Troubleshooting

(Table 28, contd)
Troubleshooting Test Steps
Values Results
4. Throttle Position Sensor/Throttle Switches (if equipped)
A. Turn the start switch to the ON position.
B. Run the engine until the speed is equal to the maximum no-load
speed.
C. Use the electronic service tool to make sure that the throttle is
set to reach the maximum no-load speed.
Electrical
connections
Result: The throttle response is not as expected.
Repair: If the maximum no-load speed cannot be ob-
tained refer to Troubleshooting, “Switch Circuits - Test
(Throttle Switch)” and Troubleshooting, “Mode Selection -
Test”.
If the engine speed is erratic refer to Troubleshooting,
“Speed Control - Test”.
Result: All responses are normal.
Proceed to Test Step 5.
5. High-Pressure Fuel Pump
Note: The fuel injection pump that is installed by the factory is a
nonserviceable item. If any fault occurs within the fuel injection
pump, the fuel injection pump must be replaced.
A. Use the electronic service tool to select the correct screen in or-
der to display any diagnostic trouble codes that relate to the fuel
injection pump.
HP fuel pump Result: There are diagnostic codes associated with the
high-pressure fuel pump.
Repair: Diagnose the codes. Refer to Troubleshooting,
“Diagnostic Trouble Codes”.
If necessary, replace the high-pressure fuel pump.
Result: The high-pressure fuel pump is OK.
Proceed to Test Step 6.
6. Low Compression (Cylinder Pressure)
A. Perform a compression test. Refer to Systems Operation, Test-
ing, and Adjusting, “Compression - Test ”.
Cylinder
compression
Result: The results of the compression test are outside
the specifications.
Repair: Investigate the cause and rectify any faults.
Note: Possible causes of low compression are shown in
the following list:
· Loose glow plugs
· Faulty piston
· Faulty piston rings
· Worn cylinder bores
· Worn valves
· Faulty cylinder head gasket
· Damaged cylinder head
Result: The results of the compression test are OK.
Proceed to Test Step 7.
(continued)
72 UENR0612-07
Symptom Troubleshooting
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