* Engine cuts out unexpectedly: This is a classic symptom. The engine runs fine, then suddenly dies without warning. It might restart after a short wait, but will likely die again.
* Difficulty starting: The engine cranks, but struggles to start, especially after the vehicle has been sitting for a while. It might require several attempts before firing up.
* Loss of power or hesitation: The engine might sputter, hesitate, or lose power during acceleration, especially under load (e.g., climbing a hill).
* Whining noise from the fuel tank: A failing fuel pump can produce a whining or buzzing sound, especially when the ignition is turned on. You might need to listen carefully, possibly near the fuel tank.
* Weak fuel pressure: This requires a fuel pressure gauge to measure. Low fuel pressure is a definitive sign of a failing fuel pump.
* Engine runs only when the fuel tank is nearly full: This indicates the pump may not be able to pull fuel from the bottom of the tank.
Important Note: While these are common symptoms of a bad fuel pump, they can also indicate other issues like a clogged fuel filter, faulty fuel injectors, problems with the ignition system, or even a PCM (Powertrain Control Module) malfunction. Proper diagnosis requires testing.
Before replacing the fuel pump (which is a major job):
1. Check the fuel filter: This is a much cheaper and easier fix and a clogged filter can mimic a failing pump.
2. Check the fuel pressure: Use a fuel pressure gauge to measure fuel pressure. This will confirm whether the pump is delivering adequate pressure.
3. Inspect the fuel pump relay: A faulty relay can prevent the pump from functioning correctly.
If the fuel pressure is low, after ruling out other easier-to-check issues, a bad fuel pump is highly probable. Remember to consult a repair manual or qualified mechanic for proper diagnosis and repair procedures. Working with fuel systems requires caution; fuel is flammable.
