Various symptoms can result from a faulty fuel pump and may lead to an inability of the engine to either stall, accelerate poorly, or not start easily. The main symptom of a bad fuel pump includes inconsistent fuel pressure. Most vehicles usually need 40 to 60 PSI fuel pressure, but it is always best to check for the specific model. If this fuel pressure is always lower than this range, there might be something wrong with the fuel pump. About 40% of all problems in the engine can be related to a malfunctioning fuel pump unable to maintain correct fuel pressure.
Another common symptom of the failure is hesitation or stumbling of the engine. This mostly happens when the fuel pump is not able to maintain proper and continuous fuel flow under load or during acceleration. For instance, it may show hesitation in acceleration like when the accelerator pedal has been pressed, the vehicle simply cannot pick up speed; 25% of this kind of acceleration problem arises due to a faulty fuel pump, according to automotive professionals. If you feel momentary hesitation while driving normally and also during urgent acceleration needs, it may be related to a weak or faulty fuel pump.
Difficulty in starting the engine is another common symptom. A defective fuel pump may struggle to deliver fuel to the engine, especially during cold starts. As a result, the engine may turn over several times before firing. In severe cases, the engine may fail to start altogether. According to the NHTSA, a failure in fuel pumps is listed as one of the three major causes of failure in vehicle start-ups, at an estimated 15% of such cases.
Another red flag is excessive noise from the fuel pump. A healthy fuel pump is normally quiet, but a malfunctioning one can produce odd or loud noises. Most of these noises are because the pump is struggling with its inner mechanisms and could portend an imminent failure of the pump. Many repair professionals advise the replacement of the fuel pump once it has started making abnormal noises to save the engine from further damage.
Finally, your car may stall, especially at high speeds or even at idle, when the fuel pump is failing. Due to its inability to provide a constant flow of fuel, it causes engine stalling, which may not be easily detectable without proper equipment. Vehicle manufacturers have estimated through studies that approximately 20% of all engine stalling is due to the fuel pump not being able to deliver adequate fuel under higher demand conditions.
In all these cases, fuel pressure and listening for unusual noises are some of the diagnostic actions to be performed to verify if your Fuel Pump is defective.