Structure The fuel pump consists of an electric motor, a pressure limiter and a check valve. The electric motor actually works in the oil in the pump housing. Do not worry because there is nothing in the housing that can be ignited. The fuel lubricates and cools the fuel motor. There is a check valve at the port, and the pressure limiter is located on the pressure side of the pump housing with the passage leading to the inlet. Working principle When the rotor disk rotates, the roller is pressed outward by the centrifugal force. Like the rotating oil seal, the rotor rotates and the pump works to suck the fuel from the oil inlet and press it into the fuel system from the oil outlet. When the pump is on, the check valve at the outlet closes, preventing fuel from flowing back into the tank through the fuel pump. The pressure in the fuel line that the check valve maintains is called "residual pressure." The maximum pump oil pressure for a fuel pump depends on the pressure limiter's standard. If the fuel pump pressure exceeds a predetermined pressure limit, the pressure limiter opens a bypass to allow fuel to flow back to the fuel pump inlet.