A fuel pump relay directs power to the electric fuel pump, preventing overheating. It’s located under the hood, and turning the key to the on position can test it. If it’s faulty, it’s easy to replace.
A fuel pump relay is an electrical device much like an automotive fuse. It directs power to the electric fuel pump and ensures that the part receives enough power to function properly, but not enough power to damage it. Fuel pumps require a lot of power to run and this could cause the pump and wiring system to overheat if it weren’t for the relay.
In most cars, the fuel pump relay is under the hood of the vehicle and connected to the firewall. It’s a small black plastic box with a wire harness plugged into the bottom. The relay functions as a monitor for power to the fuel pump, turning it on when the ignition is turned on, and turning the pump off when the vehicle is turned off. The hum of the fuel pump can be heard when the ignition switch is first turned to the on position. This provides fuel for the vehicle to start, and once the vehicle is running, the vehicle’s computer sends a signal and the fuel pump relay turns off. The vehicle’s fuel pump will now be powered via another source, typically the oil pressure sending unit.
To test the relay in the event of a vehicle that won’t start, drivers can turn the key to the on position and listen for a hum or hum coming from the vehicle’s fuel tank. If there is no noticeable sound, the problem could be the fuel pump or the relay. It is much easier to test the relay than to change the fuel pump.
On most vehicles, there will be two or more relays in the same location. Most are the same, and the vehicle’s owner’s manual will provide information on where they are. A driver can disconnect the relay to test if it is causing a problem. If there is another relay next to it, you can disconnect it and plug in the fuel pump wiring harness. You should then turn the vehicle key to the on position and again hear the sound of a running pump.
If the pump works, it’s time to buy a new relay at the auto parts store. If the pump still does not work, the driver should check the fuel pump. This will require removing the fuel tank. People should exercise caution when working with fuel and make sure to keep the work area clean to avoid accidents.
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