The fuel pump on a tractor is a mechanical device, electrically driven, that draws fuel from the tractor’s fuel tank and pumps it under pressure to the tractor’s engine. Diesel fuel is a relatively thick liquid, and the pump must apply enough force to push the fuel through a filter through lines and into the cylinders of the engine at a pressure that enables the injectors to properly atomize the fuel for efficient burning.
Piston-type fuel pumps are relatively simple devices which employ gears to drive a piston assembly. The piston draws the fuel into a chamber, and then the piston moves to compress and force the fuel out through the discharge fitting and then to the engine.
The pressure produced by the fuel pump is adjustable, in order to accommodate the different requirements of various engines. It is adjusted by altering the tension of the spring which acts to return the piston to the draw position.
On tractors with diesel engines, a priming device is required to provide the initial suction to fill the fuel lines to the fuel injection pump. There are two main types of priming systems: hand-priming devices, which are usually hand-operated using a knob or other type of lever, and fuel lift pumps.
Fuel lift pumps are gear driven off of the accessory drive system and are electrically actuated or are used in an engine driven type. The pump is used to pressurize the inlet to the primary pump, which helps in cold starts and improves fuel priming when the engine is running.
