C7.1 Engines For Caterpillar Built Machines Caterpillar

Use this procedure to troubleshoot the relay for the Electric Fuel Lift Pump (EFLP). Use this procedure if there is a suspected electrical fault with the EFLP.

This procedure covers the following diagnostic codes:

The following background information is related to this procedure:

The EFLP is used in order to provide positive fuel pressure to the high-pressure fuel pump. When the keyswitch is turned to the ON position, the ECM will activate the relay for the EFLP. If the engine is not running, the ECM will deactivate the relay for the EFLP after 2 minutes.

Illustration 1	g02476598
Schematic for the Electric Fuel Lift Pump (EFLP)

Illustration 2	g02454536
View of the pin location on the P1 connector for the EFLP (36) Relay for the EFLP

Test Step 1. Inspect Electrical Connectors and Wiring

1. Check that the fuses are not blown.

2. Check the harness for abrasion and pinch points from the Electric Fuel Lift Pump (EFLP) back to the ECM. Check the harness for abrasion and pinch points from the EFLP back to the battery.

3. Inspect the terminals on the EFLP relay and then inspect the harness connector for the relay. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

4. Inspect the connector for the EFLP. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

5. Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the EFLP.

6. Check the screw for the ECM connector for the correct torque of 6 N·m (53 lb in).

Results:

• All connectors, pins, and sockets are correctly coupled and/or inserted. The harness is free of corrosion, abrasion, and pinch points. The fuses are not blown - Proceed to Test Step 2.

• There is a fault with the harness and connectors -

  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 blown fuses.

  1. Turn the keyswitch to the ON position. Do not start the engine. Check for active diagnostic codes.

  2. Wait for at least 2 minutes for the EFLP to deactivate. Check for active diagnostic codes.

  3. Confirm that the fault has been eliminated.

     Note: If a fuse is replaced and the fault reoccurs, continue with this procedure.

  STOP

Test Step 2. Check for Active Diagnostic Codes

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

2. Turn the keyswitch to the ON position.

   Note: Do not start the engine.

3. Make a note of any active diagnostic codes.

4. Wait for at least 2 minutes for the Electric Fuel Lift Pump (EFLP) to deactivate.

5. Make a note of any active diagnostic codes.

Results:

• Diagnostic code 3666-5 is active when the EFLP is switched off. - Proceed to Test step 3.

• Diagnostic code 3666-6 is active when the EFLP is switched on. - Proceed to Test Step 5.

• An active diagnostic code or a recently logged diagnostic code was not displayed. - There may be a fault with the switched power circuit for the EFLP. The ECM does not monitor the status of this condition. Proceed to Test Step 9.

Test Step 3. Create a Short Circuit at the Fuel Lift Pump Relay

1. Turn the keyswitch to the OFF position.

2. Disconnect the connector for the Electric Fuel Lift Pump (EFLP) relay.

3. Fabricate a jumper wire that is 150 mm (6 inch) long.

4. Use the jumper wire to connect Test Point 1 to Test point 2 on the harness connector for the EFLP relay. Refer to Illustration 1.

5. Turn the keyswitch to the ON position. Do not start the engine.

6. Use the electronic service tool to check for an active 3666-6 diagnostic code.

7. Wait for at least 2 minutes for the EFLP to deactivate. Check for an active 3666-5 diagnostic code.

8. Turn the keyswitch to the OFF position.

9. Remove the jumper. Leave the connector for the EFLP relay disconnected.

Results:

• A 3666-6 diagnostic code was active with the jumper installed. - There are no faults in the wiring for the EFLP relay.

  Repair: Perform the following repair:

  1. Install a replacement relay.

  2. Reconnect the connector for the EFLP relay.

  3. Turn the keyswitch to the ON position. Do not start the engine. Check for active diagnostic codes.

  4. Wait for at least 2 minutes for the EFLP to deactivate. Check for active diagnostic codes.

  5. Confirm that the fault has been eliminated.

  STOP

• A 3666-5 diagnostic code is still active with the jumper installed - Proceed to Test Step 4.

Test Step 4. Measure the Voltage at the Relay Connector

1. Turn the keyswitch to the ON position. Do not start the engine.

2. Measure the voltage between Test Point 1 on the harness connector for the Electric Fuel Lift Pump (EFLP) relay and a suitable ground. Refer to Illustration 1.

Expected Result:

The measured voltage should be a constant 22.0 to 27.0 VDC.

Results:

• OK - The voltage is within the expected range. The wiring to the input of the EFLP relay is OK. Proceed to Test Step 6.

• Not OK - The voltage is not within the expected range. The fault is in the wiring to the input of the EFLP relay.

  Repair: Perform the following repair:

  1. Repair the faulty wiring or replace the faulty wiring.

  2. Turn the keyswitch to the ON position. Do not start the engine. Check for active diagnostic codes.

  3. Wait for at least 2 minutes for the EFLP to deactivate. Check for active diagnostic codes.

  4. Confirm that the fault has been eliminated.

  STOP

Test Step 5. Create an Open Circuit at the Relay

1. Turn the keyswitch to the OFF position.

2. Disconnect the connector for the Electric Fuel Lift Pump (EFLP) relay.

3. Turn the keyswitch to the ON position. Do not start the engine.

4. Use the electronic service tool to check for an active 3666-6 diagnostic code.

5. Wait for at least 2 minutes for the EFLP to deactivate. Check for an active 3666-5 diagnostic code.

Results:

• A 3666-6 diagnostic code is still active with the EFLP relay disconnected. - The EFLP relay is OK. Proceed to Test Step 6.

• A 3666-5 diagnostic code became active with the EFLP relay disconnected. - The wiring for the EFLP relay is OK.

  Repair: Perform the following repair:

  1. Install a replacement relay.

  2. Turn the keyswitch to the ON position. Do not start the engine. Check for active diagnostic codes.

  3. Wait for at least 2 minutes for the EFLP to deactivate. Check for active diagnostic codes.

  4. Confirm that the fault has been eliminated.

  STOP

Test Step 6. Check the Wiring Between the Relay and the ECM for an Open Circuit

1. Turn the keyswitch to the OFF position.

2. Disconnect the P1 connector.

3. Inspect the P1/J1 connector. Refer to Troubleshooting, "Electrical Connectors - Inspect".

4. Disconnect the connector for the Electric Fuel Lift Pump (EFLP) relay.

5. Measure the resistance between P1:36 and Test Point 2 on the harness connector for the EFLP relay.

6. Reconnect the P1 connector. Reconnect the connector for the EFLP relay.

Expected Result:

The resistance should be less than 10,000 Ohms.

Results:

• OK - The resistance is less than 10,000 Ohms. There may be a fault with the ECM. Proceed to Test Step 8.

• Not OK - The resistance is more than 10,000 Ohms. The fault is in the wiring between the ECM and the EFLP relay.

  Repair: Perform the following repair:

  1. Repair the faulty wiring or replace the faulty wiring.

  2. Turn the keyswitch to the ON position. Do not start the engine. Check for active diagnostic codes.

  3. Wait for at least 2 minutes for the EFLP to deactivate. Check for active diagnostic codes.

  4. Confirm that the fault has been eliminated.

  STOP

Test Step 7. Check the Wiring between the Relay and the ECM for a Short Circuit

1. Turn the keyswitch to the OFF position.

2. Disconnect the P1 connector.

3. Inspect the P1/J1 connector. Refer to Troubleshooting, "Electrical Connectors - Inspect".

4. Disconnect the connector for the Electric Fuel Lift Pump (EFLP) relay.

5. Measure the resistance between P1:36 and all the other pins on the P1 connector.

Expected Result:

The resistance between P1:36 and all the other pins on the P1 connector should be more than 10,000 Ohms.

Results:

• OK - The resistance measurements are all more than 10,000 Ohms. The wiring between the EFLP relay and the ECM is not shorted to any other wire. There may be a fault with the ECM. Proceed to Test Step 8.

• Not OK - One or more of the resistance measurements was less than 10,000 Ohms. The short is in the wiring between the EFLP relay and the ECM.

  Repair: Perform the following repair:

  1. Repair the faulty wiring or replace the faulty wiring.

  2. Turn the keyswitch to the ON position. Do not start the engine. Check for active diagnostic codes.

  3. Wait for at least 2 minutes for the EFLP to deactivate. Check for active diagnostic codes.

  4. Confirm that the fault has been eliminated.

  STOP

Test Step 8. 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 test ECM, install a test ECM. Refer to Troubleshooting, "Replacing the ECM".

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

5. Turn the keyswitch to the ON position. Do not start the engine. Check for active diagnostic codes.

6. Wait for at least 2 minutes for the Electric Fuel Lift Pump (EFLP) to deactivate. Check for active diagnostic codes.

Results:

• There are no active 3666 diagnostic codes - 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: Contact the Technical Communicator at a Caterpillar dealer.

  STOP

Test Step 9. Check the Fuse

1. Turn the keyswitch to the ON position. Wait for 5 seconds.

2. Turn the keyswitch to the OFF position. Check the fuse for the Electric Fuel Lift Pump (EFLP). Refer to Illustration 1.

Results:

• The fuse is blown. - There is a short in the circuit for the EFLP. Do not replace the fuse at this stage. Proceed to Test Step 10.

• The fuse is not blown. - There may be an open circuit in the circuit for the EFLP. Proceed to Test Step 13.

Test Step 10. Disconnect the Relay Connector

1. Disconnect the connector for the Electric Fuel Lift Pump (EFLP) relay.

2. Replace the fuse for the EFLP. Wait for 5 seconds.

3. Check the fuse.

Results:

• The fuse is blown. - The fault is in the wiring between Test Point A on the relay and battery+.

  Repair: Repair the faulty wiring or replace the faulty wiring. Replace the fuse. Turn the keyswitch to the ON position to verify that the repair eliminates the fault.

  STOP

• The fuse is not blown. - Proceed to Test Step 11.

Test Step 11. Check the Wiring Between the Relay and the Electric Fuel Lift Pump

1. Disconnect the Electric Fuel Lift Pump (EFLP) relay.

2. Disconnect the EFLP.

3. Check the resistance between Test Point B on the harness connector for the relay and a suitable ground.

Expected Result:

The resistance should be more than 10000 Ohms.

Results:

• OK - The resistance is more than 10000 Ohms. The wiring between the relay and the EFLP is not shorted. Leave the relay and the EFLP disconnected. Proceed to Test Step 12

• Not OK - The resistance is less than 10000 Ohms. The fault is in the wiring between the relay and the EFLP.

  Repair: Repair the faulty wiring or replace the faulty wiring. Turn the keyswitch to the ON position to verify that the repair eliminates the fault.

  STOP

Test Step 12. Check the Relay for a Short Circuit

1. Reconnect the Electric Fuel Lift Pump (EFLP) relay. Leave the connector for the EFLP disconnected.

2. Turn the keyswitch to the ON position. Wait for 5 seconds.

3. Turn the keyswitch to the OFF position. Check the fuse for the EFLP.

Results:

• The fuse is blown. - The short is in the relay.

  Repair: Replace the relay. Replace the fuse.Reconnect the EFLP and the relay. Turn the keyswitch to the ON position to verify that the repair eliminates the fault.

  STOP

• The fuse is not blown - The short is in the EFLP or the lead for the EFLP.

  Repair: Replace the EFLP.Reconnect the EFLP and the relay. Turn the keyswitch to the ON position to verify that the repair eliminates the fault.

  STOP

Test Step 13. Check the Input Voltage to the Relay

1. Disconnect the connector for the Electric Fuel Lift Pump (EFLP) relay.

2. Use a voltmeter to check the voltage between Test Point (A) on the harness connector for the EFLP relay and a suitable ground.

Expected Result:

The measured voltage should be a constant 22.0 to 27.0 VDC.

Results:

• OK - The voltage is within the expected range. The wiring between the battery and the EFLP relay is OK. Proceed to Test Step 14.

• Not OK - The voltage is not within the expected range. The fault is in the wiring between the battery and the EFLP relay.

  Repair: Perform the following repair:

  1. Repair the faulty wiring or replace the faulty wiring.

  2. Turn the keyswitch to the ON position. Do not start the engine. Check for active diagnostic codes.

  3. Wait for at least 2 minutes for the EFLP to deactivate. Check for active diagnostic codes.

  4. Confirm that the fault has been eliminated.

  STOP

Test Step 14. Check the Voltage at the Connector for the Electric Fuel Lift Pump

1. Reconnect the connector for the Electric Fuel Lift Pump (EFLP) relay.

2. Disconnect the connector for the EFLP.

3. Turn the keyswitch to the ON position. Do not start the engine.

4. Measure the voltage at terminal 1 of the harness connector for the EFLP to a suitable ground.

Expected Result:

The measured voltage should be a constant 22.0 to 27.0 VDC.

Results:

• OK - The fuel lift pump is receiving the correct voltage. Proceed to Test Step 15.

• Not OK - The EFLP is not receiving the correct voltage. Proceed to Test Step 16.

Test Step 15. Check the Return Wire for the Electric Fuel Lift Pump

1. Disconnect the connector for the Electric Fuel Lift Pump (EFLP).

2. Turn the keyswitch to the ON position. Do not start the engine.

3. Measure the voltage from terminal 1 to terminal 2 of the harness connector for the EFLP.

Expected Result:

The measured voltage should be a constant 22.0 to 27.0 VDC.

Results:

• OK - The wiring between the EFLP and battery- is OK.

  Repair: Perform the following repair:

  1. Replace the EFLP. Refer to Disassembly and Assembly, "Fuel Priming Pump - Remove and Install".

  2. Turn the keyswitch to the ON position. Do not start the engine.

  3. Confirm that the fault has been eliminated.

  STOP

• Not OK - The fault is in the wiring between the EFLP and battery-.

  Repair: Repair the faulty wiring or replace the faulty wiring.Turn the keyswitch to the ON position to activate the EFLP and confirm that the repair eliminates the fault.

  STOP

Test Step 16. Bypass the Relay

1. Turn the keyswitch to the OFF position.

2. Disconnect the connector for the Electric Fuel Lift Pump (EFLP) relay.

3. Disconnect the connector for the EFLP.

4. Fabricate a jumper wire that is 150 mm (6 inch) long.

5. Use the jumper wire to connect Test Point (A) to Test point (B) on the harness connector for the EFLP relay. Refer to Illustration 1.

6. Measure the voltage from terminal 1 on the harness connector for the EFLP to a suitable ground.

7. Remove the jumper.

Expected Result:

The measured voltage should be a constant 22.0 to 27.0 VDC.

Results:

• OK - The voltage is within the expected range. There is a fault in the relay.

  Repair: Perform the following repair:

  1. Install a replacement relay.

  2. Turn the keyswitch to the ON position to activate the EFLP.

  3. Confirm that the fault has been eliminated.

  STOP

• Not OK - The voltage is not within the expected range. The fault is in the wiring between the EFLP and the EFLP relay.

  Repair: Repair the faulty wiring or replace the faulty wiring.Turn the keyswitch to the ON position to activate the EFLP and confirm that the repair eliminates the fault.

  STOP