

old pump

+.lo7 (2.719)

Total

1.216 (30.887)

Port

closing dimensions

of

new pump

-1.094 (27.788)

Required button thickness

of

new pump

.122 (3.099)

b. Remove old pump timing button.

Be careful when removing tappet
assembly that the plunger doesn't

drop out of the sleeve, because reassembly is difficult.

c. Obtain dimension of old timing button from

Table

1

corresponding with number or letter

code on timing button.

d. Add dimension on old pump flange to timing

button dimension.

Service Bulletin Engine

34

Is enclosed with each new pump to

enable the installer to correctly time the pump to the engine.

PREPARATION

FOR

PUMP

INSTALLATI ON

1.

The crankshaft must be set on the compression
stroke

for

No. 1 cylinder.

2.

Look into hole in block where pump mounts to
verify that one intake valve lobe points outward
and down

45

degrees.

25

3.

See that

PC

mark on flywheel aligns with timing

pointer on gear case cover, Figure 27.

4.

Align

PC

mark on flywheel to timing pointer by

rotating crankshaft clockwise in the direction of

engine rotation to take out all gear backlash

in

that direction.

INSTALLING PUMP

Another method of aligning the drive gear slot for

pump installation uses a straight edge as shown. An
experienced person can “eye ball” the slot in the
screw hole and place the pump on the engine with
proper gear teeth meshing.

.-

The flat area just above the pump has a number markedonit which

refers to the shim thickness required between the pump and its

’

mounting pad

for

assuring proper backlash in the gearing. Don’t

forget the

shims.

With the pump drive gear locked by the 1/8-inch

(3.18 mm) brass rod, position the pump in the hole
(Figure 29) and firmly apply pressure. The arr0.w on
Figure 29 shows the position of the injection pump

cam and gear on the camshaft. A slight spring

reaction indicates the pump and camshaft gears are
meshed. Maintain this pressure, remove brass rod
and rotate the crankshaft manually to make sure the
gears mesh properly, Figure

30.

Install mounting

screws and torque to 15-16 ft. Ib. (20-22 Nom).

1111

I,,,

<.c.

9==++==

P.C. (PORT CLOSING)

GEAR COVER

p::.:::

’’

C’

.

FIGURE

27.

PORT CLOSING POSITION

POSITIONING PUMP ON ENGINE

Remove the screw shown on the side of the pump,
rotate drive gear, and insert

a

1

/8-inch (3.1 75

mm)

brass rod into the slot in the drive gear to lock the gear
for positioning the pump on the engine, Figure 28.

ROTATE FACE GEAR UNTIL

BRASS

RODS

SLlFS

INTO PLACE LOCKING

.FIGURE

29.

INSTALLING PUMP ON ENGINE

PUMP TAPP

CAM

GEAR

FIGURE

28.

LOCKING THE DRIVE GEAR FIGURE

30.

PSU PUMP INSTALLED

DELIVERY VALVE

FU

NCTl

ON

The delivery valve maintains 300 to

600

psi

(2070

to

4140 kPa) line pressure

in

the injector lines with the
engine running, Figure 31. This pressure increasesto
about 1900 psi (13110 kPa) on each stroke of the

injection pump plunger. The trapped fuel is held

in
the lines at all times, even though the pressure bleeds
off during shutdown periods. When the lines are full of
fuel, onlyacoupleturnsof thecrankshaft are required
to build up enough line pressure for firing the

injectors.

SPRING

DELIVERY VALVE

\

/

.SEAT

.IN€ PRESSURE

DELIVERY VALVE

CAP NUT GASKET

CAP

NUT

\

(Torque

to

55-60

foot-pounds)

FIGURE

32.

DELIVERY VALVE ASSEMBLY

RETURN LINES

UEL RETURN

LINE HERE

(Flexible

Line)

FIGURE

31.

DELIVERY VALVE CLOSED-PLUNGER DOWN

FLOW

TIMING

THE

PSU

PUMP

Flow timing the injection pump can bedone using fuel

to determine whether or not the proper timing button

has been installed for best operating conditions. In
case the pump is removed without recording the PC
dimension and the timing button thickness, it is
necessary to flow time the pump to establish the exact

PC position.

1.

Install

No.

12 timing button in PSU pump as

previously discussed under preparation for pump

installation.
Remove delivery valve cap and holder; take out
spring and replace holder and cap, Figure

32.

2. Remove door panel, air cleaner, and top sheet
metal cover for access to flywheel marks and fuel
system.

3.

Remove

No. 1 injector line; re-install line with top

end of line in pump outlet

so

other end will direct

fuel flow into an open container, Figure 33.

FIGURE

33.

FUEL LINES TO INJECTORS

4.

Place container under open end of

No.

1 line.

5.

Disconnect governor linkage at ball joint and
wedge control arm at maximum fuel position.

6.

Rotate flywheel counterclockwise (when facing

front of engine) to point where PC mark on

flywheel is about 15 degrees before timing pointer
(compression stroke

No.

1

cylinder).

Check that front cyllnder valve rocker arms (both valves) are

free

to move lndlcatlng the valves are closed.

7.

Manually operate fuel transfer pump until air-free
fuel flows steady from end of

No.

1 line into

container.

27

8.

9.

If fuel tank is disconnected, use a separate container

of

fuel
and connect a short hose line between the transfer pumpinlet
and the fuel container. The pump has enough suctlon

(1

5

to

18

inches

[381

to

399

mm]

of vacuum) to

pull

the fuel

out

of the

container.

Continue transfer pump operation while assistant

rotates flywheel slowly in clockwise direction.

TIMING BUTTON THICKNESS

Injection

pump

kits

a

pump

and

four

buttons

which will time 90 percent of the engines. The
standard thickness button and ring spring are no
longer assembled, but are loose

in

kit.

Stop flywheel rotation at exact point

fuel

stops

flowing from

No. 1 lineintocontainer(onedropin

2

to

5 seconds).

l-his

point

is

the

port

closing

time

of

the

injection

pump

plunger

regardless

of

flywheel position, Figure 34.

Pump timing is critical. The injection pump on each
engine must be timed

to

that particular engine by

using a timing button of specific thickness. Use the
method which applies best to determine the correct
new button thickness. Each new pump has its own

port closing dimension stamped on it.

FILL

PORT

(PC)

FIGURE

34.

PORT CLOSING

Timing is correct if port closing occurs when the PC mark on
the flywheel aligns with the timing pointer. If it doesn't match,
timing is either early

or

late and another timing button is

required, Figure

35.

FIGURE

35.

PORT CLOSING (PC) MEASUREMENT

Procedure

1.

Mark flywheel in 0.1-inch (2.54 mm) graduations
(about five marks each direction) from PC mark

for calculating required change

in

button

thickness.

2. Measure distance in tenths (or mm) from PC mark
on flywheel to point of actual port closing.

3. Multiply distance measured times .003 inch

(.076 mm) to determine the difference in

thickness required for new button.

One degree of crankshaft rotation equals the 0.1-inch gradua-

tion or .OO&inch button thickness for timing.

TIMING CALCULATION

0.3'

x

.003"

=

.009"

(7.6 x .076

=

.228

mm)

Example

A.

The port closing time

is

late

by 0.3-inch

(7.6 mm) measurement, Figure 36.

POINTER POINTER

EXAMP

LEA

'

FLYWHEEL

FIGURE 36. TIMING MARKS

Since .1 inch (2.54 mm) equals .003 inch (7.6 mm)

button thickness, the installed button is too thin by
.009 inch (0.229 mm). This means a button

.009

inch

(0.229 mm) thicker than the one installed is required

to time port closing

so

PC mark on flywheel aligns at

the timing pointer when fuel flow stops.

Example B.

If

PC

timing is

too

early by 0.4 inch

(10.2 mm), multiply 0.4

x

.003 = .012 inch (10.2 mm

x

'7.6 mm = 0.305 mm).

In

this case, a thinner button
.012 inch (0.305 mm) less than the one installed is
required.

28

BLEEDING FUEL

SYSTEM

Bleed fuel system whenever the filtersare changed or
when there is air in the lines.

Procedure:
Manually actuate fuel transfer pump until air bubbles

are all out and clear fuel flows from the bleed valve
automatically, Figure

37.

If

the transfer pump cam lobe

is

on the high side, the priming lever

will not operate the pump. Rotate the flywheel one revOh!iOn

before operating the priming lever.

BLEED VALVE

FUEL

RETURN

CONNECT

FUEL

LINE

(

RDJE)

FIGURE

37.

BLEEDING FUEL

SYSTEM

29

OIL

SYSTEM

Onan diesel engines have pressure lubrication to all
working parts of the engine. The oil system includes
an oil intake cup, a gear-type oil pump, a by-pass
valve, a full-flow oil filter and passages and drillings
through the block for oil delivery.

Figure

38

shows the pressure oil system.

A

thin film of oil from the crankcase lubricates the

cylinder walls and the rings wipe the excess oil off to

prevent passage of oil to the combustion chamber.

The upper portion of the cylinders are partially
lubricated by the fuel. The connecting rod bearings
are critically in need of lubrication because of the

high pressures and high rotating speeds. Bearing

lubrication and cooling are very important to the life
of an engine.

Normal oil pressure should be

25

psi

(172.5

kPa) or

higher when the engine is at operating temperature.

If

pressure drops below

20

psi (138 kPa) at governed

speed, inspect the oil system for faulty components.

OIL

PUMP

The oil pump is mounted on the front

of

the crankcase
behind the gear cover and is driven by the crankshaft
gear.

The pump drawsoil from thecrankcase anddeliversit
through the oil filter to the rocker housing, drillings
through the crankcase to the crankshaft bearings,
camshaft front bearing, crankshaft passages to con-

necting rod bearings and connecting rod passages to
piston pin bushings.

Removal

1.

Remove gear cover and

oil

base. (See

ENGINE

2.

Unscrew intake cup from pump.

3.

Remove crankshaft lock ring and gear-retaining

4.

Loosen two cap screws holding pump and

DISASSEMBLY.

washer.

remove pump.

FIGURE

38.

OIL

PRESSURE

SYSTEM

Repair

Except for the gaskets, component parts of the pump

are not individually available.

If

the pump is defective
or excessively worn, replace it. Disassemble the
pump by removing the two cap screws holding the

pump cover to the body. Inspect forexcessive wear in
gears and shafts. To improve pump performance,
adjust the gear end clearance by changing the gasket
thickness between the pump body and cover. Usethe
thinnest gasket that permits free movement of the

pumpshafts. Oil all parts when assembling the pump.

Installation

Before installing,

fill

the pump intake and outlet with

oil to be sure

it

is primed. Mount the pump on the

engine and adjust the 0.005-inch

(0.127

mm) lash

between the pump gear and crankshaft gear. Mount
the intake cup on the pump

so

it is parallel to the

bottom of the crankcase.

30

BYPASS

VALVE

REAR BEARING

B>

PLATE

--L

OIL

BYPASS

I

OIL

BYPASS

FIGURE

39.

BYPASS

VALVE

NOTE

I

-USE

A

ff70

DRILL

(.OB)

(.71

d

FOR CLEANING AREA

1.

NOTE

2

-

USE A

#56

DRILL

(-046)

(1

-

17

ttd

FOR CLEANING AREA

2.

W

FLUSH

ROCKER

BOX OIL

LINE

WITH

FUEL AND CLEAN HOLES

WITH

FINE

WIRE.

Located on the outside of the rear bearing plate, the
bypass valve (Figure

39)

controls oil pressure by
allowing excess oil to flow directly back to the
crankcase. Normally thevalve begins to open at about

25

psi

(172.5

kPa).

It

is non-adjustable, and normally

needs no maintenance.

To

determine

if

high

oil

pressure

is

caused by the
plunger sticking closed, or low oil pressure by the
plunger sticking open, clean and inspect the valve.

To

remove the valve, unscrew the recessed plug

in

the

rear bearing plate and lift out the spring and plunger

assembly. Determine proper valve operation by

checking the spring and plunger against the given
values:

Plunger Diameter..

. .

. . 0.3365

inch to

0.3380

inch

Spring

(8.5471

to

8.5852

mm)

Free Length..

..

. .

..

.

2-5/16

inches,

+ 1/16

inch

(74.613, + 1.588

mrn)

2.225

Ib.

at

1-3/16

inches (compressed)

at

(30.163

mm)

(compressed)

(1.01

kg)

ALL Z-CYLINDER

DIESEL MODELS

FIGURE

40.

CLEANING ROCKER

BOX

OIL LINE AND RESTRICTION ORIFICES

31

‘CRANKCASE

BREATHERS

OIL LINES

At overhaul time the rocker box oil line should be
flushed with fuel, and a fine wire used to clean the
small holes, Figure 40. Clean standpipe breather on
four cylinder engines.

Clean out all other oil lines and drillings with com-

pressed air whenever the engine is disassembled or

overhauled. Reach the

oil

gauge passage by remov-

ing the oil filter mounting plate.
External oil lines, the rocker box oil line, and the

internal oil line to the rear bearing are replaceable, if

damaged.
Restriction orifices are placed in the external oil lines

to regulate thequantity of oil delivered to theinjection

pump gearing and tappet and to the rocker arm and
valve train areas. Two orifices are located in the Tee
fitting at the injection pump and one orifice is located

in the inlet fitting to each cylinder head.

To

prevent injection pump or valve train

Ex3

damage from lack

of

lubrication, ensure that
ail restriction orifices are kept open. Cleaning can be done using a
fine wire or drill bit and compressed air.

CAUT,ON

.028

inch size at heads (0.71 mm)

.046 inch size at Tee (1.17 mm)

..

OIL FILTER (Full Flow)

..

.

The oil filter is mounted on the filter plate at the left

side of crankcase, Figure 41.

It

requires replacement

every

500

hours of normal operation. Removefilter by

turning counterclockwise using afilter wrench. Install’

new filter finger-tight plus 1/4 to 1/2 turn.

FIGURE

41.

FULL FLOW

OIL

FILTER

The

RDJE

crankcase breather has a valve assembly

that compensates

for

the pulses created by both
pistons moving up and down at the same time. The
ball check valves close as the pistons move up and are

forced open as the pistons move down, thus, venting
crankcase pulse pressure and fumes

to

thecarburetor

intake hose. The only maintenance required is to

clean the check valve assembly and replace the baffle

material periodically. Remove the hose clamp,
breather hose, and cap clamp to release the breather

cap and valve assembly, Figure

42.

Wash the cap,

valve assembly, and baffle material

in

a suitable

solvent and reinstall.

The

RDJEA

crankcase is vented by a breather pipe
installed in the intake manifold, under the valve cover.
A

breather hose between the crankcase and the valve

cover vents the crankcase pressure and fumes to the

intake manifold.

Since one piston moves up while the other moves
down, pulse pressure is minimal;

it

is equalized by the

pistons moving

in

opposite directions.

-

-

BREATHER

HOSE

HOSE

CLAMP

\

VALVE

7

“0”

RING

’

SCREEN

/

CAP AND

/

A

-

CLAMP

BAFFLE

FIGURE 42. CRANKCASE BREATHER

OIL DRAIN EXTENSION

For service convenience, install a short (less than

10

inches

[254

mm]) oil drain extension made from

standard pipe and fittings

in

the l/Pinch (12.70 mm)

pipe-tapped oil drain hole in the base.

32

The purpose of the engine governor is to maintain a
constant engine speed during changes in power
demands. A governor responds to changes in power
demands by varying the throttle position.

A

constant-

speed governor is standard on industrial engines.

GOVERNORS

The constant-speed governor (Figure

43)

maintains

engine speed up to 2400-rpm. The speed-sensing

device is a ball and cup mechanism on the camshaft

gear.

A

yoke, resting on the cup, is connected to the
governor arm which, in turn, is connected to the
throttle lever. Any change in engine speed is
transmitted from the cup to the yoke, and on to the
throttle.

Maintenance:

The linkage must

be

ableto move freely

through its entiretravel. Periodically lubricate

the

ball

joints with graphite or light non-gumming

oil.

Also
inspect the linkage for binding, excessive slack, and
wear.

Testing and Repaie

Removing the gear cover for

access to the governor cup and other internal gover-

nor parts is covered in the

ENGINE DISASSEMBLY

section. External service and repair is limited to
testing spring tension and checking ball joints.

To

test spring rates, use aspring-type scale. Compare

the measured rates with those

in

Table 2.

TABLE 2. GOVERNOR SPRING DATA

Tension on the governor spring determines the speed
at which the engine is governed. A stud screwed into
the spring is used to vary the number of effective coils
for getting the desired sensitivity-the speed drop
from

no

load to full load.

Engine Governor Spring No

Load

Active

Constant

150-0846

1-3f8

13-m

1

;:

1

Type

1

Number

I

Length

I

Coils

I

(34.925

mm)

8435

DECREASE

SENSITIVITY

FIGURE

43.

GOVERNOR ASSEMBLY AND ADJUSTMENTS

33

ADJUSTMENTS

Speed Adjustment:

To change the governor speed,

change the spring tension by turning the governor
spring tension) to increase

RPM

and

COUNTERCLOCKWISE

tachometer against flywheel cap screw.

spring nut (Figure 44). Turn the nut clockwise (more
counterclockwise to reduce governed speed. Hold a

TURN NUT

TO DECREASE SPEED

Sensitivity Adjustment:

To adjust governor sensitivity

(no load to full load speed droop) turn the sensitivity

GOVERNOR SPRING

NUT

Sdjusting ratchet accessible through a covered
access hole on the side of the blower housing.

sensitivity (more speed drop).

If

the governor is too

Counterclockwise gives more sensitivity (less speed

drop when full load is applied), clockwise gives less
sensitive, a rapid hunting condition occurs (alternate

increasing and decreasing speed). Adjust for max-

imum sensitivity without hunting. After sensitivity

8419

SENS ITlVlTY

GOVE

SHA

TURN

RATCHET

CLoCKWISE

TO DECREASE SENslTIv1.V

TURN RATCHET COUNTER-

CLOCKWISE

TO

INCREASE

adjustment, the speed will require readjustment. After
adjusting the governor, replace the knockout plug in
the blower housing and secure speed stud lock nut.

Excessive droop may be caused by engine mlsflrlng. Correct this

condition before adjustlng governor.

FIGURE

44.

GOVERNOR ADJUSTMENTS

34

STARTING

SYSTEM

These models use a separate

12

volt starting motor

mounted on the right hand side of the engine to drive

the flywheel.

It

is a standard automotive starting
motor with a solenoid for engaging the pinion and an
over-running clutch. When the solenoid is energized,
its core pulls in, shifting the pinion into engagement
with the flywheel

ring gear. At

the

same time,

contacts in the solenoid close to provide a circuit for

the starter motor. The starting motor remains engaged

until the starting switch is released.

If

engine

is

equipped with a start-disconnect switch, the starter
motor will automatically disengage flywheel gear when engine
speed reaches about

900

rpm.

The starter is protected from over-speed

by

an over-

running clutch which permits the engine to run faster

then the starter before the pinion is disengaged.

Figure

45

shows the starting circuit.

MAINTENANCE

Periodically check the starting circuit wiring for loose
or dirty connections. Inspect the starter commutator
and if

it

is dirty, clean with number

00

sandpaper (do
not use emery cloth or emery paper). Check the
brushes for poor seating on the commutator and for

excessive wear.

TESTING

Poor cranking performance can be caused bya faulty

starting motor, defective battery, or high resistance in
the starting circuit.

Check the charge condition of the battery with a

hydrometer.

Specific gravity should be between 1.290 and 1.225
when

75

percent charged. If not, recharge the battery.

Check electrolyte level.

If

battery will not recharge,

replace it. Keep battery connections tight and clean.

With

the starting motor operating, check the voltage

drops

(1)

from the battery ground terminal post (not
the cable clamp) to the cylinder block, (2) from the
cylinder block to the starting motor frame and

(3)

from the battery positive post to the battery terminal

stud on the solenoid. Normally, each of these should
be less than two volts.

If

extra long battery cables are

used, slightly higher voltage drops may result.

Thoroughly clean all connections in any part of the

circuit showing excessively high voltage drops.

If

starting motor tests are required, remove the motor
from the engine and test it on a bench. Test the free­running voltage and current.

TO

START SOLENOID

GROUND CONNECTION

TO

ENGINE

nnnnn

FIGURE

45.

STARTING SYSTEM

Using a spring scale and torque arm, test the stall

torque, Figure

46.

Multiply the spring scale reading by

the arm length for the torque value.

If

free running speed is low, and starter has a high
current draw with low stall torque, check for tight,
dirty or worn bushings, bent armature shaft, or loose
field pole screws, allowing armature

to

drag. Check

also for shorted or grounded armature and field.

A

lowfreespeed with lowtorqueand low currentdraw

indicates an open field winding, high internal
resistance due to poor connections, defective leads,
broken or worn brushes, or scored, worn, or dirty
commutator.

35

VARIABLE RESISTANCE

STALL

POS-

BRAKE

ARM

I----

12"-4

FIGURE

46.

TESTING

STALL

TORQUE

High free speed with low developed torque and high
current draw indicates shorted fields. Since there is
no easy way to detect shorted field coils, replace and
check for improved performance.

The voltage drop across the solenoid on the starting

motor should be less than

1.5

volts, if not, remove it

for repair.

REPAIR

Armature:

Inspect the armature for mechanical

defects before checking for grounds or shorted coils.
To

test for grounds, use a l2volt test lamp and check
between each segment of the commutator and the
shaft.

Do

not touch probes to the commutator brush

surfaces, as this will burn the smooth surfaces.

A

growler is necessary to test for shorted coils. With
the armature in the growler, run a steel strip over the
armature surfaces.

If

a coil is shorted, the steel strip
will become magnetized and vibrate. Rotate the
armature slightly and repeat the test.

Do

this for one
complete revolution of the armature. If the armature
has a short or ground, replace it.

If the commutator is only dirty or discolored, clean

it

with

00

or

000

sandpaper. Blow the sand out of the

motor after cleaning.

If,

however,

it

is scored, rough

or worn, turn it down in a lathe.

Field Coils:

Using a test lamp and probes, check the
field coils for grounding to the motor frame or open
circuit. Inspect all connections to be sure they are
properly clinched and soldered. Inspect the insulation

for evidences of damage. The only way to check for
field coil shorts is to use the starting motor test.

Brushes:

Check the brushes for wear or improper
seating. They should slide freely in their holders.
Check the brush spring tension with a spring scale.
To change spring tension, twist the spring at the
holder with long nosed pliers.

Replace Prestolite brushes when excessively worn,
orwhen worn to 5/8inch in length. Replace Mitsubishi,
brushes when excessively worn or when worn to 3/8
inch in length. Some brushes aresoldered to the field
coil. To remove these brushes, unsolder the lead and
open the loop in the field coil lead. Insert the new
brush pigtail completely into the loop and clinch
before resoldering.

A

good soldering job is necessary
to ensure good contact and low voltage drop across
the connection.

Over-running Clutch:

Clean the clutch thoroughly

but do not dip in solvent.

It

cannot be repacked with

grease.

It should slide easily on the armature shaft with no

binding. Turn the pinion,

it

should rotate smoothly,
but not necessarily freely. Reverse the direction a few
times and

it

should instantly lock and unlock. Replace

the clutch if operation is defective or pinion is worn

or

damaged.

Shifting Solenoid:

See that the plunger moves freely

in the coil. Check pull-in coil continuity between the
solenoid control terminal and the solenoid connection
to the motor. Check the hold-in coil continuity
between thesolenoid control terminal and ground on
the motor.

Bearings:

If either the front or rear bearings show

excessive wear, replace them. Drive the

old

bearings
out, and using an arbor press and the proper arbor,
press new bearings into place.

36

SHIFTING

1

SOLENOID

SOLENOID

PLUNGER

FIGURE

47.

STARTING

MOTOR

PRESTOLITE STARTER REMOVAL

AND DISASEMBLY

1.

2.

3.

4.

5.

6.

7.

8.

9.

IO.

11.

Remove connections to controls and battery at

shifting solenoid. Figure

47.

Remove

nut

holding rear mounting bracket to the

engine.

Remove three cap screws holding starting motor

flange to engine and pull out motor.

Remove link pin holding theshift lever tosolenoid

plunger and remove shift lever center pin.
Remove through bolts from commutator end of

motor. Pull off end cover and lift brushes off their
seats.

Pull pinion housing from front end of motor and
lift armature and clutch out of motor frame.

To

remove over-running clutch from armature,
drive retainer away from lock ring near front end
of shaft, remove lock ring and pull assembly off.

Do

not attempt to disassemble clutch assembly.

If

necessary to service solenoid, remove four cap

screws and electrical connection holding

it

to
motor frame. Remove two screws on rear of
solenoid to reach switch contacts.

If

necessary to remove starting motor flange

(Figure 48), watch for shims between flange and

crankcase surface. Save any shims,

as

they must

be reinstalled to position the starter correctly.
Mount starter motor to engine by a direct reversal

of the removal procedure. Connect battery cable
and wires to starter.

Connect battery cables to battery. Connect

ground cable last.

37

-STARTING

MOTOR

FIGURE

48.

STARTING MOTOR SHIMS

PRESTOLITE STARTER ASSEMBLY

Before assembling, soak the bronze bearings in oil.
They are absorbent bearings, designed to hold up to
25 percent of their own weight in oil. Be sure the felt
oil pad is in the outer end

of

the commutator end

bearing.
When the motor

is

assembled, check the armature
end play. ltshould be between 0.005-inch (0.127 mm)
and 0.030-inch (0.762 mm). Adjust end play by
adding or removing washers on the commutator end
of the armature.

Before installing, check the pinion clearance. Proper
clearance is important to ensure starter engagement.
Press on solenoid core to shift the pinion into full
mesh and measure the clearance between pinion and
pinion stop, Figure 49. This should be between 0.07­inch and 0.12-inch

(3.05

mm) (as near to 0.070-inch

[1.78 mm] as possible.) Adjust the link screw on the

end of the solenoid plunger for proper clearance.

PUSH PLUNGE

ENGINE TO MAKE THIS

MEASUREMENT

FIGURE

49.

PINION CLEARANCE

MlTSUBlSHl STARTER REMOVAL
AND INSTALLATION

1.

Remove both battery cables from battery. Dis-

2.

Disconnect battery cable and electrical lead wires

3.

Remove capscrews and flat washers that attach

4.

Remove starter.

5.

Mount starter motor to engine by a direct reversal

of

the removal procedure. Connect battery cable

and wires to starter.

6.

Connect battery cables to battery. Connect
ground cable last.

MlTSUBlSHl STARTER DISASSEMBLY

connect ground cable first.
from starter.
starter to mounting bracket.

1.

Remove

“M”

terminal nut and wire lead from

solenoid.

2.

Remove the two solenoid mounting screws and
remove solenoid.

3.

Remove the

two

through bolts and brush holder
retaining screws. Remove rear bracket (Figure
49a).

THROUGH

BOLTS

e

ES-1186

FIGURE

49a.

REMOVING REAR BRACKET

4.

Remove frame assembly, and brush holderassem­bly while pulling the brushes upward. Then re­move armature assembly.

5.

Remove cover assembly, (snap ring and washer)

from the pinion shaft (Figure 49b).

ES-1195

SNAP RING

FIGURE

49b.

REMOVING SNAP RING AND WASHER

6.

Remove capscrew that secures center bracket to
front bracket. Remove the center bracket; several
washers used to adjust pinion shaft end play can
now be removed (Figure 49c).

FRONT CENTER

BRACKET BRACKET

T

WASHERS

-

CAPSCREW

--

-

ES-1187

FIGURE

49c.

REMOVING CENTER BRACKET

38

7.

Remove gear, spring set and lever assembly from
front bracket. Note direction in which the lever
assembly is installed.

8.

Push pinion gear and stopper down and remove

retainjng ring. Remove stopper, pinion gear,
spring, and pinion shaft assembly.

9- Inspect ball bearings. If they are rough or noisy

when rotated replace them. The front bearing is

not replaceable and must be replaced with the

bracket.

SOLENOID

FIBER

I

TERMINAL

"M"

THROUGH

(RETAINING

RING)

I

BRUSH

HOLDER

/

FRAME

ASSEMBLY ASSEMBLY

MlTSUBlSHl STARTER ASSEMBLY

XES1255

FIGURE

49d.

MlTSUBlSHl

STARTER

For assembly reverse the disassembly procedure, but

note the following items. See Figure 49d.

Whenever starter motor

is

disassembled apply grease

to each

of

the following points. (Recommended

grade; Multemp PS

No.

2.)

Armature shaft gear

Reduction gear
Ball bearing (Both ends

of

armature
Stopper on pinion shaft
Sleeve bearing
Pinion gear
Sliding portion

of

lever

Pinion Shaft End Play Adjustment

Adjust end play

so

that

it

is

0.1

to

0.8

mm (.0039 to

.0315

inch) with theadjusting washers placed between

center bracket and reduction gear (Figure 49e).

PINION SHAFT

OVERRUNNING

CLUTCH

\

PINION

GEAR

I

SNAP RING

ES-1191

FIGURE

49e.

ADJUSTING PINION

SHAFT

END PLAY

With pinion gear removed, install reduction gear onto

pinion shaft. Place pinion shaft into center bracket
and secure with washer and snap ring. Measure the
end play with a feeler gauge between center bracket
and gear.

If

necessary, adjust end play by adding

or

removing adjusting washers.

If

pinion gear has not been removed, place pinion
shaft and reduction gear between front bracket and
center bracket. With lever spring removed and bolt
tightened, push pinion shaft out and measure end
play. Adjust end play if necessary by adding

or

removing shims.

Pinion Gear Installation

Place spring and pinion gear onto pinion shaft. Slide
stop ring onto pinion shaft and install retaining ring in
groove. Pull stop ring over retaining ring (Figure49f).

-2

STOP / RING

STOP RING

r

I

SNAP RING

ES-1194

FIGURE

491.

PINION GEAR INSTALLATION

Lever Assembly Installation

Figure 499 shows the correct method of installing

the

lever assembly, spring, and packing. Pay close
attention to direction of lever.

PACKING

LEVER

I

CENTER

BRACKET

LEVER

SPRING

II

ES-1185

FIGURE

49g.

LEVER INSTALLATION

Pinion Gap Adjustment

After assembling starter motor, adjust pinion gap.

1.

Remove

“M”

terminal nut and wire from solenoid.

2.

Connect positive terminal

of

battery to “S” ter­minal on solenoid and negative terminal to starter
body. With battery connected pinion gear will

shift into the cranking position.

3.

Gently push pinion shaft back towards front
bracket and measure the amount of travel (Figure

49h).

PINION

\

I

AMOUNT

OF

TRAVEL

I

r

Y

(PINION GAP)

I

ES-1192

FIGURE

49h.

PINION GAP ADJUSTMENT

4. The pinion gap should be

0.3

to

2.0

mm

(0.018

to

.0787

inch). Adjust by changing the number of fiber

washers used

on

solenoid mounting surface.

Increasing the number of fiber washers decreases

clearance. Decreasing the number

of

washers

increases clearance.

BELT DRIVEN

(35

AMP) BATTERY CHARG-

ING

ALTERNATOR

(Optional)

This information

is

presented for field use only. Major

repair should be done in the shop.

Brush Assembly Removal

Remove brushes as follows:

1. Remove three screws which fasten voltage

2. Disconnect regulator leads and remove regulator.

3.

Remove two screws on phenolic coverand lift out

4.

Pull brush assembly straight up and lift out.

5.

Reverse procedure for assembly, Figure

50.

regulator to alternator.

cover and gasket.

Brush Assembly Tests

Test brush assembly as follows:

1. Connect an ohmmeter or test lamp (12 volts) to
the field terminal and to the bracket. The test lamp
shouldn't light or resistance reading should be

high (infinite). If not, there is a short and the

assembly must be replaced.

2. Move one ohmmeter lead from the bracket to

insulated brush. Use an alligator clip directly on

the brush. Be careful not to chip

it.

Resistance

reading should be zero (continuity).

3.

Connect ohmmeter leads to the grounded brush
and the bracket. Resistance should be zero

(con

ti

nu i ty)

.

VOLTAGE REGULATOR

MOUNTS

HERE

FIGURE

50.

OPTIONAL, BATTERY CHARGING,
EXTERNAL ALTERNATOR

41

ENGINE REBUILDING

When engine disassembly

is

necessary, remove com­plete assemblies (tear down individual components
like fuel pump, breaker mechanism, etc., as bench
jobs).

Use special tools available.

Disassembly:

1. Common sense will dictate proper order of dis­assembly. As disassembly progresses, the order

may be changed, as will become self-evident.

a. Radiator, water pump.
b. Flywheel-using puller or pry-bar method.
c. Gear Cover-protect oil seal from keyway

d.

Crank Gear-use puller and gear puller ring.

e. Loosen accessories such as fuel pumps and oil
f. Starter motor.

2.

A suggested procedure would be as follows:

damage.

filter.

g. Drain oil

-

discard oil removed.

h. Cylinder head.

i.

Valves, springs, rocker arms.

j. Camshaft and gear, rear bearing plate, oil

k. Piston, connecting rod bearings.

I.

Crankshaft.

rn.

Try to analyze reasons for any parts failure and
necessity of the repair.

n. Cleanliness and neat, orderly work area makes

job easier to do.

0.

Use proper meters and gauges. Observe

if

cy1 i nder req u i res boring , cranks haft needs
grinding, or if other major shop work is

necessary.

pump.

Assembly (Use Genuine Onan Parts):

1.

2.

3.

Engine assembly procedure is normally the

reverse of disassembly

-

observing proper

clearances of bearings, connecting rod, proper

fitting and sizing of piston, rings, etc.

Follow

proper recommended procedure for

fit

of
valves, adjusting clearances, and torque of all
special items. Use a torque wrench to assure
proper tightness without danger of stripping
threads.

As each internal engine part is assembled, use

crank (or wrench) to rotate crankshaft, making
certain

it

turns freely. If tightness is noted after
any operation you then know your last step is
responsible.

4.

As

each internal engine part is assembled, coat it
heavily with oil (same grade used in crankcase).
During first few critical moments of operation, the

engine will depend on this lubrication.

5.

Xferyou have infernalengi'ne

pzrfs

EiGembTed,

the engine should crank freely.

If

reasonable care
and attention has been given, the engine will
operate efficiently.

6.

At this point, it is a matter of mechanically adding

outside accessory items to the block assembly.

Order

of

assembly

is

reverse

of

disassembly.

7.

When engine is complete, install controls. Check

the tagged wires. Using wiring diagram to con-

nect leads to control, and from control to engine.
All wires are marked for correct identification. If
the unit is to work properly, wires must be

connected correctly.

8,

The engine is now ready for testing. Follow

suggestions given on

Testing and Adjusting

Engines.

Before final test and adjustments, run

the engine about 15 minutes under light load to

reach normal operating temperature.

ASSEMBLY SUGGESTIONS (Things

to

keep in mind during engine assembly)

1. See Onan

Tool

Catalog (900-0019) - many items

require a

special tool

for correct installation.

Some of these tools are:
a. Oil seal driver and guide, bearing driver.

b.

Valve spring compressor, valve lock replacer,

valve guide driver, and valve seat remover.
c. Gear puller and gear puller rings.
d. Piston ring spreader and compressor.
e. Flywheel puller, pry bar, armature puller.

f.

Torque wrench, plastigauge (for correct bear-

g. Load test panel, armature growler, gas

2.

Wet holes in crankcase (holes through
crankcase) -always use copper (gasket) washers.

3.

Nuts, bolts and screws that do not require exact
torque should be tightened snugly, then 1/4extra
turn.

4.

Select proper length of any screw or bolt and

position in hole. Make sure they do not

bottom.

5.

Gasket kits sometimes cover more than one
engine. Therefore, select gasket of correct size
and shape for part being used. Always use new
gaskets.

ing clearance).
pressure gauge (or manometer).

42

6.

When disassembling engine,

mike

bearing plate

gasket thickness. Then select proper shim

thickness for correct end play.

Shims establish end play. Only one thickness gasket is
included in kit.

7.

When assembling crankshaft, make sure bearing
thrust washers are in proper position supported
by bearing stop pins. Use cup grease to hold in

-

place.

8.

When adjusting valve lash, tap rocker arm

so

it is

9.

Crank gears are easier to remove and install if

straight when checking with feeler gauge.

heated a slight amount.

Do

not overheat or temper may be lost

and shaft may expand.

10.

See

FUEL SYSTEM

section for correct engine

time for specific model.

11.

Allow some gear lash (approximately 0.005-inch)

in oil pump.

Do

not install gears tightly against

each other!

TESTING AND ADJUSTING ENGINES

Preparation

Check the following:

1.

Put

proper oil in crankcase.

2.

Service air cleaner.

3.

Connect fuel line.

4. Connect load.

5.

Connect fully charged battery.

6.

Check ventilation for proper cooling.

OPERATION

1.

Start engine.

2.

Check o.il pressure.

3.

Run unit

15

minutes to bring up to operating

temperature.

'

4. Check for oil leaks, loose electrical connections,
tight fuel lines and tight exhaust connections.

ADJUSTMENTS

Adjust governor for speed and sensitivity.

IMPORTANT:

For complete customer satisfaction, repaint unit

(Onan Green, spray can 525-0137, or Onan White, spray can 525-

0216) and apply instructions from Kit

98-11OOC

or Marine Kit

98-

1807.

CYLINDER HEADS, VALVES

Each cast iron cylinder head assembly has alloy
hard en ed-f aced valves,

re1

ease-ty pe rotato rs , al I oy
hardened inserts, guides, rocker arms, injection
nozzles and glow plugs. The push rods run through

'

shields.

Maintenance:

Check the valve clearances at regular intervals (see

SERVICE AND MAINTENANCE

section).

In

addition,

clean the combustion chambers and valve seats at

regular intervals.

VALVE CLEARANCE ADJUSTMENTS

The valves are adjusted cold. Afterthecooling period,

adjust

No.

1

cylinder first and the rest in the firing

order.

RDJE Engines

To

adjust valve clearance, on

RDJE

engines, proceed

as follows:

1.

Rotate flywheel clockwise until cylinder number
is up on acompression strokeand theTC markon
the flywheel lines up with the timing pointer on
the gear cover, then turn

10-45"

past TC to be
sure lifter moves off ramp of cam. Adjust both
valves, intake and exhaust, to

0.017

inch

(0.43

mm).

In this position, both valves will be closed and the rocker

arms

are free to move slightly indicating maximum clearance.

EXHAUST

VALVES

I\

0.017"

(0.43

rnm)

AOJUST

VALVE

CLEARANCE

HE

VALVE

SEAT

FIGURE

51.

SETTING VALVE CLEARANCES

43

2.

3.

4.

*

Using a feeler gauge, check clearance between
rocker arm and valve (see Figure 51). Increase or
reduce clearance until proper gap is established;
adjust with lock nut which secures rocker arm to
cylinder head.

Repeat Step

1

for number 2 cylinder.

Repeat Step 2 for number 2 cylinder.

Compression readings will deviate considerably from
the above readings because of differences in crank­ing speed, altitude and ambient temperature con­ditions. Therefore the specification is given only as a
guide. The best indication of leakage is the pressure
difference between cylinders or a compression

in-

crease when oil is added to the cylinder.

Disassembly:

RDJEA Engines

To

adjust valve clearance on RDJEA engines,

proceed as follows:

1.

Rotate flywheel clockwise until cylinder number 1
is up on a compression stroke and the TC mark on

the flywheel lines up with the timing pointer on

the gear cover, then turn 10 to

45"

past TC to be

sure lifter moves off ramp of cam. Adjust bbth

valves, intake and exhaust, to 0.017 inch

(0.43

mm).

In this position, both valves will be closed and the rocker arm

is

free

to

move slightly indicating maximum clearance.

2. Using a feeler gauge. check clearance between
rocker arm and valve (see Figure 51). Increase

or

reduce clearance until proper gap is established;
adjust with lock nut which secures rocker arm to
cylinder head, Figure 51.

3. To adjust valve clearance for number 2 cylinder,
turn flywheel in aclockwisedirection 180degrees

(1/2 revolution) from position used in Step

1.

The

flywheel position should be between 10 degrees

and 45 degrees past the bottom center

(BC).

4. After timing number 2 cylinder, adjust valve
clearance according to Step 2.

Testing:

The cylinder compression test can be used to deter-

mine the condition of valves, pistons, piston rings and
cylinders.

To check compression, run the engine until
thoroughly warm. Stop engine and remove all injec-

tion nozzles. Insert the compression gauge in one

nozzle hole. Crank the engine and note the reading.

To check for piston blow-by, squirt a small amount of

SAE

50

oil into the cylinder and repeat the check. An

increase

in

compression with oil

in

the cylinder

indicates piston blow-by.

Keep rocker arms, rocker arm nuts, push rods and tappetsin order,

so

they go back in the same valve train position.

1.

Remove rocker box cover, fuel nozzles and

connecting

oil

lines to cylinder heads.

2. Remove intake and exhaust manifold.

3. Remove cap screws holding each cylinder head
to cylinder block.

4.

Remove each head. If it sticks, rap it sharply with a
soft hammer. Do not use a pry.

5.

Remove rocker arms and push rods.

6. Using avalve spring compressor, disassemble the
valve assemblies.

Repair:

Thoroughly clean all components of the cylinder
head assemblies. Remove all the carbon deposits
from the intake and exhaust ports and clean all gasket
surfaces.

Valves:

Remove all carbon and check each valve for

burning, pitting,

or

a warped stem. Refinish valves

that are slightly pitted

or

burned on an accurate valve
grinder. Refinish intake valves to a 42 degree angle
and exhaust valves to a 45 degree angle. If they are
badly pitted

or

have a thin edge when refacing,

replace them.

Check refinished valves for a tight seat to the valve
seat with an air-pressure-type, testing tool

or

by

applying Prussian Blue on the valve face and rotating

it

against the seat.

Valve Guides:

Check valve guide to valve clearance.

See the

DIMENSIONS AND CLEARANCES

section. If

the proper clearances cannot be obtained by replac-

ing the valves, replace the valve guides. Drive the old
valve guides into the valve chambers. Drive new

guides in until they protrude 11/32 inch (8.731 mm)

from the rocker box side of the head. Ream the new

valve guide to obtain the proper clearance.

Valve Seats:

If thevalve seats are pitted, refinish them.

Using conventional seat-grinding equipment, reface

Compression of a standard new engine cranking at each seat to a45degreeangleand aseatwidthof 3/64
about 300 rpm is about 350-4OOpsi (2415 to inch to 1/16 inch (1.191 to 1.588 mm) You should be

2760

kPa). Compression should be fairly uniform, able to reface each seat several times before it

normally with less than 10 psi

(69

kPa) difference

becomes necessary to replace

it.

between the highest and lowest cylinder, taken at the

same cranking rpm. Excessively high readings

in-

If the valve seats are loose

or

cannot be refaced,

dicate carboned combustion chambers.

replace them.

44

Use Onan tool number 420-0272

in

a drill press

(Figure 52) to remove each valve seat. Adjust the tool

to cut 1/64 inch (0.397 mm) from the edge of theseat.
Oil the pilot to prevent

it

from seizing in the valve
guide. Cut each seat down to a narrow rind on edges
and bottom and break

it

out with a sharp tool. Be

careful not to cut into the counterbore bottom.

DRILL

PRESS

BE

SURE

TO

OIL PILOT OF

TOOL

AFTER CUTTING

RIND

IS

EASILY

REMOVED.

I

MAKE CUT

FROM

EDGE

OF

FIGURE

52.

REMOVING VALVE SEATS

Thoroughly clean the valve seat counterbore and

remove any burrs from the edges. If the counterbore

is damaged,

it

will have to be machined for an oversize

seat. Oversize seats are available

in

0.002

inch,

0.005

inch,

0.010

inch and 0.025 inch

(0.58,0.056,0.068,

and

0.09

mm). Otherwise, install new standard size seat

inserts.
Drive the new valve seat inserts into place. Be certain

that each seat rests solidly on the bottom of the
counterbore at all points. To make installation easier,
heatthecylinderhead in anovenat325'F (162"C)for
about 1/2 hour and cool the valve seats in dry ice.

Face each new seat to a 45 degree angle and a width
of approximately 3/64 inch (1.191 mm). The finished
seat face should contact the approximate center of

thevalve face. Use Prussian Blueon each valve face to

check this. Make any corrections on the seat, notlhe
valve face.

When the new seats are installed and faced, insertthe
valve into each, and check the clearance from the
valve head to the face of the cylinder head. This must

be at least

0.030

inch (0.762 mm).

If

it is not, regrind

the seat.

Valve

Springs:

Check thevalvesprings on an accurate

compression scale. Valve spring data is given in the

DIMENSIONS AND CLEARANCES

section. Replace
any spring that is weak, cracked orpitted, orhas ends
ou t-of-square.

CYLINDER HEAD GASKET SEALANT

The cylinder head gaskets on 2-,cylinder, water­cooled RDJ series diesel engines require a Room
Temperature Vulcanizing

(RTV)

Sealant around the
water passages between the gasket, head, and block
whenever the head gaskets are replaced. The RTV

sealant must be used along with each new head
gasket.

Onan recommends the White RTV Sealants such as:

Dow-Corning Silastic RTV Silicone Rubber
General Electric White RTV Sealant

Adhesive #732

Application

Apply sealant bead .03-.06 inches thick at six places
on both sides of the head gasket according to
dimensions shown in Figure 53. The sealant may also
be applied to the finished surfaceof the block and/or
head to just one side of the gasket.

The gasket must be installed before the

RTV

KZx

Sealant hardens (within one half hour).

Do

not useexcessivesealantas it couldsqueezeinto thecored holesor
into the piston compression chamber and affect valve operation.

One

hour

is the minimum cure time before operating
the engine. Water and water vapor accelerate the
curing time of the RTV sealant

so

wateror coolant can
be added to the engine after the head bolts are
torqued to specifications. Engine heat completes the
curing process.

Installation:

1. Push a valve seat stem oil seal onto each intake
valve guide and clamp in place. Then oil inside
surface of each seal.

2. Oil stem

of

each valve lightly and insert each in its

own guide.

3.

Check each valve for a tight seat with an air-

pressure type tester.

If

a tester is not available,
make pencil marks at intervals on valve face;
observe if marks rub off uniformly when valve is
rotated part of a turn in seat. If seat is not tight,
regrind valves.

4. Using a valve spring compressor, compress each
valve spring and insert valve spring retainer and
retainer locks.

5.

Install head assembly and gasket to cylinder
block. Tighten head bolts to 44 to 46 foot-pounds
(60-62 Nom). Follow sequence in Figure 54 and

Steps a. through c.

45

P

4

PLACES,

BOTH

SIDES

SEE NOTE

I

P

DASHED LINES INDICATE CORED
HOLES, RTV BEAD MUST

BE

OUTSIDE

THIS AREA

FIGURE

53.

HEAD GASKET-RTV SEALANT APPLICATION

d. Tighten cylinder head bolts in same sequence

to 44-46 foot-pounds (60-62 Nom).

e. After 60 seconds, retighten cylinder head bolts

in

sequence to 44-46 foot-pounds (60-62
Nom). This step compensates for the com­press of the cylinder gasket.

6.

Install intake manifold, nozzles, glow plugs and

7.

Install valve stem cap.

8.

Install push rods, rocker arms and rocker arm

9.

Set valve clearance. See Figure

51.

oil

lines.

.

nuts.

CAUT,ON

After the first

50

hours

of

operation,

Exz3

retighten the cylinder head bolts and

check valve clearance or the head gaskets may

be

blown out.

FIGURE

54.

HEAD BOLT TORQUE SEQUENCE

Use Never-Seez, Fel-Pro

C5-A

or equivalent thread lubricant

when installing cylinder head bolts.

INTERNAL DISASSEMBLY

a.

Tighten cylinder head bolts finger-tight.

If engine disassembly is necessary, observe the
following order (Le. Flywheel, Gear Cover..

.).

As

b. Install exhaust manifold.

c.

Tighten

disassembly progresses, the order may be changed
somewhat as will be self-evident. The engine

assembly procedure

is

the reverse

of

disassembly.
Any special assembly instructions for a particular
group are included in the applicable section, When
reassembling, check each section for these special
assembly instructions or procedures.

head

bolts

in

sequence

shown

in

Figure

54

to

25-30

foot-pounds

(34-

41 Nom).

46

FLYWHEEL

The flywheel is a tapered fit on the crankshaft.

Improvise a puller, using at least a 7/16-inch bar

(11.113 mm), and drill two 7/16-inch (11.113 mm)
holes 2-7/8 inches (73.025 mm) between centers.
Loosen the flywheel mounting screw a few turns.
Place bar against the flywheel screw and attach bar,
using two 3/8-16 thread screws

in

the holes provided
in flywheel. Alternately tighten the screws until
flywheel is free.

FLYWHEEL REPLACEMENT

Replacement flywheels are supplied without the
timing markings because each flywheel must befitted
to

its engine. The only accurate method of determing

the top dead center (TDC) and port closing points is

to

measure the piston travel. This is a critical

measurement and should be attempted only with

accurate, dependable equipment.

With the flywheel mounted, remove the head and
install a depth gauge over the front piston. Rotate the
flywheel to find the TDC position on the compression
stroke and mark this point on the flywheel. Next, turn
the flywheel counterclockwise

until

the piston drops
exactly 0.128 inch (3.25 mm). Mark both TDC and
piston drop to PC point on the flywheel.

Ring

Gear:

To

remove the ring gear, if damaged, saw

part way through, then break it using acold chisel and
heavy hammer.

To

install a new ring gear, place

it

in

an oven heated to

380"

F - 400"

F

(192"

to 204"

C)

for 30 to 40 minutes.

Do

not heat with a torch or ring gear may be

warped.

When heated properly, the ring will fall into place on
the flywheel. If it does not go on all the way by itself,

drive

it

into place with a hammer.

Do

itfastand do not
damage the gear teeth. The ring will contract rapidly
and may shrink to the flywheel before

it

is

in

place. If

this occurs, a new ring gear may be required.

GEAR

COVER

To remove the gear cover, detach the uppergovernor

ball joint. Remove thegovernorspeed-adjustment nut

and governor spring bracket.

Remove the screws holding the gear cover to the
crankcase. To loosen the gear cover, tap

it

with a soft

hammer.

Governor

Shaft

The governor shaft is supported by

two sets of needle bearings.

To

remove the shaft,

remove the yoke and pull the shaft from the gear

cover. If the shaft is binding, clean the bearings. If

loose, replace the bearings. To remove the larger

bearing, drive both bearing and oil seal out from the
outside

of

the gear cover. Remove the smaller bearing

with an Easy-Out

or

similar tool. Press new bearings

and oil seal into place. See Figure

55.

GOVERNOR

GOVERNOR ARM

.

GOVERNOR SHAFT

YOKE

(Smooth

side

toward

cup)

FITS

INTO

GOVERNOR

CUP BE

SURE

THAT

OIL

PASSAGES ARE OPEN

I

8343

IF

FEELER

WILL

ENTER HOLE

112"

,

BALL HAS

FALLEN OUT

FIGURE

55.

GEAR

COVER

ASSEMBLY

47

Gear Cover Oil Seal:

Replace the oil seal if damaged
or worn. Drive the oil seal out from inside the gear
cover. Lay the cover on a board

so

the seal boss is
supported. Using an oil seal driver, insertthe new seal
from the inside with rubber lip toward outside of gear
cover (open side of seal inward) and drive it flush with
the outside surface. During gear cover installation,
use the driver to protect the oil seal. See Figure 56.

Assembly, Gear Cover:

1. Work governor shaft to check for binding and see
that the governor shaft end-thrust ball is

in

place,

Figure 55.

2. Turn governor yoke

so

smooth side is toward

governor cup.

3.

Turn gove,rnor cup

so

stop pin in gear cover will fit

into one of the holes in the cup surface (Figure

55). Measure distance from end of stop pin to

mounting face of cover. It should be 25/32 inch

(19.844

mm). If it isnot, replace pin. Pin should be

positioned with open end facing crankshaft seal.

4. Coat oil seal lip with oil or grease. Set a piece of
shim stock over the crankshaft keyway to protect
seal and install gear cover. Tighten mounting
screws

to

15 to 20 foot-pounds (20 to 27 Nom).
Before tightening screws, be sure the stop pin is
in governor hole.

GEAR COVER

INSTALL OIL SEAL

FLUSH WITH THIS

SURFACE

'1

FOILSEAL

.. ,...

THIS SURFACE MUST

'.::$>

k..fl

BE CLEAN BEFORE

INSTALLING

SEAL

'

FIGURE

56.

GEAR COVER

OIL

SEAL

GOVERNOR

CUP

To

remove the governor cup, remove the snap ring

from the camshaft center

pin

and slide the cupoff. Be
sure to catch the five flyballs that will fall out when the
cup is removed. Figure

57

shows the governor cup.

WHEN GOVERNOR

IS

CAM

SHAFT

CENTER PIN

GOVERNOR CUP

GOVERNOR FLY

BAL

FIGURE

57.

GOVERNOR CUP

Repair:

Replace any flyballs that have flat spots or
grooves. Replace the cup if the race surface is
grooved or rough. The governor cup must be a free
spinning fit on the camshaft center pin, but should be

replaced if excessively loose or wobbly.
Check the distance the center pin extends from the

camshaft gear; this distance must be 25/32 inch

(19.844 mm) to give the propertravel distance for the
cup.

If

it is less, the engine may race; if more, the cup

will not hold the balls properly. If the distance is too

great, drive or press the center pin in. If it is too small,
replace the pin; it cannot be removed withoutdamag­ing the surface. In some cases, if the distance is too
small, the head of the governor cup can be ground to
give the necessary 7/32 inch (5.556 mm) travel dis­tance.

Installation:

To

install the governor assembly, tip the
front of the unit upward. Set the flyballs in their
recesses and position the governor cup on its shaft.
Finally, brush with heavy grease and install the snap
ring on the center pin.

PISTONS,

RINGS,

CONNECTING RODS

Onan diesel engines use cam-ground aluminum
pistons. Each piston is tapered and fitted with three
compression rings and an oil control ring. Full­floating piston pins connect the piston to its connec-

ting rod. The pins are held

in

place with a snap ring at
each end. The lower end of each connecting rod
contains half-shell precision bearings and the upper
end

,

semi -f

i

n

ish ed bushings.

Some engines are fitted with 0.005 inch (0.127 mm) oversize
plstons

at

the factory. These engines are marked with an E
following the engine serial number. Use 0.005 inch (0.127 mm)
oversize rings for these pistons.

48

'

Removal and Disassembly

On 2-cylinder engines, the connecting rod and cap
are stamped for installation

in

the proper cylinder.
When removing piston assemblies, check the mark­ing

so

each can be installed in the proper cylinder.

1.

Drain crankcase oil and remove oil base.

2. Remove cylinder heads.

3.

Before pushing pistons out, scrape carbon at top

,

of cylinder bore.

4. Remove cap from each connecting rod and push
assembly through top of cylinder bore. Replace
cap and bearing inserts in proper assembly.

5.

Using a ring expander, remove rings from each
pis ton.

6. Remove two retaining rings and push piston pin
from each piston.

Cylinders

The cylinder walls should be free of scratches, pitting
and scuffing. Check each with an inside reading

micrometer for out-of-round and wear. The bore

should measure between

3.4995

inches

(88.8873

mm)

and

3.5005

inches

(88.9127

mm) and be less than

0.001

inch

(0.0243

mm) out-of-round.

If necessary, rebore the cylinder

to

fit the next
available oversize piston. Pistons and rings are
available in

0.005

inch

(0.127

mm),

0.010

inch

(2.540

mm),

0.020

inch

(0.508

mm)

0.030

inch

(0.762

mm) and

0.040

inch

(1.016

mm) oversize. If the
cylinders do not need refinishing, remove any ex­isting ridges from the top of the walls with a finestone.

Pistons:

Clean thoroughly and inspect each piston. Clean the
carbon from the ring grooves and besure all oil holes
are open.

If

any piston

is

badly scored or burred, loose
in the cylinder, has badly worn ring grooves or
otherwise

is

not in good condition, replace it. See

Figure 58.

m

positions.

Check the clearances

90

degrees from the axis of the
piston pin and below the oil control ring. Clearance
should be

0.005

inch - 0.0070 inch (0.127 to

0.178 mm).

If

not, replace the piston and check the

'

cylinder for possible reconditioning.

PISTON PINS

Each piston pin should be a thumb push fit into its
piston at room temperatures. If the pin is excessively
loose, install a new one. If the condition is not
corrected, install the next oversize pin. If the piston is
worn enough

so

that the oversize pin will not fit,

replace it.

RINGS

Inspect each ring carefullyforfit in the piston grooves

Install pistons with valve relief recess facing
the camshaft side of engine

to

match valve

CAUTION

~

.-

IN

POSITION

CAST

IRON

OIL CONTROL

INSTALL WlTH

VENTS AT BOTTOM

(AWAY

FROM

CLOSED

END

OF

PISTON)

RINGS PISTON

CHROME BEVEL

COMPRESSION

RECESS

-1

AB87

'

'

VENTS

FIGURE

58.

PISTON

RINGS

and seating on the cylinder wall. Fit each ring

to

the
cylinder wall at the bottom of its travel, using a piston
to square the ring

in

the bore. Check the gap with a

feeler gauge.

It

should be

0.010

inch to

0.020

inch

(0.254 to 0.0508 mm).

If

the gap is too small, file the
butt ends of the rings. Do not use rings that need a lot
of filing. They will not seat right on the cylinder walls.

If

oversize pistons are used, use the correct oversize

rings.

CONNECTING

RODS

Clean the connecting rods and check each for
defects. Check the connecting rod bushings for
proper clearance with the piston pin. Clearance
should be 0.0002 inch to 0.0007 inch

(0.0051

to

0.0178 mm).

If

the bushings are excessively worn, press them out

and install one new bushing from each side of the

bushing bore. Press the new bushings only until flush

with the sides of the rod to leave 1/16 inch to 7/64 inch

(1.588 to 2.776 mm) oil groove in the center. See

Figure

59.

CONNECTING

ROD

BEARINGS

Inspect the connecting rod bearingsfor burrs, breaks,

pitts and wear. Measure the clearance between

bearings and the crankshaft journal. The clearance

should be

0.001

inch to

0.003

inch

(0.025

to

0.076 mm).

If

necessary, replace with new standard

or

oversize precision bearings.

49

CONNECTING ROD

BUSHING ENDS

M

BE FLUSH WITH

S

OF

ROD TO PER

1/16”01L GROOVE

BETWEEN BUSHINGS

II

Iiil

F

’RECISION TYPE

BEARING

’

MEASURE CLEP

DIRECTION INDl

ARROW

A881

Rev.

rR

IC

LANCE
:ATED

3SS-S

ECTl ON

IN
BY

FIGURE

‘59.

CONNECTING

ROD

BUSHINGS

ASSEMBLY AND INSTALLATION

1.

2.

3.

4.

5.

6.

7.

8.

9.

Install connecting rods on each piston with pins
and retaining rings. If new bushings were in­stalled, check to see that ends are flush with
connecting rod to provide for oil recess

in

center.

Install all

rings on each piston. Tapered-type

rings will be marked

top

or identified in some
other manner. Place this mark toward closed end
of piston. Space ring gaps

1/4

of way around

piston from one another.

No

gap should be in line

with the piston pin.
Position a bearing half

in

each connecting rod. Be
sure there is no dirt under bearing. This could
cause

high

spots and early bearing failure.

Oil cylinder walls. Install each piston in proper

cylinder using a suitable installer. Each assembly
should be installed with stamp on piston facing
same direction as when removed.

Position each connecting rod on crankshaft, oil
the journal, and install its rod cap with bearing

half. When installing rod cap, position

so

raised

witness mark on forging matches mark on con-

necting rod. See Figure

60.

Tighten cap screws to specified torque.
Crank engine over by hand to see that all bearings

are free.
Install oil base with a new gasket.
Install cylinder heads using proper bolt tighten-

ing sequence.

10.

Replace oil.

CAMSHAFT

The camshaft is a one-piece machine casting, driven

through gears by the crankshaft.

It

rides on sleeve

bearings pressed into the crankcase.

In

addition to providing a means of opening and

closing the valves, the camshaft operates the injec-

tion pump and fuel transfer pump.

FIGURE 60. CONNECTING

ROD

CAP

Removal:

1.

Remove rocker arms and push rods from valve

chambers.

2.

Remove injection pump and fuel transfer pump

from engine.

3.

Remove crankshaft gear retaining washer by

removing lock ring on crankshaft.

4. Lay engine on its side to avoid dropping tappets
and remove camshaft assembly as a group.

If.

necessary, pry it out with a screwdriver between
camshaft gear and crankcase.

5.

Remove valve tappets. These can be removed
only from the camshaft end of the push rod holes.

Repair:

If a lobe has become slightly scored, dress it
smooth with afinestone. If the camshaft is badly worn
or scored, replace it. After installing a new camshaft,
retime the injection pump to the engine.

Camshaft Gear:

This gear is a pressed fit on the

camshaft and drives it at

1/2

the crankshaft speed.To

remove the gear, use a hollow tool or pipe that will fit
inside the gear bore and over the center pin. Press the
camshaft out of the gear bore. Be careful not to
damage the center pin.

Camshaft Bearings:

Thecamshaft bearings should be

replaced if the clearance to the camshaft is greater
than specified, the bearings show cracks, breaks,

burrs

,

excessive wear, or other defects. The

camshaft-to-bearing clearance should be

0.001

2

inch

to

0.0037

inch (0.0304 to

0.0938

mm).

To

check the

rear bearing, remove the expansion plug at the rear of
the crankcase.

50

PRESS BEARING

FLUSH WITH

BOn-OM OF

RECESS

REAR

EARING

BEARING

.9-3

1/32

2

1/16

FIGURE

61.

CAMSHAFT

BEARINGS

ANKSHAFT WASHER

FIGURE

62.

CAMSHAFT

ENDPLAY

2-1/4 x 20

PULLER

PRESS BEARING

FLUSH WITH

FRONT CRANK-

CASE

SURFACE

-

ALIGN OIL

HOLES

FRONT

8

EA

RI

N

G

Press new bearings into place, Figure 61. Press the
rear bearing flush with the bottom of the expansion
plug recess. Press the front bearing in flush with the
crankcase front surface

so

the oil passages are

aligned.

Do

not attempt to ream the bearings as they
are a precision type. Afterthe rear bearing is installed,
insert a new expansion plug in the recess, using
sealing compound, and expand it into place with
sharp blows at

its

center.

Installation, Camshaft

Assembly:

1.

Install key and press camshaft gear on camshaft
until

it.

bottoms on flange with no clearance.

2.

Install governor components.

3.

Slide thrust washer onto shaft. Measure camshaft
end play: it should be

0.007

inch to

0.039

inch

(0.178 to

0.991

mm). See Figure

62.

4.

Lay engine on its side

or

end and insert push rod

tappets.

5.

Install camshaft assembly in engine. Align timing

marks on camshaft gear and crankshaft gear. See
Figure

63.

6.

Replace push

rods

and fuel transfer pump.

7. When engine

is

reassembled, install injection

pump following the steps for Injection

Pump

Installation in the

FUEL

SYSTEM

section. This

step is critical.

CRANKSHAFT

Onan diesel engines use a counter-balanced, ductile
iron crankshaft.

To

increasetheshaftfatigue durabili­ty, all crankpin fillets are shot-peened during
manufacture.

FIGURE

63.

TIMING

MARKS

51

FIGURE

64.

REMOVING CAMSHAFT GEAR

Removal

1.

2.

3.

4.

5.

6.

Remove lock ring and retaining washer in front of
crankshaft gear.

Pull off crankshaft gear. It has 2-1/4-20 UNC
tapped holesfor attaching agear pulling ring. Use
care not to damage teeth if the gear is to be

reused. See Figure 64.

Remove oil pan, pistons and connecting rods.

Remove bearing cap from center main bearing.

Remove rear bearing plate from crankcase.

Remove crankshaft through rear opening

in

crankcase. Catch upper half of center main

bearing support as

it

slides off its mounting

surface.

Inspection:

Clean the crankshaft and blow out all oil
passages. Check journals for out-of-round, taper,
grooving or ridges. Pay particular attention to ridges
orgrooveson eitherside of theoil holeareas. Unusual
conditions here often point to previous neglect of oil
changes.

.

If journal dimensions are not within limits, or the

journals are scored, regrind the crankshaft.

Crankshaft Grinding:

Crankshaft grinding requires a

trained, experienced operator working with precision

equipment. Procedures which may besatisfactory for

some spark-ignition engines may well be unsatisfac­tory for diesel applications, resulting in expensive
failures. Onan emphasizes that if facilities or trained

personnel are not available, the crankshaft may be

sent to the factory.

Special procedures must be observed when rework-

ing diesel crankshafts.

In

addition to machining, the
crankshaft must be shot-peened and super-finished.
Failure to

shot-peen

the crankpin fillets is likely to

cause early failure. When the shaft is machined,

follow this data and Figure

65

to shotpeen each crank

pin fillet.

3/16’’

(4.763

mrn)

~\HEs~

TO

BE

SHOT- SURFACES PEENA

II

I

L!z&ZZ~J.%

,TO

EE

MASKED

-

._.

.-

1

I

THIS

AREA

DURING

SHOT-

PEENINU

OPERATION

U

FIGURE

65.

SHOT-PEENING THE CRANKSHAFT

1. Almen gauge reading 0.012-A

(0.305).

2. Peen with 0.019 inch (0.482 mm) diameter cast

3.

Peen for

30

seconds on each crankpin fillet.

4. Mask off connecting rod bearing areas.

steel shot.

Undersize bearings and connecting rodsare available

to rework the shaft to 0.010inch (0.254 mm), 0.020

inch (0.508 mm), and

0.030

inch (0.762 mm) under-

size.

Main Bearings:

Replace main bearings if clearances
are greater than limits or if the bearings are worn,
grooved, or broken.

Precision replacement inserts and thrust washers are
available for all main bearings.

Do

not ream the

bearings.

Align the oil holes and press the new bearings into the
front and rear housings.

Rear

Oil

Seal:

The rear oil seal is in the rear bearing
plate. If damaged, drive it out from the inside of the
plate. Using the oil seal installing tool, install a new

seal with the rubber lip facing outward (open side of
seal inward). See Figure 66. Drive the new seal flush
with the rear surface of the bearing plate. Leave the
seal installer on during bearing plate installation to

protect the oil seal.

Installation:

After each installation step, check the

crankshaft to be sure it is not frozen into place.

1.

Press front and rear main bearings into place,
align bearing and bearing housing oil holes. Do
not attempt to drive a bearing into a cold block or
rear bearing plate.

2. Install thrust washers and locking pins.

3.

Oil bearing surfaces and install crankshaft from

rear of crankcase through rear bearing plate hole.

52

4.

Mount and secure rear bearing plate.

5.

Heat timing gear on an electric burner

or

oven to

about 350"

F

(175°C). Install key on crankshaft,
then drivegear into place. Install retaining washer
and lock ring.

CRANKCASE

If the crankcase requires replacement, a new set of
injection pump shims will be furnished with the new
crankcase. These must be used and, in addition, the
injection pump must be retimed to the engine.

6-

Check crankshaft end play. Use enough rear
bearing plate shims and gaskets

to

provide 0.010

inch

(0*254

mm)

to

0'015

inch

(0*381

mm)

end

'lay'

If

gaskets

Of

more

than

0'01

inch

steel

shim

Of

proper

thickness

and a thin

gasket

on each side

of

shim. This avoids excessive

gasket compression and maintains bolt torque.

BREAK-IN

PERIOD

Whenever new rings or pistons are installed or the
cylinder refinished, the engine must be run-in before

regular operation can be resumed. Run theengine for
load, and 2 to 3 hours at 2/3 load. Regular operation

can

then

be

Avoid

light

load

operation

during the following several hours for best ring

(0.381

mm)

total

thickness

are

required,

use

a

15

to 20 minutes at no load, about 30 minutes at 1/3

7.

Install

piston assemblies.

seating to prevent oil consumption.

USH

DE

THRUST

WASHER

ALIGN

OIL

HOLES

MAIN BEARING

LIP

FACING

MUST

BE

FLUSH

WITH

FIGURE

66.

MAIN BEARING INSTALLATION

53

CONTROL

SYSTEM

Due to the widevariety of uses to which these engines
are adapted, operating controls are not supplied with

the engines. In most cases, the engines are used for

prime power to operate other manufacturers equip­ment. Installation nearly always differs. Therefore,
the manufacturer

or

fabricator generally provides a

control for the complete unit.

MAINTENANCE

Periodically check all connections and contacts

in

the

control system to be sure they are tight and clean.

PRE-HEAT SWITCH

I

A*

SI

I

SWITCH

I

NO.

12

WIRE

GLOW PLUGS

FUEL SOLENOID

*

s2

FUEL SOLENOID

SWITCH

I

WIRING

DIAGRAM

STARTER

81

----

*I

+CUSTOMER SUPPLIED

,

SCHEMATIC

TYPICAL STANDARD ENGINE

54

Onan Corporation
1400 73rd Avenue

N.

E.

Minneapolis,

MN

55432

Telex: 275477
Fax: [phone]

Onan

is

a registered trademark

of

Onan Corporation

61 2-574-5000