Service manual

9. Troubleshooting 9-2013

6. Verify the temperature sensor resistance. Replace as necessary.

7. Measure the temperature sensor wiring (J1-33) for continuity. Repair or replace as

necessary.

8. Visually inspect the alternator fan for missing or damaged fins. Replace the fan if

necessary.

9.31 Low Fuel Pressure - Fault Code 78

Logic: Controller sensed fuel pressure switch open and approaching fault declaration: 14, 15,

22 or 36.

Possible Causes: Wire connections, fuel system, fuel pressure switch,

Diagnosis & Solution:

1. Verify that the Last Fault is FC 78: Yes, continue diagnosis; No, troubleshoot actual last

fault.

2. Verify the fuel supply and regulator lock off pressures.

3. Measure steady DC voltage at the fuel solenoid while the generator set is running; repair

wiring as necessary.

4. Verify the fuel lines are not kinked or broken/cracked.

5. Run the generator set on shop fuel supply; verify the tank level and fuel line condition.

6. Check the generator set fuel lines for damage: replace the fuel line as required.

7. Check for fuel pressure switch continuity to ground while the generator set is running.

8. Check for fuel pressure switch continuity across its terminals while fuel system pressure is

applied.

9. Check the fuel pressure switch wiring for an open circuit.

10. Disconnect the generator set control J1 connector, verify that the J1 pins are fully inserted

and inspect pin condition using the steps below:

• Use the test points of the tester tool #420-0603

• Use a mating pin connector, a pin gauge of the same size (.045") as the mating

control connector pin, or any suitable device that will not damage the inside contact

wipers of the pin socket

• Insert, repair, or replace pins as necessary.

9.32 Failure To Transfer To Generator Set - Fault Code

NOTICE

Only with 6634 and 6635 (to be performed by a Cummins Technician only)

Only with 6868 and 6869

Logic: Controller commanded transfer switch to standby position but standby position feedback

not received after the 5 second transfer time delay.

106 A030A239 (Issue 10)