* The fuel pump itself is faulty: This is the most common cause. Even with power reaching the relay, a bad pump won't run. You'll need to access the pump (usually involves dropping the fuel tank) to test it directly or replace it.
* Wiring harness issue: A break or short in the wiring between the relay and the pump is possible. Inspect the wiring carefully for damage, especially near the tank and where it might rub against metal.
* Inertia switch: Some vehicles have an inertia switch that cuts power to the fuel pump in the event of a collision to prevent fires. Locate the inertia switch (usually under the dash or in the engine compartment) and check to see if it's tripped. Reset it if necessary.
* Fuel pump relay wiring: While you replaced the relay, the socket or wiring leading *to* the relay might be faulty. Check the socket for corrosion or damaged pins, and test for continuity between the relay socket and the fuel pump.
* Bad ground: A poor ground connection can prevent the fuel pump from receiving the necessary power. Trace the ground wire from the pump and ensure a good connection.
* Computer issue (PCM): Less likely, but the Powertrain Control Module (PCM) could be faulty and not sending the signal to the fuel pump relay. This would require a diagnostic scan tool.
Troubleshooting Steps:
1. Check the inertia switch: This is the easiest and quickest check.
2. Verify power at the fuel pump relay connector: With the ignition on, use a test light or multimeter to check for power at the relay's input and output terminals. This helps isolate whether the problem is before or after the relay.
3. Check the fuel pump wiring for continuity: Disconnect the wiring harness at the pump and use a multimeter to check for continuity between the pump connector and the relay connector.
4. Test the fuel pump directly (if accessible): This is the most definitive way to know if the pump itself is bad. You'll need to apply 12V directly to the pump wires (with appropriate safety precautions) to see if it runs. Accessing the pump usually requires dropping the fuel tank which is more involved.
5. Professional diagnostic: If you can't find the problem, take it to a mechanic. They have diagnostic tools that can pinpoint the issue more effectively.
Remember safety first! Work on a well-ventilated area and disconnect the battery negative terminal before working on the fuel system. Gasoline is highly flammable.
