A fuel pump that doesn't meet the OE minimum fuel flow or pressure requirements for your car can cause driveability and emissions problems.

A weak fuel pump or one that can't generate enough pressure can upset the calibration of your fuel system. This may cause the engine to run lean or starve for fuel under load, causing symptoms such as hard starting (hot or cold), poor idle quality, hesitation or stumbling when accelerating and a loss of high-speed power.

Low fuel pressure can also be a cause of lean misfire at idle and under load, which causes a dramatic increase in hydrocarbon (HC) emissions. A car experiencing this kind of problem usually won't pass an "enhanced" emissions test that measures exhaust emissions under simulated driving conditions on a dynamometer.

Low fuel pressure and/or lean misfire can also trigger the engine warning lamp on 1996 and newer cars equipped with OBD II (on-board diagnostics).

So, if the original fuel pump is weak or has failed, it's important to make sure your replacement fuel pump meets all OE fuel performance specifications.