1. Wiring and Connections:
* Loose or Corroded Connections: Even if plugged in, the connector itself might have loose or corroded pins. Inspect the connector at the fuel pump and the fuel pump relay carefully. Clean any corrosion with a wire brush and electrical contact cleaner.
* Broken Wires: Wires leading to the fuel pump can be damaged by age, rodents, or physical impacts. Trace the wiring harness from the pump to the relay and then to the power source, looking for breaks, chafing, or damage.
* Faulty Inertia Switch: This safety device cuts power to the fuel pump in a collision. If it's tripped, it needs to be reset (usually a button under the dash).
2. Relay Problems:
* Fuel Pump Relay Failure: The relay acts as a switch, turning the pump on and off. A failed relay won't send power to the pump, even with a good connection. Test the relay (swap it with a known good one of the same type) or replace it.
3. Electrical Components:
* Fuel Pump Control Module (if applicable): Some vehicles have a dedicated control module for the fuel pump. A faulty module can prevent power from reaching the pump. This is less likely on a '96 DeVille but possible.
* Blown Fuse: Check the fuse related to the fuel pump in the fuse box(es).
* Bad Fuel Pump Driver Circuit: This is the circuitry that controls the power to the relay. Testing this usually requires a multimeter and understanding of automotive electrical systems.
4. Fuel Pump Issues (Less Likely if No Power at Connector):
* Fuel Pump Failure: While less likely if you have zero power at the connector, a completely failed pump could draw excessive current, blowing a fuse or causing a short that interrupts the power.
Troubleshooting Steps:
1. Check the Fuse: This is the easiest first step.
2. Inspect the Wiring and Connectors: Look for obvious damage, corrosion, or loose connections.
3. Test the Fuel Pump Relay: Swap it with a known good relay.
4. Use a Multimeter: With the ignition on, check for power at the fuel pump connector. You should have battery voltage at one pin and ground at another. If you don't, trace the wiring back.
5. Inertia Switch Check: Locate and reset the inertia switch.
Important Note: Working on fuel system components involves potential fire hazards. Disconnect the battery negative terminal before starting any work. If you're not comfortable with automotive electrical systems, it's best to take your vehicle to a qualified mechanic.
