How would you diagnose a failing fuel pump, and what symptoms would you expect to observe?

• A. No-start or intermittent starting; check fuel pressure with gauge; listen for pump; inspect harness and relay; verify electrical supply; replace if necessary
• B. It makes the engine louder
• C. It increases horsepower
• D. No-start or intermittent starting (typo)

Answer: (A)

Diagnosing a failing fuel pump centers on confirming that the engine is actually receiving the proper fuel delivery and that the pump is being powered correctly. The key symptom to recognize is no-start or intermittent starting, especially when the engine won’t start or runs briefly and then stalls due to insufficient fuel pressure.

Begin by checking fuel pressure with a gauge to see if the pressure is within the engine’s specification. If the pressure is low or zero, that points to a fuel delivery problem. Next, listen for the fuel pump to prime when you turn the ignition to ON; if you don’t hear the pump, it could be the pump itself, the wiring, or the fuse/relay. Inspect the electrical harness and relay to look for damaged wires, corrosion, or a faulty relay that would prevent power from reaching the pump. Finally, verify that the pump is getting a proper electrical supply and ground, ruling out issues in the circuit or control signals from the BCM/ECU.

If the fuel pressure test shows the pump can’t deliver fuel even with correct electrical power, replacement is usually necessary. Other options describe symptoms or effects that don’t align with how fuel delivery problems present, such as an engine becoming louder or gaining horsepower, which aren’t typical indicators of a failing pump.