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. No noise from the fuel pumpĪnother 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. This symptom can also be caused by a wide variety of other issues, so having the vehicle properly diagnosed is highly recommended. The engine may still crank when the key is turned, however it will not be able to start due to lack of fuel. If the fuel pump relay fails the fuel pump will be left without power. Engine does not startĪnother symptom of a faulty fuel pump relay is an engine that does not start. A faulty relay may allow the vehicle to be restarted a short while later, while a completely failed relay will not. 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. One of the first symptoms of an issue with the fuel pump relay is an engine that suddenly stalls. Usually a bad or failing fuel pump relay will produce a few symptoms that can alert the driver of the issues.

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. 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. 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 an electronic component that is found on virtually all vehicles equipped with an internal combustion engine.

2005 expedition fuel pump relay