The fuel pump relay is an electronic component that is found on virtually all vehicles equipped with an internal combustion engine. It is often found in the fuse box located in the engine bay and functions as the primary electronic switch that controls power to the fuel pump. The fuel pump relay is usually controlled by the ignition or Powertrain Control Module, and when switched on, will provide current to the fuel pump so that it may function. As the fuel pump relay controls power to the fuel pump, any faults with it can cause issues with the fuel pump, which can cause drivability problems for the vehicle. Usually a bad or failing fuel pump relay will produce a few symptoms that can alert the driver of the issues.
1. Engine stalls
One of the first symptoms of an issue with the fuel pump relay is an engine that suddenly stalls. If the fuel pump relay has an issue while the vehicle is operating it will cut off power to the fuel pump, which will cause the engine to stall. A faulty relay may allow the vehicle to be restarted a short while later, while a completely failed relay will not.
2. Engine does not start
Another symptom of a faulty fuel pump relay is an engine that does not start. If the fuel pump relay fails the fuel pump will be left without power. The engine may still crank when the key is turned, however it will not be able to start due to lack of fuel. This symptom can also be caused by a wide variety of other issues, so having the vehicle properly diagnosed is highly recommended.
3. No noise from the fuel pump
Another symptom that may hint at an issue with the fuel pump relay is no noise from the fuel pump when the key is switched on. Most fuel pumps will produce a low volume hum or whine which can be heard from the inside the vehicle if listened for closely, or from the outside of the vehicle, near the fuel tank. If the fuel pump relay fails, it will cut off power to the fuel pump which will render it inoperable, and therefore silent, when the ignition is on.
While the fuel pump relay is a very simple component, it plays a very important role in the proper operation of the vehicle. If your vehicle is displaying any of the symptoms above, or you suspect that your fuel pump relay is having an an issue, have the vehicle inspected by a professional technician, such as one from YourMechanic, to determine if the component should be replaced.
This article originally appeared on YourMechanic.com as Symptoms of a Bad or Failing Fuel Pump Relay and was authored by Eduardo Ruelas.