故障现象一辆2012年生产的福建奔驰凌特车,搭载OM 651柴油发动机,累计行驶里程约为4.5万km。车主反应,该车发动机无法起动。故障诊断接车后试车,起动发动机,起动机运转正常,但发动机无法起动着机。用故障检测仪(DAS)对车辆进行快速检测,发动机控制单元(CDI)和点火开关(EZS)中均无故障代码存储。诊断至此,推断燃油供给系统存在故障的可能性较大。该车燃油供给系统由低压回路和高压回路(图1)组 Symptom A 2012 Fujian Mercedes-Benz Sprinter, equipped with OM 651 diesel engine, has a cumulative mileage of 45,000 km. Owner response, the car engine can not start. Troubleshooting Car after the test run, start the engine, the starter is operating normally, but the engine can not start with the machine. The vehicle is quickly tested with a DAS, and no fault codes are stored in the engine control unit (CDI) and ignition switch (EZS). At this point of diagnosis, it is inferred that there is a high probability of a fault in the fuel supply system. The car fuel supply system consists of low-voltage circuit and high-voltage circuit (Figure 1) group