How Does a Fuel Pump Operate?

Understanding the types

  • How a fuel pump functions may seem like a terribly complicated subject to understand, but in reality, it's pretty simple. There are, however, a couple of different types of pumps that operate a bit differently from one another. The first type of fuel pump is called a puller pump, while the second type is called a pusher pump. Pumps that are considered to be mechanical fall into the puller category. This means that they have a suction ability that is strong. This ability allows the pump to extract gasoline from a vehicle's tank and push it into the engine. Keeping pressure within the fuel line is easy for puller pumps because the distance between the carburetor and the pump is pretty short. In contrast, pumps that fall into the pusher category are not very good at drawing the fuel; however, they are good at pushing the fuel through the fuel line. Electric fuel pumps are usually considered to be pusher pumps, so their location is close to the fuel tank because in order to get fuel, they depend on a siphon.

How it works

  • The pump also contains what is referred to as a "lever arm." In order for the lever arm to operate, the camshaft of the vehicle has a piece attached that's function is to operate the lever arm of the pump. A diaphragm is also part of the functioning parts of a fuel pump. When the camshaft does a complete 360-degree rotation, the diaphragm also does a complete rotation. This results in the diaphragm moving up. When this happens, the gasoline above the diaphragm will become pressurized and will move from the pump, to the fuel line and then into the carburetor.

Other facts

  • One would think that because the gasoline can flow into the fuel line, it would also flow back down to the diaphragm, where it came from; however, there is a way to keep this from happening involving one-way valves. As the diaphragm goes back into its original position, valves that are located in the body of the pump keep the fuel from going back down into the diaphragm from the carburetor. These one-way valves also make it possible for the fuel to be siphoned from the gas tank by creating a path. As the diaphragm moves, a vacuum is created. This action pulls gasoline into the chamber, with the aid of the siphon.