A failing fuel pump in a Porsche can cause major engine performance issues and expensive repairs. Symptoms of a weak or failed fuel pump include loss of power when the engine is under stress, reduced fuel mileage as the pump allows too much fuel into the engine, sputtering as the pump struggles to provide fuel consistently, inability to accelerate smoothly due to irregular fuel pressure, and decreased fuel pressure leading to misfiring, rough idling, and stalling. If a Porsche displays any of these issues, it should be brought to an auto repair shop to have the fuel pump inspected and properly diagnosed.