Inspection and analysis: maintenance personnel commissioning, found that the starting machine can rotate, the oil pressure is normal, spark plugs also jump fire, but the engine has no signs of starting. According to this phenomenon, the fuel supply system of the vehicle is no problem, and the power supply of the engine control system is no problem. The engine control unit is detected without any indication of the inlet fault. Check the intake line, nor do you notice any abnormalities. The fuel injector is more likely to be broken at 4 times. Continuing the trial run, it was found that the engine could start occasionally, indicating that the fault might be due to poor contact. Check the ignition switch and the main relay according to the circuit diagram, without any exception, the fuse is normal. Connect the engine control unit connector adaptor to measure the connection between all electronic components and control unit. Judging from this, the problem of poor contact is likely to be inside the engine control unit. Troubleshooting: replace engine control unit, repeat trial run, failure no longer appear.