The Groundsmaster 300 series mower is a medium size, maneuverable, commercial rotary with over twenty
years of mowing experience. During those years its design has been continuously improved for optimum
productivity and durability.
GM 345
Features
1. Ford 4 cylinder gas engine (45hp).
2. Sunstrand series M15 inline variable speed hydrostatic drive.
3. Hydraulic power steering and lift functions
4. Available in 2wd.
GM 325-D
Features
1. Mitsubishi 3 cylinder diesel engine (25hp).
2. Sunstrand series M15 inline variable speed hydrostatic drive.
In this section we will look at some troubleshooting procedures for the Ford Gas Engine.
Engine Identification
The engine is identified with a decal affixed to the left side of the valve cover.
The decal contains the engine serial number.
The model number and displacement. ( i.e. 411 = 4 cyl 1.1 liter)
The special options (S.O.) number.
The engine is also stamped on the left rear top edge of the block.
This stamping includes:
A - Serial number.
B - Engine Code.
C - Engine build code: (Example 4K26)
• The first number indicates the year.
• The letter indicates the month in alphabetical sequence. ( A January, B February, etc.)
• The last two numbers are the day of the month.
Complaint: Low engine power
Affect:
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1. Poor cutting unit performance.
2. Poor hill climbing ability.
3. Slow hydraulic response.
4. Slow throttle response.
5. Rough running engine.
Cause:
1. Incorrect engine idle settings.5. Cracked or bad spark plugs.
2. Misadjusted carburetor linkage.6. Cracked or broken plug wires.
3. Governor adjustments.7. Plugged or restricted air filter.
The final adjustments are made with the engine running. To guard against
possible personal injury, engage the parking brake and keep hands, feet, face
and other parts of the body away from the fan or other moving parts.
Low Idle Adjustment.
1. Start the engine and move the throttle to the slow position.
2. Manually rotate the throttle arm closed until it contacts the stop.
3. Check the idle speed and adjust carburetor idle speed screw, if necessary to attain 1350 ± 50 rpm.
• This prevents the throttle plate from being able to bottom out in the carburetor barrel.
4. Release the throttle arm, loosen the jam nut on the governor low idle speed screw and adjust it to attain
1500 ± 100 rpm.
1. Slowly move the throttle to the FAST position until the engine reaches 3200 ± 100. Shut off the engine.
Adjust the high speed adjustment screw until it contacts the speed control lever.
IMPORTANT: Do not overspeed the engine because transmission damaged could occur.
2. If 3200 rpm can not be attained, check the throttle cable adjustment.
• The governor arm must not contact the cable cover when the unit is at high idle.
• If the governor arm contacts the cable, loosen the retaining bolt and move the cable.
3. If the throttle lever on the instrument panel will not stay in the fast position, remove the panel cover and
tighten the nut and capscrew at the base of the throttle lever.
1. Move the throttle rapidly from SLOW to FAST. The engine should not surge, if the engine surges proceed to
step 2.
2. Check the V-belts from the engine to the governor pulley and assure that they are tight.
• The belt is adjusted to 45 lbs of tension on a belt gauge for a new belt.
• A used belt is re-tensioned to 28 lbs.
• The replacement belt PN is 67-8510.
3. Loosen the jam nut that retains the anti-surge screw. Rotate the screw clockwise 1/8 of a turn at a time until
the surging stops.
4. Check the low and high idle speed to be sure that there is no change in the initial settings. If the idle speed
has increased, the anti-surge screw has been turned in too far and it must be backed out.
Other things to check when engine surges:
A. Carburetor too rich or lean.
B. Binding in the throttle linkage.
C. Governor worn internally.
Governor Spread or Sensitivity Adjustment.
Governor spread is the difference between the no load governed speed, and the full load speed.
For the governor to work correctly this spread should be 5 to 10 percent.
To check governor spread, check and record the no-load high idle speed and compare this to the loaded high
idle speed.
To increase the spread adjust the adjustment bolt to position the spring farther away from the lever hub. To
decrease the spread position the spring closer to the hub.
The cylinder leakage test can locate the following problems:
1. Leaking intake valves.
• Air leaking from carburetor.
2. Leaking exhaust valves.
• Air leaking from muffler.
3. Leaking cylinder head gaskets.
• Air leaking externally by head gasket.
4. Worn piston rings.
• Air leaking from breather or dipstick tube.
NOTE. There will always be some air leakage past the rings. Use the tester gauge to determine the severity of
the leak.
With the engine rotated until the piston is at the top of travel on the compression stroke. The cylinder is filled
with air through the spark plug opening, The leakage tester will display the percentage of air lost when the piston
is at the top part of the compression stroke.
A cylinder leakage of 25 percent or less is acceptable.
Compression Testing.
1. Make sure the batteries are fully charged.
2. Remove all the spark plugs.
3. Set the throttle to high idle and the choke in the wide open position.
4. Install an automotive type (0-300 PSI) compression gauge.
5. Using an auxiliary starting switch, crank the engine (with the ignition switch off) at least five compression
strokes and record the highest reading.
6. Normal compression should read 170 to 185 PSI depending on engine temperature and cranking speed.
7. Repeat the test on each cylinder.
If one or more cylinders read low, and a cylinder leakage tester is not available, squirt approximately one
tablespoon of engine oil on top of the pistons in the low reading cylinders.
Repeat compression test on these cylinders.
1. If the compression improves considerably, the piston rings are at fault.
2. If the compression does not improve, the valves are sticking or seating poorly.
3. If two adjacent cylinders indicate low compression pressures and squirting oil in the pistons does not
increase the compression, the cause may be a leaking cylinder head gasket between the two cylinders.
In this section we will look at some troubleshooting procedures for the Mitsubishi Diesel Engine.
Engine Identification
The engine model number and serial number is listed on a decal on the valve cover.
The engine serial number is also stamped on the injection pump mounting surface.
The exhaust from a diesel engine can provide information about the running condition of the engine. A normally
operating engine will have exhaust that is clear to a slight brownish/gray color.
A cylinder leakage test may be performed if the test equipment is available.
The leakage test can locate:
1. Leaking intake valve.
• Air leaking from the air filter or intake manifold.
2. Leaking exhaust valve.
• Air leaking from the muffler.
3. Piston rings not sealing properly.
• Air leaking from crankcase breather or dipstick tube.
(NOTE: there will always be some leakage past the rings)
With the engine rotated until the piston is at the top of the travel on the compression stroke. The cylinder is filled
with air through the glow plug opening. The leakage tester will display the percentage of air lost, when the piston
is at the top part of the compression stroke.
A cylinder leakage of 25 percent or less is acceptable.
Compression Testing.
1. Make sure the battery is fully charged.
2. Remove the glow plugs from all three cylinders.
3. Hold the fuel shut off lever in the closed position to stop the fuel delivery during the compression test.
• This will prevent wash-down of the cylinders and inaccurate readings.
4. Crank the engine with the starter motor until you get a stable gauge reading. (4 or 5 pulses)
5. If the pressure is less than 455 psi (32 kg/cm²) it will be necessary to find the cause of the low compression.
6. The difference between cylinders should be no more than 36 psi (2.5 kg/cm²).
IMPORTANT: DO NOT put oil into the combustion chamber before performing a compression test.
Damage may result because of hydraulic forces acting upon the piston and the connecting rod.
The diesel engine requires that the fuel be sprayed into the combustion chamber, at a precise point in the
compression stroke. The point at which this fuel injection occurs is the injection timing. If the nozzle is defective,
damaged, or adjusted incorrectly, the injection timing can be affected. This can cause hard starting, low power
output, excessive smoke or engine knocking.
IMPORTANT: Always use fresh filtered fuel in the nozzle tester. Use of dirty fuel can damage the
precision parts of the injector nozzle.
Injection nozzle tests:
The nozzle tester forces fuel from the nozzle under extremely high pressure.
Always point the nozzle away from your self and any other personnel.
To prevent possible injury always wear safety glasses.
1. Pressure test.
The injection nozzle is connected to the nozzle tester and the nozzle opening (Cracking) pressure is
measured. The pressure at which the injection nozzle opens has a direct effect on the injection timing and
the fuel spray pattern.
The ability of the nozzle to correctly atomize the fuel can be checked by performing a nozzle spray test.Pump the nozzle tester and watch the spray pattern.
• A solid stream or large droplets indicates a faulty nozzle.
• Fuel should be well atomized and in a consistent spray pattern.
The diesel engine requires glow plugs to warm the combustion chamber to assist in starting. Evidence of faulty
glow plugs includes: hard starting, excessive smoke, or engine knocking.
There are several ways to test glowplugs.
The resistance of the glow plug can be measured with an Ohmmeter.
Normal resistance is 2 to 3 ohms.
0 ohms indicates a shorted glow plug.
An O.L. reading on the ohmmeter indicates an open circuit in the glow plug.
Another way to test the glow plugs is to remove the plug and connected it to a battery. If the glow plug ends turn
red, the glow plug is working.
A third test is to measure the amperage draw when the glow plug circuit is energized. The operating circuit
should draw 30 amps. (10 amps per glow plug)
The drive system on the Groundsmaster 300 series consists of a Sunstrand Series 15, inline hydrostatic
pump and motor assembly. This assemble is connected to a Dana GT-20 axle/differential assembly.
Engine power is transmitted from the engine to the input shaft of the hydrostatic unit. The output of the
hydrostatic unit transmits the power to the pinion shaft, through the differential and to the wheels. The units
brakes are fastened to the outer end of the axle.
Hydrostatic Transmission Operation
Charge Circuit
The charge circuit supplies oil to the hydrostatic circuit and replenishes the oil normally lost through internal
leakage and transmission cooling.
1. Oil from the reservoir is drawn through the oil filter to the charge pump.
2. From the charge pump, the oil is exposed to the charge relief valve which maintains a charge pressure of 70
to 150 psi.
3. The oil then flows to the charge check valves.
4. The check valve that is in the low pressure, (non-driving) side opens and allows oil to flow to the drive loop.
The drive circuit consists of a variable displacement pump and the hydrostatic motor.
Drive circuit operation.
1. When the traction pedal is depressed the swash plate in the pump rotates and the pump begins to pump.
2. The oil from the pump flows to the hydrostatic motor.
3. The oil flows through the hydrostatic motor and returns to the pump. (The oil flows in a closed loop).
There is a bypass valve located in the drive circuit. When the unit is pushed with the engine off, this valve allows
the oil being forced out of the hydrostatic motor to be directed back to the motor, instead of being forced through
the pump.
Note: Use the bypass valve to move the unit a short distance only, excessive travel can damage the
internal components of the hydrostatic transmission.
• Remove the test port plug using a 3/16” allen wrench.
• Connect 10,000 psi gauge into the test port using a 3/8 - 24 adapter.
• Chain machine and lock brakes.
• Operate engine at 3200 RPM.
• 2WD, drive pressure should read 4000-4500 psi. (DO NOT exceed 5000 psi)
• 4WD, drive pressure should read 5200 psi.
Low drive pressure. (Charge pressure “OK”)
2. Possible causes.
• Leaking check valves.
• Leaking acceleration valves.
• Leaking bypass valve. (tow valve)
• Worn drive pump.
• Worn drive motor.
3. Performance results.
• Noisy operation. (Oil leaking past check valves or acceleration valves)
• Poor hill climbing performance. (Slows or stops on hills)
• Complete drive failure.(Unit stops moving)
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Relief Valve
The 4 wheel drive unit has an externally mounted relief valve. To check the relief valve setting, the test gauge
must be connected to the forward test port on the bottom of the hydrostatic pump.
Than test the pressure as usual.
The relief valve is set to limit the drive pressure to 5200 PSI.
PositionCircuitMake
1OFFNONE
2ONB + I + AX + Y
3STARTB + I + s
Page 59
TORO GM 345 / 325-D Electrical Systems
57
Electrical System
(GM 345 / 325-D)
The electrical system on the 300 Series Goundsmaster can be broken into the following circuits:
1. Starting/Charging.
2. Safety Interlock.
3. Gauges and warning.
4. Engine.
With a basic understanding of these circuits we can troubleshoot a variety of electrical problems.
System Operation
Start Circuit. (GM 345 Shown, 325-D similar)
1. Power from the battery flows to the (-) terminal of the ammeter.
2. The power flows from the (+) terminal of the ammeter to the ignition switch, terminal (X).
3. The power splits and flows to the seat switch.
4. The power splits again and flows to the neutral switch and PTO switch.
5. When both switches are closed the power can flow to the (B) terminal of the ignition switch.
6. When the switch is turned to the start position power flows from the (B) terminal to the (S) terminal.
7. The power then flows to the starter relay and the relay sends power to the starter which cranks the engine.
8. Power is also directed out of the (I) terminal the temperature relay. From the temperature relay the power is
directed to the D.I.S. ignition module and the carb relay.
PositionCircuitMake
1OFFNONE
2ONB + I + AX + Y
3STARTB + I + s
Page 63
TORO GM 345 / 325-D Electrical Systems
61
PTO Engaged, Operator Not In The Seat.
1. If the operator leaves the seat while the PTO is engaged.
2. Power is interrupted by the seat switch.
3. Current stops flowing to the “A” terminal of the ignition switch.
4. Power is stopped to the ignition module and the engine stops.
Caution: Do not disconnect the safety switches because they are there for the operators protection.
Check the operation of the switches daily to be sure the interlock system is operation correctly. If a
switch is malfunctioning, replace it before operating the machine. Replace the switches every 2 years to
be sure of maximum safety.
1. Raise off the seat and engage the PTO switch while the engine is running.
2. The engine should stop within 2 seconds.
If the engine stops, the switch is operating correctly.
If the engine does not stop, there is a problem in the seat switch of the PTO switch.
.
1. Raise of the seat and depress the traction pedal with the PTO disengaged.
2. The engine should stop within 2 seconds.
If the engine stops, the switch is operating correctly. If the engine fails to stop, there is a problem in the seat
The GM325 electrical system has a 40 amp circuit breaker to protect the electrical system from overload.
If all electric functions are lost, resetting the circuit breaker might remedy the problem.
If the circuit breaker open frequently the source of the problem must be found and repaired.
1. The power take-off (PTO) system transmits power from the engine to the cutting deck or other implement
attached to the front of the machine.
2. The PTO lever has two positions: ON (engage) and OFF (disengage). To engage the PTO shaft, slowly
push the PTO lever fully forward to the ON position; this will start the implement or cutting unit blades.
Slowly pull the lever backward to the OFF position to stop the implement’s operation. The only time the PTO
lever should be in the ON position is when the implement or cutting unit is down in the operating position
and the operator is in the seat.
If noisy operation of the cutting unit is encountered and the blade spindles need to be repaired, refer to the
complete repair procedures in the service manual.
The replacement bearing set consists of:
1. The upper and lower bearings races.
2. A snap ring spacer that positions the bearing races in the spindle housing.
3. An outside spacer to set the distance between the bearing races.
4. Two bearings.
5. An inside bearing spacer and an inside spacer ring.
• The inside spacer and the spacer ring position the bearings and set the running clearance.
(NOTE: there in no groove in the shaft that the small ring sets in).
If the spindle does not rotate after assembly, verify that all the spacers and rings are properly installed.
The bearings, races, spacers and snap rings are a matched set and should not be intermixed.
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IMPORTANT: If a new spindle housing is being used, new bearings and the matched snap ring set must
be installed. Never use the old bearings, spacer, and snap ring with a new spindle housing. By contrast,
use only new bearings with cups and spacer when installing bearings into a used spindle housing that
still has a snap ring installed.
Seal replacement
When replacing the spindle seals be careful to install the seals with the seal lips facing in the correct direction.
72” Recycler Deck
1. The upper seal lip faces inward toward the upper bearing.
2. The lower seal lip faces outward, away from the lower bearing.
72” Rear Discharge & Side Discharge
1. The upper seal lip faces outward away from the upper bearing.
2. The lower seal lip faces outward, away from the lower bearing.
Rotary mowers cut grass by the blade’s cutting surface impacting against the grass stems at a high velocity. To
assure good quality of cut, the cutting edge of the blade must be kept in a sharp condition. A dull blade will
produce a ragged cut and will require an excessive amount of engine horsepower to rotate the blade through the
grass. The most common cause for rotary mowers not giving a good quality of cut is due to dull cutting edges
and/or bent blades.
Whenever a blade is removed for sharpening:
A. The blade must be checked to assure that it is not bent and that it has the correct attitude in relation to
the housing and ground surface.
B. The blade must be sharpened correctly.
C. The blade balance must be checked each time the blade is sharpened.
D. When installing the blade, it is very important that the blade retaining bolt or nut be tightened to the
correct torque so it will not loosen during operation.
When a mismatch condition occurs the blade tip height should be checked.
It the blade tip height is different, the blades will cut at a different height and the grass will be uneven.
Another quality of cut problem is striping.
Striping can be caused by the mower blades being sharpened too much that the actual blade length is shorter.
This causes a small line of uncut grass to be left between the blades
Inconsistent height of cut.
An inconsistent height of cut can be caused by the cutting deck not staying at the proper height.
The 300 series Groundsmaster has a float position on the cutting unit raise/lower lever. The lever must be in
float while the unit is mowing. If the lever is not in the float position, the cutting unit may not follow the contour of
the ground.
1. Blade balancing tool
OTC PN. TOR4029 or equivalent
2. Blade holding fixture
OTC PN. TOR4030 or equivalent
3. Portable bench grinder
OTC PN TOR4031 or equivalent
1. Fill the spindle bearing housing with grease
when replacing the bearings. (This assures that
the upper bearing gets grease when the spindle
is greased).
2. The small inside spacer ring does not have a
groove in the spindle to sit in. Install the ring on
the spindle between the bearings.
3. Mower blade bolt torque is 85 to 100 ft/lbs
4. Bent or twisted blades should be replaced. Do
not straighten.
Page 83
TORO GM 345/325-D Cutting Units
Review Questions
81
1. Bearings and spacers should be replaced as a
set
a. True
b. False
2. The drive belt engagement spring should be
adjusted to a length of:
a. 2 1/4 inches
b. 3 3/16 inches
c. 1 1/2 inches
d. 4 inches
3. The cutting unit raise/lower lever should be in
the neutral position when mowing
a. True
b. False
4. Balancing the blade after sharpening is not
necessary.