1. Verify Relay and Fuse Replacement:
* Double-check: Ensure you replaced the *correct* fuse and relay. A blown fuse might indicate a short circuit somewhere else in the system. Carefully examine the new fuse and relay to make sure they're seated properly.
* Test the relay: Even a new relay can be faulty. Use a multimeter to test the relay's continuity in different positions (energized/de-energized). There are many online tutorials showing how to test a relay.
2. Power and Ground Checks:
* Power at the relay: With the ignition ON, use a multimeter to check for power at the power input terminal of the fuel pump relay. If no power is present, trace the wire back towards the source (usually the ignition switch or a fuse in the main fuse box). A wiring diagram is crucial here.
* Ground: The fuel pump relay and the fuel pump itself need a good ground. Locate the ground wire for the relay and the fuel pump, and clean them thoroughly. A poor ground connection can easily prevent the pump from working. Test the continuity to the ground point using your multimeter.
* Power at the pump: Directly test for power at the fuel pump connector with the ignition ON. This will determine if the problem is before or after the relay. Be extremely careful here as you'll be working near fuel. Disconnect the battery negative terminal before doing this.
3. Wiring Inspection:
* Visual inspection: Carefully inspect the wiring harness between the fuel pump relay and the fuel pump for any signs of damage, chafing, or corrosion. Pay close attention to areas where the wiring might rub against the chassis or other components.
* Wiring diagram: Obtain a wiring diagram for your specific 2002 Chevy Cavalier. This will be invaluable in tracing the circuit and identifying all the components involved. You can often find these online through repair manuals or forums. A Haynes or Chilton manual for your car would be a great investment.
* Continuity test: If you suspect a broken wire, use a multimeter to test the continuity of the wires between the relay and the fuel pump.
4. Fuel Pump Inertia Switch:
* Location: Many GM vehicles have an inertia switch that cuts power to the fuel pump in the event of a collision. Locate this switch (usually under the dash or in the engine compartment) and check if it's tripped. There's usually a button to reset it.
5. Fuel Pump itself:
* Difficult to test in-situ: Testing the fuel pump directly requires special tools and expertise unless you're very experienced.
* If all else fails: If all the previous steps don't reveal the issue, the pump itself might be the culprit. This usually requires removing the fuel pump to test it properly. This is potentially messy and requires specialized tools.
Important Safety Precautions:
* Disconnect the negative battery terminal before performing any electrical tests or working on the fuel system.
* Work in a well-ventilated area when dealing with fuel.
* Avoid sparks or open flames near the fuel system.
* Use caution when working under the car. Secure it properly on jack stands.
If you're not comfortable working with car electrical systems, it's best to take your Cavalier to a qualified mechanic. Troubleshooting fuel system issues can be complex, and an incorrect diagnosis could lead to further damage or even injury.
