The fuel-pump relay unit is responsible for turning the fuel pump on when it detects the engine is running. When the ignition signal stops, the fuel-pump relay switches the pump off. Problems with the ignition and starting the vehicle often can be traced to the condition of the fuel-pump relay.
The fuel-pump relay is a small unit, typically enclosed in a plastic case. The unit contains several sprockets on one side that are clipped onto the ignition system. The fuel-pump relay is engaged only during the start cycle. If it is faulty, it can take longer to start your vehicle.
Most fuel-pump relay units are located under the dashboard near the steering column. In some cases, the unit is located in the area where the steering column is mounted or near the engine’s firewall. The end of the fuel pump relay is typically located near the center of the floorboard, under the carpet in the front section of the passenger's or driver’s side footwell.
In addition to difficulty in starting the vehicle, symptoms of a poorly functioning fuel-pump relay include the following: the car dies then starts a few minutes later; the fuel pump makes a strange noise (humming or clicking loudly) for longer than five to 10 seconds after starting; or the engine won’t start after you have engaged the fuel-pump switch.
When your car does not start properly, you can conduct a fuel-injection relay test. Two relays are located inside the fuel-injection system; one of them is responsible for turning the ignition on without turning over the engine, and the other is responsible for turning on when the engine turns.
You can check to see if the first relay is working by touching it while turning the ignition on and off. You should feel a "click" every time you switch the ignition. If the fuel-pump relay is not working, you can “jump” the unit with a small lead jumper cable. You will need to access the fuse panel and insert the cable into the relay unit; the unit will run as long as the wire is inside the relay and can help start your car.
The fuel-pump relay is not wholly responsible for starting the engine. In some vehicles, the car can start with the oil that remains in the galleys. If the engine is cold and the oil is thick, the vehicle can be started within a few minutes without any assistance from the fuel-pump relay. A light humming noise coming from the gas tank is a sign that the fuel-pump relay needs to be replaced.
- Photo Credit car image by Brett Bouwer from Fotolia.com
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