* Inertia Switch: This safety device is designed to shut off the fuel pump in a collision. If it's malfunctioning, it might be stuck closed, keeping power to the pump. Check the inertia switch (usually located under the dash or in the engine compartment) – try resetting it by pushing the button.
* Relay Failure: The fuel pump relay acts as a switch, controlled by the ignition system. A faulty relay might be stuck closed, constantly energizing the pump. Replacing the relay is a relatively inexpensive fix.
* Wiring Problems: A short circuit or damaged wiring in the fuel pump circuit could be bypassing the normal shutoff. This could involve a damaged wire, a corroded connection, or a short to ground. This requires careful checking of all wiring related to the fuel pump.
* PCM (Powertrain Control Module) Issue: While less common, a problem with the PCM (the computer controlling the engine) could be sending a continuous signal to the fuel pump, even with the key off. This would require diagnostic tools to verify.
* Fuel Pump Control Module (if equipped): Some vehicles have a dedicated module to control the fuel pump. A faulty module could be the culprit.
* Aftermarket additions: Any aftermarket accessories or modifications to the electrical system could be interfering and causing this.
Troubleshooting Steps:
1. Check the inertia switch: This is the easiest and cheapest first step.
2. Listen carefully: Try turning the key on and off. Does the pump run for a normal short period to prime, then shut off? If it runs continuously even immediately after turning the ignition off, the problem is likely not just a priming issue.
3. Check the fuel pump relay: Locate the relay and try swapping it with a known good one from another circuit (if possible and safe).
4. Visual inspection: Inspect the wiring harness connected to the fuel pump and relay for any damage, corrosion, or loose connections.
Important Safety Note: Working on fuel system components can be dangerous. Always disconnect the negative battery terminal before working on the fuel system. Fuel is flammable, and you risk injury or fire if you are not careful. If you're not comfortable working on your car's electrical system, it's best to take it to a qualified mechanic.
