Signs that a fuel pump is failing include a sudden sharp decrease in overall gas mileage, high car temperature and frequent related engine stalls, slower acceleration or frequent drops in speed when accelerating or going uphill, and fuel gauge needle inconsistency when the car is in motion. It is also possible to diagnose a failing fuel pump by sound; if you cannot hear a brief whirring noise when the car starts, there is likely a fuel pump issue.
One of the most direct ways to diagnose a fuel pump issue is by examining a fuel pressure gauge attached by hand to the Schrader valve on the fuel rail. The pressure gauge tracks the pounds per square inch pressure reading of the fuel injection system and determines whether or not the engine receives adequate fuel.
An automobile with a fuel gauge issue may also experience sudden surges or increases in speed during normal highway driving. This is often the fault of a malfunctioning fuel pressure regulator that is letting too much fuel into the engine rather than too little. Although this problem is not as serious and should not lead to engine failure or stalling, it can still induce dangerous driving conditions.