What does an oil pump do? Oil pump manufacturers small make up for you to introduce it:

The pump is generally integrated in the injection pump body, its role is to ensure the diesel oil in the low-pressure oil circulation, and supply enough quantity and a certain pressure fuel to the injection pump. When the fuel pump rotates, the fuel is pumped from the fuel tank into the injection pump body through the water precipitator and fuel filter under the pressure set by the regulating valve. The forms of oil pump are piston type, diaphragm type, gear type and blade type. Gear and vane pumps are widely used for their reliable operation and simple structure.