A fuel pump check valve is a component of a mechanical fuel pump, which is found on many vehicles that were manufactured before electronic injection. A mechanical fuel pump has a two-port check valve, one that is located on the pump’s inlet and one that is located on the pump’s outlet. The check valve is designed to make the fuel in the vehicle only flow in the correct direction from the fuel pump and to maintain pressure. If a fuel pump’s check valve goes bad, it could cause one or more symptoms.
When the fuel pump’s check valve goes bad, it will not be able to maintain the proper amount of pressure, causing the vehicle to run poorly or stall. A fuel pressure gauge can be used to test the amount of fuel pressure when the vehicle is running. If the amount of pressure is lower than the specifications for your car, the check valve may need to be replaced.
If the fuel pump’s check valve is bad, the vehicle may start properly, but stall as soon as the fuel pump turns off. This is due to the lack of pressure, which allows the fuel to flow back into the pump.
If the check valve is bad, the car may be unable to start. If the car does not start, turning the key so that it is one click away from starting, then repeating this process several times, may build up enough pressure so that the vehicle starts. If that is the case, the check valve is bad and needs to be replaced.