* Shorted Fuel Pump Wiring: The most probable cause is a short circuit in the wiring leading to the fuel pump. This could be due to:
* Damaged wires: Wires chafing against the chassis, engine components, or each other can create a short, providing a constant power source to the pump. This is especially likely if the car has seen off-road use or has experienced any impact.
* Corrosion: Corrosion in connectors or wire terminals can also cause a short. Moisture ingress is a common cause of this.
* Internal short in the pump: While less likely, a short within the fuel pump itself could create a path to ground, bypassing the usual switching circuits.
* Faulty Fuel Pump Relay (even though removed): While you've removed the relay, there's a possibility of a faulty relay socket or a short in the wiring *leading* to the relay socket. The relay may be removed, but a short could still bypass it and supply power.
* Power Source Bypassing the Relay: There might be an alternate power source reaching the fuel pump, such as:
* Incorrect wiring: A modification or repair to the wiring harness might have inadvertently created an alternate power path.
* Direct power connection: An unlikely scenario, but a previous owner might have bypassed the relay with a direct power connection to the fuel pump.
* Ignition Switch Issue (extremely rare in this case): A faulty ignition switch, though unlikely given the relay is removed, could still be supplying power in a rare scenario of a completely failed internal switch component.
Troubleshooting Steps:
1. Double-check the relay removal: Absolutely make sure the relay is *completely* disconnected and removed. Try a different relay (although this shouldn't matter if it's truly shorted).
2. Visually inspect the wiring: Carefully examine the wiring harness leading to the fuel pump, looking for damaged, frayed, or corroded wires. Pay close attention near the fuel tank where it is subjected to movement and vibration.
3. Check the relay socket: Inspect the relay socket for any signs of corrosion or damage. Use a multimeter to confirm no power is reaching the socket's power terminals.
4. Disconnect the fuel pump power wire: This is the safest way to stop the pump. Disconnect the wire from the pump itself. Caution: This should be done with the key off and the battery disconnected if possible, to avoid sparks. If the pump stops running after this disconnection, the problem is definitely in the wiring.
5. Multimeter testing: Use a multimeter to trace the wiring, checking for shorts to ground and verifying there's no power getting to the fuel pump when the ignition is off.
If you're not comfortable performing these checks yourself, it's best to take the vehicle to a qualified mechanic. A continuously running fuel pump is a fire hazard, so don't delay addressing this issue.
