The role of the automobile metering unit is to control the oil intake and return flow of the high-pressure oil pump, thereby controlling the oil supply of the oil pump plunger to the rail, meeting the set pressure of the common rail system, and forming a closed loop control of the rail pressure with the rail pressure sensor. The internal structure of the fuel metering unit is not complicated. It consists of three parts: a housing with an electromagnetic coil, an upper cover with an oil hole, and a valve core that can move up and down. When it is damaged, just replace it with a new one.