C1.5 and C2.2 Industrial Engines Caterpillar

Use this procedure if there is a suspected problem with the electric fuel lift pump circuit.

Illustration 1	g03341717
Schematic diagram of the fuel lift pump relay circuit

Illustration 2	g03342141
View of the pin location on the P1 connector for the fuel lift pump relay (53) Fuel lift pump relay

Test Step 1. Inspect Electrical Connectors and Wiring

1. Turn the keyswitch to the OFF position.

2. Check the fuses.

3. Check the harness for abrasion and pinch points from the relay back to the ECM and from the relay back to the battery.

4. Check the harness for abrasions and pinch points from the fuel lift pump back to the relay.

5. Thoroughly inspect the relay and the connector for the relay.

6. Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the fuel lift pump relay.

Results:

• All connectors, pins, and sockets are correctly coupled and/or inserted. The harness and connectors are free of corrosion, abrasion, and pinch points. The fuses are OK. - Proceed to Test Step 2.

• There is a fault with the harness and connectors -

  Repair: Perform the following repair:

  Repair the connectors or the harness and/or replace the connectors or the harness. Ensure that all of the seals are correctly in place and ensure that the connectors are correctly connected. Replace any blown fuses.

  STOP

Test Step 2. Override the Fuel Lift Pump Relay

1. Turn the keyswitch to the OFF position.

2. Connect the electronic service tool to the diagnostic connector.

3. Turn the keyswitch to the ON position.

4. Use the electronic service tool to activate the "Engine Fuel Supply Lift Pump Relay Override".

   Note: The "Engine Fuel Supply Lift Pump Relay Override" activates the fuel lift pump relay for 10 seconds.

5. Turn the keyswitch to the OFF position.

Results:

• The fuel lift pump operates when the "Engine Fuel Supply Lift Pump Relay Override" is activated. - The fuel lift pump relay circuit is operating correctly at this time.

  Repair: If there is an intermittent fault, refer to Troubleshooting, "Electrical Connectors - Inspect" in order to identify the fault.

  STOP

• The fuel lift pump does not operate when the "Engine Fuel Supply Lift Pump Relay Override" is activated. - Proceed to Test Step 3.

Test Step 3. Check the Voltage at the Fuel Lift Pump Relay

1. Turn the keyswitch to the OFF position.

2. Disconnect the fuel lift pump relay.

3. Turn the keyswitch to the ON position.

4. Use a suitable multimeter to measure the voltage between the following points:

   • Test Point A on the harness connector for the relay and a suitable ground

   • Test Point D on the harness connector for the relay and a suitable ground

5. Turn the keyswitch to the OFF position.

Expected Result:

The measured voltage should be between 11 VDC and 14 VDC.

Results:

• The measured voltage is within the expected range - Proceed to Test Step 4.

• The voltage is not within the expected range - The fault is in the battery supply wiring to the fuel lift pump relay.

  Repair: Replace the faulty wiring. Reconnect the fuel lift pump relay.

  Use the electronic service to clear all logged diagnostic codes and verify that the repair eliminates the fault.

  STOP

Test Step 4. Check the Wiring Between the Relay and the ECM

1. Turn the keyswitch to the OFF position.

2. Disconnect the fuel lift pump relay. Disconnect the P1 connector from the ECM.

3. Use a suitable multimeter to measure the resistance between Test Point B on the harness connector for the relay and P1:53.

Results:

• The measured resistance is greater than 2 Ohms - The fault is in the wiring between the relay and the ECM

  Repair: Replace the faulty wiring.

  Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault.

  STOP

• The measured resistance is less than 2 Ohms - Reconnect the P1 connector. Leave the relay disconnected. Proceed to Test Step 5.

Test Step 5. Check the Resistance of the Relay Coil

1. Use a suitable multimeter to measure the resistance between Test Point A and Test Point B on the fuel lift pump relay.

Results:

• The multimeter indicates an open circuit - The fault is in the fuel lift pump relay.

  Repair: Install a replacement relay.

  Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault.

  STOP

• The multimeter indicates continuity across the relay coil - Reconnect the fuel lift pump relay. Proceed to Test Step 6.

Test Step 6. Check the Voltage at the 6-Pin Connector

1. Turn the keyswitch to the OFF position.

2. Disconnect the 6-pin connector.

3. Turn the keyswitch to the ON position.

4. Use the electronic service tool to activate the "Engine Fuel Supply Lift Pump Relay Override".

   Note: The "Engine Fuel Supply Lift Pump Relay Override" activates the fuel lift pump relay for 10 seconds.

5. Use a suitable multimeter to measure the voltage at pin 2 on the relay side of the 6-pin connector while the "Engine Fuel Supply Lift Pump Relay Override" is active.

6. Turn the keyswitch to the OFF position.

Expected Result:

The measured voltage is between 11 VDC and 14 VDC.

Results:

• The measured voltage is not within the expected range - Leave the 6-pin connector disconnected. Proceed to Test Step 7.

• The measured voltage is within the expected range - Reconnect the 6-pin connector. Proceed to Test Step 8.

Test Step 7. Check the Wiring Between the Relay and the 6-Pin Connector

1. Turn the keyswitch to the OFF position.

2. Disconnect the fuel lift pump relay.

3. Use a suitable multimeter to measure the resistance between Test Point C on the harness connector for the relay and terminal 2 on the fuel lift pump side of the 6-pin connector.

Results:

• The measured resistance is greater than 2 Ohms - The fault is in the wiring between the relay connector and the 6-pin connector.

  Repair: Replace the faulty wiring.

  Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault.

  STOP

• The measured resistance is less than 2 Ohms -

  Repair: Install a replacement fuel lift pump relay.

  Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault.

  If the fault is still present with the replacement relay, proceed to Test Step 10.

Test Step 8. Check the Voltage at the Fuel Lift Pump Connector

1. Turn the keyswitch to the OFF position.

2. Disconnect the connector for the fuel lift pump.

3. Turn the keyswitch to the ON position.

4. Use the electronic service tool to activate the "Engine Fuel Supply Lift Pump Relay Override".

   Note: The "Engine Fuel Supply Lift Pump Relay Override" activates the fuel lift pump relay for 10 seconds.

5. Use a suitable multimeter to measure the voltage between pin 1 on the harness connector for the fuel lift pump and a suitable ground while the "Engine Fuel Supply Lift Pump Relay Override" is active.

6. Turn the keyswitch to the OFF position.

Expected Result:

The measured voltage should be between 11 VDC and 14 VDC.

Results:

• The measured voltage is not within the expected range - The fault is in the wiring between the 6-pin connector and the fuel lift pump connector.

  Repair: Replace the faulty wiring.

  Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault.

  STOP

• The measured voltage is within the expected range - Leave the fuel lift pump connector disconnected. Proceed to Test Step 9.

Test Step 9. Check that the Fuel Lift Pump is Grounded

1. Turn the keyswitch to the ON position.

2. Use the electronic service tool to activate the "Engine Fuel Supply Lift Pump Relay Override".

   Note: The "Engine Fuel Supply Lift Pump Relay Override" activates the fuel lift pump relay for 10 seconds.

3. Use a suitable multimeter to measure the voltage between terminal 1 and terminal 2 on the harness connector for the fuel lift pump while the "Engine Fuel Supply Lift Pump Relay Override" is active.

4. Turn the keyswitch to the OFF position.

Expected Result:

The measured voltage should be between 11 VDC and 14 VDC.

Results:

• The measured voltage is within the expected range -

  Repair: Perform the following repair:

  1. Reconnect all connectors.

  2. Use the electronic service tool to activate the "Engine Fuel Supply Lift Pump Relay Override".

     Note: The "Engine Fuel Supply Lift Pump Relay Override" activates the fuel lift pump relay for 10 seconds.

  3. If the fuel lift pump does not operate, install a replacement fuel lift pump.

  4. Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault.

  STOP

• The measured voltage is not within the expected range. - The fault is in the ground wire between terminal 2 on the fuel lift pump connector and engine ground.

  Repair: Replace the faulty wiring.

  Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault.

  STOP

Test Step 10. Check the ECM

1. Make sure that the latest flash file for the application is installed in the ECM. Refer to Troubleshooting, "Flash Programming".

2. Contact the Technical Communicator at a Cat dealer.

   Note: This consultation can greatly reduce the repair time.

3. If the Technical Communicator recommends the use of a replacement ECM, install a replacement ECM. Refer to Troubleshooting, "Replacing the ECM".

4. Use the electronic service tool in order to clear all logged diagnostic codes.

5. Use the electronic service tool to turn on the "Engine Fuel Supply Lift Pump Relay Override" override. Check for active diagnostic codes.

6. Use the electronic service tool to turn off the "Engine Fuel Supply Lift Pump Relay Override" override.

Results:

• The fuel lift pump operates while the "Engine Fuel Supply Lift Pump Relay Override" is active. - The replacement ECM functions correctly.

  Repair: Perform the following procedure:

  1. Reconnect the suspect ECM.

  2. If the fault returns with the suspect ECM, replace the ECM.

  3. Use the electronic service tool in order to clear all logged diagnostic codes and then verify that the repair eliminates the fault.

  STOP

• Not OK - The fault is still present with the replacement ECM. Do not use the replacement ECM.

  Repair: Repeat this test procedure from Test Step 1.

  STOP