the injector reaches a predetermined level, the plunger lifts and injection starts. In common rail systems, a high-pressure pump stores a reservoir of fuel at high pressure — up to and above . The term "common rail" refers to the fact that all of the fuel injectors are supplied by a common fuel rail which is nothing more than a pressure accumulator where the fuel is stored at high pressure. This accumulator supplies multiple fuel injectors with high-pressure fuel. This simplifies the purpose of the high-pressure pump in that it only needs to maintain a target pressure (either mechanically or electronically controlled). The fuel injectors are typically controlled by the engine control unit (ECU). When the fuel injectors are electrically activated, a hydraulic valve (consisting of a nozzle and plunger) is mechanically or hydraulically opened and fuel is sprayed into the cylinders at the desired pressure. Since the fuel pressure energy is stored remotely and the injectors are electrically actuated, the injection pressure at the start and end of injection is very near the pressure in the accumulator (rail), thus producing a square injection rate. If the accumulator, pump, and plumbing are sized properly, the injection pressure and rate will be the same for each of the multiple injection events. Third-generation common rail diesels now feature piezoelectric injectors for increased precision, with fuel pressures up to . See also Hydraulically actuated electronic unit injection Turbocharged direct injection Unit pump Water sensor References External links Common Rail Direct Injection System or CRDI System working and advanatages Brief Summary about working of CRDI Engine Animation explaining common rail functioning Diesel engine technology Engine fuel system technology ja:噴射ポンプ#コモンレール式