Fuel Pump Electrical Circuit Diagnosis
CIRCUIT DESCRIPTIONWhen you turn ON the ignition switch the control module enables the fuel pump relay which powers the fuel pump on. The fuel pump remains ON as long as the engine is cranking or running and the control module receives ignition reference pulses. If there are no ignition reference pulses, the control module shuts the fuel pump OFF within 2 seconds after the ignition was switched to the ON position, or if the engine stops.
DIAGNOSTIC AIDS
The following conditions may have caused the fuel pump fuse to open:
^ The fuse is faulty.
^ There is an intermittent short in the fuel pump power feed circuit.
^ The fuel pump has an intermittent internal problem.
For an intermittent condition, refer to Intermittent Conditions. Intermittent Conditions
TEST DESCRIPTION
Steps 1-14:
Steps 15-27:
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 PCM 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.
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.
17. Inspect the ground connection for the fuel pump. Be certain all ground connections are clean and tight.