3512B Marine Auxiliary Engine Caterpillar

• Fuel level

• Low Idle/High Idle switch

• Electrical power supply to the Electronic Control Module (ECM)

• Fuel supply

Perform the following tests in order:

1. Monitor fuel level during engine operation. If a low fuel level causes the problem, maintain a higher fuel level.

2. Use the Caterpillar Electronic Technician (ET) in order to monitor the status of the Low Idle/High Idle switch. Observe the switch position. Move the switch from the Low Idle position to the High Idle position. The Cat ET should indicate the correct position. Refer to the diagnostic functional test Troubleshooting, "Low Idle/High Idle Switch".

3. Check the Cat ET for the following logged Diagnostic Codes: 168-01 and 168-02. Inspect the wires and the power relay. Check the power to the ECM and the ground connections. Refer to Electrical System Schematic. Refer to the diagnostic functional test Troubleshooting, "Electrical Power Supply".

4. Check fuel lines for the following problems: restrictions, collapse and pinched line Repair the lines and/or replace the lines. Refer to the Systems Operation, "Fuel System".

   1. Check the fuel tank for foreign objects which may block the fuel supply. Check for air in the low pressure fuel supply system after you perform the following procedures:
      • Replacing the fuel filters

      • Working on the low pressure fuel supply circuit

      • Replacing fuel injectors

   2. Purge air from the low pressure fuel supply circuit with the hand priming pump and by cranking the engine in 30 second cycles. After you crank the engine, stop for two minutes. This will allow the starting motor to cool. Loosen the vent plug at the fuel return. The plug is located on the rear upper left side of the engine block. Hand prime the engine again if air in fuel continues. A sight glass in the low pressure supply line is helpful in diagnosing air in the fuel.

   3. Check fuel quality. In temperatures below 0 °C (32 °F), check for solidified fuel (wax). Check the fuel pressure while the engine is cranking. Check the fuel pressure at the filter. Refer to Testing and Adjusting, "Fuel Pressure" for correct pressure values. If the pressure is low, check for plugged fuel filters. If the fuel pressure is still low check the following items: fuel transfer pump, fuel transfer pump coupling and fuel pressure regulating valve. Check for a combustion problem.