C7.1 Engines and Generator Sets Caterpillar

Relay - Test - Fuel Transfer Pump Relay

Usage:

C7.1 770

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:

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Table 1
Diagnostic Codes for the EFLP Relay
J1939 Code	CDL Code	Code Description (code descriptions may vary)	Comments
1075-5	3666-5	Engine Electric Lift Pump for Engine Fuel Supply : Current Below Normal	The Electronic Control Module (ECM) detects the following conditions: There are no active 168 diagnostic codes. The ECM is not attempting to power the relay or there is an open circuit. The ECM has been powered for at least 2 seconds. There is a low current condition in the EFLP relay circuit or wiring for more than 2 seconds. The warning light will come on. The diagnostic code will be logged. The ECM is unable to activate the relay for the EFLP or power the pump. The EFLP will not operate or the EFLP will operate all the time. The engine will not operate.
1075-6	3666-6	Engine Electric Lift Pump for Engine Fuel Supply : Current Above Normal	The ECM detects the following conditions: There are no active 168 diagnostic codes. The ECM is attempting to power the relay or the EFLP. The ECM has been powered for at least 2 seconds. There is a high current condition in the EFLP relay circuit or a short circuit in the wiring for more than 2 seconds. The warning light will come on. The diagnostic code will be logged. The ECM is unable to activate the relay for the EFLP or power the pump. The EFLP will not operate or the EFLP will operate all the time. The engine will not operate. The ECM will continue to attempt to activate the relay or power the pump. If the current is OK for 6 seconds, then the diagnostic code will be cleared.

The following background information is related to this procedure:

The EFLP is used 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 EFLP. If the engine is not running, the ECM will deactivate the EFLP after 2 minutes.

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Illustration 1	g06154498
Schematic for the Electric Fuel Lift Pump (EFLP) with a relay

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Illustration 2	g02138993
View of the pin location on the P1 connector for the EFLP (21) EFLP relay supply

Complete the procedure in the order in which the steps are listed.

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Table 2
Troubleshooting Test Steps	Values	Results
1. Inspect Electrical Connectors and Wiring A. Turn the keyswitch to the OFF position. B. Thoroughly inspect the connectors between the EFLP relay and the engine ECM. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details. C. Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the EFLP relay. D. Check the screw for the ECM connector for the correct torque of 6 N·m (53 lb in). E. Check the harness and wiring for abrasion and for pinch points from the injectors to the ECM.	Loose connection or damaged wire	Result: There is a fault in a connector or the wiring. Repair: Repair any faulty connectors or replace the wiring harness. Ensure that all the seals are properly in place and ensure that the connectors are correctly coupled. Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault. Result: All connectors, pins, and sockets are correctly coupled and/or inserted. The harness is free of corrosion, abrasion, and pinch points. Proceed to Test Step 2.
2. Check for Active Diagnostic Codes A. Connect the electronic service tool to the diagnostic connector. B. Turn the keyswitch to the ON position. Do not start the engine. C. Make a note of any active diagnostic codes. D. Wait for at least 2 minutes for the Electric Fuel Lift Pump (EFLP) to deactivate. Make a note of any active diagnostic codes.	Diagnostic codes	Result: Diagnostic code 1075-5(3666-5) is active when the EFLP is switched off. Proceed to Test Step 3. Result: Diagnostic code 1075-6 (3666-6) is active when the EFLP is switched on. Proceed to Test Step 5. Result: 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 7.
3. Create a Short Circuit at the EFLP Relay A. Turn the keyswitch to the OFF position. B. Disconnect the harness connector for the Electric Fuel Lift Pump (EFLP) relay. C. Fabricate a jumper wire that is 150 mm (6 inch) long. D. 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. E. Turn the keyswitch to the ON position. Do not start the engine. F. Use the electronic service tool to check for an active 1075-6 (3666-6) diagnostic code. G. Wait for at least 2 minutes for the EFLP to deactivate. Check for an active 1075-5 (3666-5) diagnostic code. H. Turn the keyswitch to the OFF position. I. Remove the jumper. Leave the connector for the EFLP disconnected.	Open circuit	Result: A 1075-6 (3666-6) diagnostic code was active with the jumper installed. Repair: Install a replacement EFLP relay. Reconnect the connector for the EFLP relay. Turn the keyswitch to the ON position. Do not start the engine. Check for active diagnostic codes. Wait for at least 2 minutes for the EFLP to deactivate. Check for active diagnostic codes. Confirm that the fault has been eliminated. Result: A 1075-5 (3666-5) diagnostic code is still active with the jumper installed. There is a fault in the wiring or the ECM. Proceed to Test Step 4.
4. Check the Wiring Between the ECM and the EFLP Relay for an Open Circuit A. Turn the keyswitch to the OFF position. B. Disconnect the EFLP relay. Disconnect the J1 connector from the ECM. C. Measure the resistance between the following points: · EFLP relay return terminal on the J1 connector and Test Point 1 on the harness connector for the relay · EFLP relay supply terminal on the J1 connector and Test Point 2 on the harness connector for the relay.	Less than 2.0 Ohms	Result: At least one of the resistance measurements is greater than 2.0 Ohms. Repair: The fault is in the wiring between the EFLP relay and the ECM. Repair the faulty wiring or replace the faulty wiring. Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault. Result: Both resistance measurements are less than 2.0 Ohms. Contact the Dealer Solutions Network (DSN).
5. Create an Open Circuit at the Relay A. Turn the keyswitch to the OFF position. B. Disconnect the harness connector for the EFLP relay. C. Turn the keyswitch to the ON position. Do not start the engine. Wait for at least 2 minutes for the EFLP to deactivate. D. Use the electronic service tool to check for an active 1075-6 (3666-6) diagnostic code. E. Turn the keyswitch to the OFF position.	Short circuit	Result: A 1075-5 (3666-5) diagnostic code is active. There are no faults in the wiring for the EFLP. Repair: Install a replacement relay. Turn the keyswitch to the ON position. Do not start the engine. Wait for at least 2 minutes for the EFLP to deactivate. Check for active diagnostic codes. Confirm that the fault has been eliminated. Result: A 1075-6 (3666-6) diagnostic code is still active. There is a fault in the wiring or the ECM. Proceed to Test Step 6.
6. Check the Wiring Between the Relay and the ECM for a Short Circuit A. Turn the keyswitch to the OFF position. B. Disconnect the P1 connector. C. Inspect the P1/J1 connector. Refer to Troubleshooting, "Electrical Connectors - Inspect". D. Disconnect the connector for the Electric Fuel Lift Pump (EFLP) relay. E. Measure the resistance between P1:21 and all other pins on the P1 connector.	Greater than 1k Ohm	Result: The resistance measurement is less than 1k Ohm. The fault is in the wiring between the EFLP relay and the ECM. Repair: Repair the faulty wiring or replace the faulty harness. Turn the keyswitch to the ON position. Do not start the engine. Check for active diagnostic codes. Wait for at least 2 minutes for the EFLP to deactivate. Check for active diagnostic codes. Confirm that the fault has been eliminated. Result: The resistance measurement is greater than 1k Ohm. Contact the Dealer Solutions Network (DSN).
7. Check the Fuse A. Turn the keyswitch to the ON position. Wait for 5 seconds. B. Turn the keyswitch to the OFF position. Check the fuse for the Electric Fuel Lift Pump (EFLP). Refer to Illustration 1.	Fuse blown	Result: 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 8. Result: The fuse is not blown. There may be an open circuit in the circuit for the EFLP. Proceed to Test Step 8.
8. Check the Power Supply to the Relay Connector A. Disconnect the connector for the EFLP relay. B. Measure the voltage between Test Point A on the harness connector for the relay and a suitable ground. Refer to Illustration 1.	Battery voltage	Result: There is no battery voltage at Test Point A on the harness connector. Repair: Check all wiring between the batteries and the EFLP relay. Make any necessary repairs. Result: Battery voltage is present at Test Point A on the harness connector. Proceed to Test Step 9.
9. Check the Power Supply to the EFLP A. Disconnect the connector for the EFLP. Ensure that the EFLP relay is connected. B. Turn the keyswitch to the ON position. C. Measure the voltage between terminal 1 and terminal 2 on the harness connector for the EFLP.	Battery voltage	Result: There is no battery voltage at the harness connector for the EFLP. Repair: Check all wiring between the EFLP relay and the EFLP. Make any necessary repairs. If the wiring is OK, replace the EFLP relay. Result: Battery voltage is present at the EFLP harness connector. If the EFLP does not activate when the keyswitch is turned to the ON position, replace the EFLP.