* Relay is bad: Even with power to the relay, the relay itself might be faulty and not switching the power to the fuel pump. Try swapping the fuel pump relay with another relay of the same amperage rating (check your owner's manual or the relay itself for the rating). If the problem changes, the relay is likely the culprit.
* Wiring issues: A break in the wiring between the relay and the fuel pump, or between the fuse and the injectors, will prevent power from reaching the components. Visually inspect the wiring harness for any damage, corrosion, or loose connections. Pay close attention to the areas where the wires are routed near hot components or areas prone to rubbing.
* Fuel pump is bad: The pump itself might have failed. Power reaching the relay doesn't guarantee the pump is working. You might need to check the fuel pressure with a gauge.
* Injector circuit issue (injectors): Similar to the fuel pump, even with power to the fuse, the injectors themselves could be faulty or have a problem in their control circuit (PCM signal). This often requires more specialized diagnostics.
* Computer (PCM) problem: The Powertrain Control Module (PCM) controls the fuel pump and injectors. A fault in the PCM could prevent it from sending the signal to activate them, even if power is reaching the relay and fuse. This would need a professional diagnostic scan.
* Inertia switch: Some vehicles have an inertia switch that cuts power to the fuel pump in the event of a collision. Make sure this switch hasn't been tripped (usually located under the dash).
Troubleshooting Steps:
1. Check the fuel pump relay: Swap it with another relay.
2. Check the fuel pressure: If you have a fuel pressure gauge, this will directly tell you if the pump is working.
3. Visually inspect wiring: Look for broken, frayed, or corroded wires to the fuel pump, injectors, and relay.
4. Check the inertia switch: Make sure it's not tripped.
5. Use a test light or multimeter: Test the voltage at the fuel pump and injectors themselves to see if they're actually receiving power *when the engine is cranked*. Remember safety precautions when working with electricity.
6. Professional diagnosis: If the above steps don't identify the problem, a professional mechanic with a scan tool can diagnose PCM faults or other more complex electrical issues.
Simply having power at the fuse and relay is only the first step in troubleshooting a no-start or fuel delivery problem. You need to trace the power further down the line.
