Before the fuel injection pump starts to supply fuel, the needle valve of the fuel injection nozzle is closed and kept in this state by the spring After the injection pump starts its oil pumping stroke, the high-pressure diesel enters the injection nozzle assembly through the oil inlet pipe connector, and enters the oil chamber around the needle valve pressure cone through the oil passage in the injection nozzle body. When the diesel pressure reaches the set pressure, the upward pushing force of the oil pressure on the needle valve pressure cone will open the needle valve, and the diesel reaches the spray hole from the very small oil chamber called the oil pocket under the needle valve, and sprays out with fine oil mist from these spray holes

When the pump oil pressure decreases, the needle valve spring makes the needle valve fall on the valve seat and the injection process ends