Signs of a Bad Fuel Pump:
* No crank/start: The engine won't even attempt to turn over. This is a strong indicator of a completely failed pump.
* Slow crank/start: The engine cranks slowly, then sputters and dies. This suggests the pump isn't supplying enough fuel under pressure.
* Engine hesitation/stuttering: The engine runs roughly, hesitates during acceleration, or stutters, especially under load.
* Loss of power: Noticeable decrease in engine power, especially at higher speeds.
* Engine stalls: The engine suddenly cuts out, especially after driving for a while or when slowing down.
* Surging: The engine RPMs fluctuate unexpectedly.
* Weak fuel pressure: This requires a fuel pressure gauge test, which is the definitive test for a weak pump. You'll need a gauge to measure the pressure at the fuel rail. (Consult your repair manual for specifications).
Signs of a Bad Fuel Pump Relay:
* Intermittent problems: The symptoms described above might come and go unpredictably. This is a classic sign of a relay that's failing intermittently. The relay may be overheating or making poor contact.
* No fuel pump prime: When you turn the ignition key to the "ON" position (without starting the engine), you should hear the fuel pump briefly prime. If you don't hear this whirring sound, the relay might be the culprit. (Note: Some cars don't make this sound, so check your owner's manual or a repair manual).
* Clicking sound: You might hear a clicking sound coming from the relay itself when you try to start the car.
Troubleshooting Steps:
1. Listen for the fuel pump prime: Turn the ignition key to "ON" but don't start the engine. Listen carefully near the fuel tank for the whirring sound of the pump.
2. Check the fuel pump relay: Locate the fuel pump relay (consult your owner's manual or a wiring diagram). Visually inspect it for any signs of damage (burns, corrosion). You can often swap it with another relay of the same amperage (carefully noting which relay is which!) to see if that solves the problem. This is a quick and easy test.
3. Check the fuel pump fuse: A blown fuse can also prevent the pump from working; check the fuse box for a blown fuse related to the fuel system.
4. Fuel Pressure Test: This is the most definitive test. Rent or borrow a fuel pressure gauge and test the fuel pressure at the fuel rail. Compare your reading to the specification in your repair manual. Low pressure points to a bad pump or a clogged fuel filter.
5. Inspect fuel lines and filter: Check the fuel lines for cracks, leaks, or kinks. Replace a clogged fuel filter if necessary.
Important Note: If you're not comfortable working on your car's fuel system, it's best to take it to a qualified mechanic. Working with fuel can be dangerous. Improper handling can lead to fire or explosion.
