* Inert Fuel Pump Relay: This is often the first suspect. The relay acts as a switch, supplying power to the fuel pump. A bad relay will prevent the pump from receiving power, even if the pump itself is good. Testing this is relatively easy with a multimeter or by swapping it with a known good relay (from a similar system if possible, check your owner's manual for relay locations).
* Blown Fuel Pump Fuse: Check the fuse box for a blown fuse associated with the fuel pump. This is a quick and easy check.
* Faulty Fuel Pump: The pump itself could have failed. This is less likely than a relay problem, but still possible after 36+ years. Testing this usually requires access to the pump and a fuel pressure gauge.
* Inertia Switch: Some cars (and potentially your Mark VII, check your owner's manual) have an inertia switch designed to cut power to the fuel pump in a collision to prevent fuel leaks and fire. It's usually a small, resettable switch located under the dash or in the engine compartment. Check if it's tripped and reset it if necessary.
* Low Fuel Level: Sounds obvious, but a very low fuel level can sometimes prevent the pump from priming.
* Wiring Issues: There could be a break or short in the wiring between the relay, fuse, and the fuel pump itself. This would require tracing the wiring for damage or corrosion.
* Computer/PCM Problems: The Powertrain Control Module (PCM or ECM) controls many aspects of the fuel system. While less common as an initial cause, a faulty PCM could prevent the fuel pump from activating. Diagnosing this typically requires a scan tool.
* Fuel Pump Wiring Connector: Check the connector at the fuel pump itself for corrosion or loose connections. Water can ingress over time.
Troubleshooting Steps:
1. Check the fuses: This is the easiest first step.
2. Check and test the fuel pump relay: This is usually the most common cause.
3. Check the inertia switch (if equipped): Reset it if it's tripped.
4. Check the fuel level: Make sure you have enough fuel.
5. Visually inspect wiring: Look for any obvious damage to the wiring harness leading to the fuel pump.
6. Test fuel pump circuit for voltage: A multimeter can help verify if power is reaching the pump. (Caution: Fuel system is flammable!)
If you're not comfortable working on your car's electrical system, it's best to take it to a qualified mechanic for diagnosis and repair. Working with fuel systems can be dangerous if not done properly.
