* Inertia Switch: This safety device shuts off the fuel pump in a collision. It's usually located under the dash or in the engine compartment. If it's tripped, it needs to be reset (usually a button to push). Check this first.
* Fuel Pump Relay: This relay controls the power to the fuel pump. Heat and vibration can cause relay contacts to fail intermittently. Replacing the relay is relatively inexpensive and often solves this type of problem.
* Cranking Sensor (Crankshaft Position Sensor): If this sensor is failing intermittently, the PCM (Powertrain Control Module) might not signal the fuel pump to activate because it's not detecting the engine's rotation. A faulty signal will prevent the fuel pump from priming.
* Fuel Pump Wiring/Connectors: Corrosion, loose connections, or damaged wiring in the circuit leading to the fuel pump can cause intermittent operation. Inspect the wiring harness, connectors, and grounds related to the fuel pump. Look for any signs of chafing, corrosion, or loose connections. Pay close attention to the connectors at the fuel pump itself.
* Fuel Pump Driver Module (PCM related): In some cases, the problem might lie within the PCM itself, specifically the circuitry that controls the fuel pump. This is less likely than the other issues but possible if other components have been ruled out. A faulty PCM would require more advanced diagnostics or replacement.
* Fuel Pump Itself: While less likely given the intermittent nature of the problem, a failing fuel pump could exhibit these symptoms. The pump might be nearing the end of its life, its internal components are becoming unreliable due to wear.
Troubleshooting Steps:
1. Check the inertia switch: Reset it if it's tripped.
2. Check the fuel pump relay: Visually inspect it for damage, and consider swapping it with another relay of the same amperage (if possible, to see if that solves the issue).
3. Listen for the fuel pump prime: When you turn the ignition key to the "ON" position (without cranking), you should hear a brief whirring sound from the fuel pump area (usually in the rear of the vehicle near the fuel tank). If you don't hear it, this strongly suggests a problem in the relay, wiring, or PCM.
4. Have the fuel system pressure tested: A professional mechanic can measure the fuel pressure to determine if the pump is delivering sufficient pressure.
5. Inspect the wiring: Carefully examine the wiring harness, connectors, and grounds for any signs of damage or corrosion.
6. Advanced diagnostics: If you can't identify the problem using the above steps, you might need to use a scan tool to check for diagnostic trouble codes (DTCs) that could pinpoint the issue more precisely. This will often help narrow down whether the problem is sensor-related or within the PCM.
It's strongly recommended that you have a qualified mechanic diagnose this issue, especially if you're not comfortable working with automotive electrical systems. Attempting repairs without proper knowledge can be dangerous and may lead to further damage. The intermittent nature of the problem makes it tricky to pinpoint without systematic troubleshooting.
