How an Electric Inline Fuel Pump Works

A grey SUV

An electric inline fuel pump is a clever, modern version of the old mechanical pump. The fuel pump is responsible for retrieving the fuel— gas, Diesel, vegetable oil - from the tank and delivering it to the combustion chamber, so you can start your car or truck and keep it running. Mechanical pumps are sufficient to feed fuel into a carburetor. Today however, most engines have an electronic fuel system, and this requires the fuel to arrive at the fuel injector at a more highly pressurized state, to reach necessary combustion ratios. To make this happen accurately and consistently, the electric fuel pump was created.

When you turn the key to the “ON” position, an electric signal is sent to the pump which tells it to begin building pressure on the fuel resting inside it. When the key is turned all the way over to start the engine, the pump sends the pressurized fuel down the line to be ignited.

What Happens Inside the Pump

A fuel pump is actually comprised of several pumping systems inside the small canister-shaped container, which is about the size small jelly jar. First in line is the fuel feed pump, which works like a vacuum to suck the gas or Diesel in from the tank. The fuel is filtered through a mesh screen to block any tank residue, and is then fed into a metering pump, where plunger-like mechanisms push-pull, spin and jostle the liquid to create required pressure.

Once the fuel has been pressurized to precise calculations, it is pushed it out of the pump, down through the fuel line to the fuel rail. From there, a tiny nozzle sprays a fine mist of fuel into the air intake chamber of the cylinder. A spark plug fires and the fuel ignites, and the force provides energy to push the pistons.

Where the Electric Inline Fuel Pump Goes

Historically, these pumps were placed inside the fuel tank. This strategy helped reduce the potential for fire from extreme heat or spark, because gas and Diesel are both cool in liquid form and do not explode. On the downside however, if you were running low on fuel, or cornered sharply, the flow of fuel into the pump might be interrupted, and this could not only cause your vehicle's engine to sputter, but might also damage to the pump itself.

Fortunately, technology has advanced and the inline fuel pump was developed, which can safely be placed outside the fuel tank. However, because it is kept cool by the fuel passing through it, a constant stream of fuel must be maintained. Balance and stress sensors insure that if the pump becomes clogged or damaged, or if the vehicle is in a collision, the pump shuts off, cutting off fuel to the engine and killing it.