Generally speaking, fuel pump relays can last anywhere from 50,000 to 100,000 miles, depending on usage of the vehicle, road and environmental conditions, and servicing habits of the car. Located in the electrical system of your car, the relay controls power input to the Fuel Pump, thus allowing it to turn on when required. The wear and tear of internal components-such as contacts and coils-in the relay itself may cause inconsistent power delivery over time. This wear is most prevalent in high-mileage vehicles or those frequently subjected to extreme temperatures, since heat and vibrations hasten the degradation of a relay.
Early symptoms of failure that are normally exhibited by aging relays are intermittent starting issues or occasional stalling because the relay has difficulty in sustaining a consistent flow of current. Industry studies show that relays over seven years old show an increased failure rate of about 30%, which is a good indicator of regular checkups, mostly for those vehicles with more than 100,000 miles. Usually, a fuel pump relay replacement would cost in the area of $15 to $50, depending on the make and model of the vehicle, but it is well worth it compared to avoiding a more serious issue with the fuel system altogether.
High-performance vehicles are designed to burn fuel consistently under heavy acceleration and would, therefore, put extra stress on fuel pump relays, perhaps reducing their life span. It may be that upgrading to a heavy-duty relay, designed to handle increased current loads, extends longevity, as these models are often rated to handle higher power demands.
Power that is inconsistent, coming from a worn relay, also affects the fuel pump and can further cause lean fuel conditions where the engine does not get enough fuel to meet the performance needs. This sets up an imbalance that causes misfires or reduction in fuel efficiency of up to 10%, because the fuel delivery will get sporadic. While even multimeters can be used to test the relays from time to time, this would provide early warnings of weak or failing ones, thus timely replacement will keep fuel pumping efficiently.
Knowing how many miles a Fuel Pump relay lasts and monitoring the warning signs will be one way to assure continued good fuel system performance, minimize the chance of sudden problems, and retain engine efficiency.