The electronically controlled fuel injector is the most critical and complicated part in the common rail system, and also the most difficult part in design and technology. By controlling the opening and closing of the solenoid valve, the ECU sprays the fuel in the high-pressure oil track into the combustion chamber with the optimal injection timing, amount and rate. In order to achieve effective injection starting point and accurate injection amount, common rail system adopts special injector with hydraulic servo system and electronic control element (solenoid valve).

The injector is composed of a hole nozzle, a hydraulic servo system (control piston, control hole, etc.) and a solenoid valve, which are similar to traditional injectors.