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On average, the cost for a Mercedes-Benz S420 Fuel Pump Relay Replacement is $142 with $47 for parts and $95 for labor. Prices may vary depending on your location.
Every time you turn on the ignition of your car, you activate the fuel pump relay. This device sends an electric current to the fuel pump. Upon receiving this current, the fuel pump sends gasoline to the engine and the car starts running. While the fuel pump is active as long as the car engine is running, the fuel pump relay works only at startup and when you turn off the ignition. As long as the car is running, the fuel pump runs on the power it receives from the oil pressure sending unit or any other such power source.
The fuel pump relay is also called the relay switch and its functions are similar to those of the automotive fuse. Controlled by the engine control module, the fuel pump relay controls the current sent to the fuel pump. This device is a black plastic component, set in a small box with a wiring harness attached to its underside. Its sprockets attach to the engine assembly. Depending on the make of the car, you will find the fuel pump relay under the hood or under the dashboard, near the steering wheel of the car.
The fuel pump of the car is an expensive device that functions well with the optimal amount of current. If it receives excessive power, the wiring system around the pump overheats, and the fuel pump could get damaged or fail completely. The fuel pump relay has a limited lifetime so you should have our expert mechanics check it every time your brakes are changed.
If the fuel pump relay does not work properly, it will not activate the fuel pump and you car will not start. Further, a malfunctioning fuel pump relay could conduct too much power to the fuel pump and cause damage to or ruin it completely. This is why we recommend that you keep the fuel pump relay in perfect working order at all times.
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