Role of Fuel Pump Relay (FPR) in Fuel Delivery System in an Automobile

Ellen T. Kohler
Oct 2 · 2 min read

As a vehicle owner, you need to be aware of 12v fuel pump relay, a critical component of an automobile’s fuel delivery system. Its basic function is to control the operation of the fuel pump — it supplies electrical power at ignition and switch off.

Also called relay switch, it is a small electrical device located in a plastic casing under the hood, on the firewall or near the vehicle’s steering column. The location may differ, because for different cars, it is located in different places. You can check your owner’s manual for the exact location of the FPR.

FPR is controlled by Engine Control Module (ECM)
The engine control module, also known as powertrain control module (PCM), is the central unit of the engine management system of a vehicle. It controls the generation and supply of air fuel mixture, ignition timing, idle speed, variable valve timing and emissions that are necessary for the engine to run. The Engine Control Module also controls the FPR when the fuel pump is on. In short, Engine Control Module (ECM) performs many functions that are necessary to operate a vehicle.

Starts the fuel pump and shuts off when engine starts running
The FPR supplies electricity to startup and shutdown the pump of the vehicle. When the ignition is turned on, the FPR is activated. The relay supplies power to the pump, which becomes active and lets out the fuel that is necessary for the vehicle to run. When the vehicle is turned on and is running, the FPR shuts off, and the current to the pump is supplied by the oil pressure sending unit. Without the FPR, the process of fueling the engine will not begin.

Replace faulty FPR immediately
If the engine is cranking, but not starting, it could be an issue with the FPR. This is because the FPR is not turning-on the pump to start the vehicle. It is better to check with a mechanic.

You need to make sure that your vehicle’s FPR is in good condition so that it does not overload the fuel pump. A fuel pump handles a significant amount of power but if it receives too much power at once, it can get damaged — the wiring around it is very delicate. Fuel pump is be an expensive part to replace. So, it is advisable to get the relay inspected, and replaced if it is damaged immediately.

Ellen T. Kohler

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