When the engine is running, the engine suddenly accelerates and the fault lights alarm.
  • Automotive

A Volkswagen ten meter car with a mileage of about 103 thousand km in 2012. Users reflect: during the driving process, the engine suddenly fails to accelerate and the engine fault lights alarm. Inspection and analysis: maintenance personnel first test run, found engine fault lights alarm, and engine maximum speed can only reach 3000 r/min. Connect the fault diagnosis instrument VAS5051 to detect the engine control unit, get the following fault code: 08851 - fuel pressure regulating valve N276 mechanical failure. The maintenance personnel comprehensively analyze the above failure and fault code, and use VAS5051 to read the working oil pressure of the engine running, and find that the value of the 01-08-140-3 area is 700 kPa, the result is not normal. This value should be around 4 MPa at idle speed. It is obvious that the high pressure fuel supply system of the vehicle is not working properly. High pressure oil supply system without high pressure reasons are mainly the following possibilities. (1) low pressure fuel system pressure is too low, resulting in insufficient intake of high pressure oil pump, resulting in high pressure system oil pressure is too low. (2) fuel pressure regulating valve N276 failure, resulting in failure to establish normal high pressure (idle speed around MPa). (3) the mechanical fault in the high pressure pump causes the blockage in the high pressure pump and can not set up the high pressure. According to the fault code and fault phenomenon of the vehicle, it is preliminarily judged that the fault point of the vehicle is the N276 fault of the fuel pressure regulator, which causes the high pressure fuel pressure to be too low and the acceleration is weak. But in order to distinguish between the N276 regulating valve circuit failure or the mechanical failure, the maintenance personnel use VAS5051 to do the following component function test to the N276: enter the engine control unit 01, select the function 03 a component test, and select the fuel pressure regulator N276 solenoid valve, at this time the N276 solenoid valve can hear the "Da Da" sound. At the same time, the N276 solenoid valve is touched by hand. After checking, the N276 solenoid valve of the fuel pressure regulator works normally. At this point, the fault point is locked on the high-pressure pump of the fuel system. (Note: when checking the N276 solenoid valve for the fuel pressure regulator, the N276 solenoid valve is prohibited to continue to pass through the positive electricity, otherwise the N276 solenoid valve will burn out immediately, and the N276 solenoid valve can only be checked with the diagnostic function of the VAS5051 and other diagnostic instruments.) Troubleshooting: replace the engine fuel system high pressure pump (and fuel pressure adjustment valve N276 integrated together) after the test, everything is normal, read high pressure oil supply system fuel pressure of about 4 MPa, troubleshooting. Summary: the typical fault phenomena of the engine oil high pressure system failure include: engine fault light alarm, high pressure system fuel pressure is insufficient; the engine maximum speed can only reach about 3000 r/min; engine control unit memory N276 or N276 mechanical fault code. Due to the damage of the fuel pressure regulating valve caused by the gasoline quality, the fuel filter must be replaced and the oil way should be replaced at the same time when the fuel pressure regulating valve is replaced.