Symptoms suggesting a bad fuel pump:
* No start: The engine cranks but won't fire. This is a strong indicator, especially if it's intermittent.
* Hesitation or sputtering: The engine runs poorly, especially under acceleration, then may die.
* Loss of power: The car feels sluggish and accelerates slowly.
* Surging: The engine speed fluctuates erratically.
* Engine cuts out: The engine suddenly stops running, especially after a period of driving or when the fuel tank is low.
* Whining noise from the fuel tank: This is a less common symptom, but a noticeable whining sound near the fuel tank while the engine is running can suggest a failing pump.
How to troubleshoot:
1. Check the fuel pressure: This is the most definitive test. You'll need a fuel pressure gauge and the appropriate adapter to connect it to the fuel rail. The pressure should be within the specifications outlined in your owner's manual (typically around 30-40 PSI for a '96 Mustang, but consult your manual for precise values). Low or no pressure points strongly to a fuel pump problem.
2. Listen for the fuel pump prime: Turn the ignition key to the "ON" position (don't crank the engine). You should hear a brief whirring sound from the fuel tank area for a second or two. This indicates the pump is activating and priming the fuel lines. No sound suggests a problem with the pump, the relay, or the pump's wiring.
3. Check the fuel pump relay: The fuel pump relay is an electrical component that activates the fuel pump. A bad relay can prevent the pump from working even if the pump itself is fine. You can swap it with a known good relay from another circuit (check your owner's manual for relay locations and diagrams).
4. Inspect the fuel filter: A clogged fuel filter can restrict fuel flow, mimicking a bad pump. Replace the fuel filter (it's relatively inexpensive) if it's dirty or hasn't been changed in a while. This is a good preventative maintenance step regardless.
5. Check the fuel pump fuse: A blown fuse can also prevent the pump from operating. Check the fuse box (usually under the hood or in the cabin) for a blown fuse related to the fuel pump.
Important Considerations:
* Safety: Fuel is flammable. Work in a well-ventilated area and avoid sparks or open flames.
* Professional help: If you're not comfortable performing these checks or repairs yourself, it's best to take your Mustang to a qualified mechanic. Misdiagnosis can lead to unnecessary repairs or even damage to your vehicle.
* Year and engine: The specifics of testing and diagnosing can vary slightly depending on the exact engine in your '96 Mustang (4.6L V8, 3.8L V6, etc.). Consult a repair manual specific to your vehicle for precise specifications and diagrams.
If you've performed these checks and still suspect a faulty fuel pump, replacement is usually the next step. It's a somewhat involved job that often requires dropping the fuel tank. Again, professional help may be the best option if you lack experience with automotive repairs.
