Fuel Pump Electrical Circuit Diagnosis

FUEL PUMP ELECTRICAL CIRCUIT DIAGNOSIS

Diagnostic Chart (Part 1 Of 2):

Diagnostic Chart (Part 2 Of 2):

For engine controls wiring diagrams, Electrical Diagrams

CIRCUIT DESCRIPTION
When the ignition switch is turned ON, the Vehicle Control Module (VCM) energizes the fuel pump relay which powers the the in-tank fuel pump ON. The in-tank fuel pump remains ON as long as the engine is cranking or running and the VCM is receiving the distributor reference pulses. If there are no reference pulses, the VCM shuts the fuel pump OFF within 2 seconds after the ignition was turned ON or if the engine stops. The VCM will also turn ON the fuel pump when the ignition is turned to the OFF position.

DIAGNOSTIC AIDS
If the fuel pump relay circuit checks out OK, refer to Fuel System Diagnosis. Component Tests and General Diagnostics

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table.

2. Command both the ON and OFF states. Repeat the commands as necessary.

3. This step determines if the condition is located on the coil side or the switch side of the circuit.

4. This step verifies that the VCM is providing voltage to the fuel pump relay.

5. This step tests for an open in the ground circuit to the fuel pump relay.

6. This step determines if a voltage is constantly being applied to the fuel pump relay.

12. To gain access to the fuel pump connector, the fuel tank may need to be removed. Refer to Fuel Sender Assembly Replacement

13. This step determines if the condition with the circuit is intermittent. If the fuse does not open, inspect the supply voltage circuit between the fuse and the fuel pump for an intermittent condition.

15. Use the same amperage fuse in the jumper as is used to protect the fuel pump circuit.

16. To gain access to the fuel pump connector, the fuel tank may need to be removed. Refer to Fuel Sender Assembly Replacement

17. Inspect the splice pack which contains the fuel pump ground and other ground circuits. Be certain all connections within the splice pack are clean and tight.