The fuel supplied by the fuel injection pump to the injector must have a certain pressure to ensure good atomization of the fuel in the injector. The injection pressure is too low, the atomization is poor, the diesel engine is not easy to start; the fuel consumption rate is increased, the exhaust gas is black smoke, and the lower end of the needle valve body is easy to deposit carbon. The injection pressure is too high, which accelerates the wear of the fuel injection pump and injector parts, and sometimes causes the high pressure oil pipe to burst. If the injection pressure deviation is too large, the diesel engine power will be reduced and the fuel consumption rate will increase.
The main reason for the insufficient oil supply pressure is that after the plunger of the fuel injection pump and the oil-discharge valve coupler wear, the sealing performance is degraded, resulting in a decrease in the injection pressure and causing poor atomization. The reason why the injection pressure is too high and low is artificial adjustment: if some maintenance personnel do not use the instrument for testing, but adjust the injection pressure by experience; if some maintenance personnel observe the spray quality to judge the injection pressure; Listen to the sound of the fuel to judge the fuel pressure; some operators point their hands at the injector to spray the fuel on the hand, judging by the feeling of the palm. These experiences vary from person to person and vary greatly, and the pressure of the fuel supply is not accurate. Some operators also intend to increase the injection pressure, thinking that this can use high-pressure fuel to wash away the carbon deposits in the injector, and can also make up for eliminating the oil drop phenomenon of the injector.