BMW engine jitter and the smell of gasoline Symptoms: a BMW e66760li sedan, the user reflects the engine idling jitter, driving in the acceleration, the recent emergence of the engine after the start of the smell of gasoline.
    BMW engine jitter and the smell of gasoline troubleshooting: pick up the car, the maintenance staff first to the user to understand the car before and after the emergence of abnormal circumstances. Users reflect that some time ago because of the local typhoon causes, causing this car part of the water. At that time the water treatment did not appear after the failure, after a period of time there have been a variety of failures, but then most of them are repaired, only the engine failure has not been repaired. Cleaning the throttle in other repair shops, replacing the ignition coil and spark plugs did not solve the problem.
    This car is equipped with a n73 engine, which is a highly technical engine, 12 cylinders were v-shaped arrangement, each cylinder 4 valves, using the electronic valve full variable valve control technology (valvetronic) and fuel injection technology.
    N73 engine fuel direct injection system, the injector nozzle is located in the combustion chamber, close to the intake valve, each cylinder of the injector installed in the same oil track. The oil cylinders of each column are supplied with high pressure fuel from a high pressure pump, which is driven by the exhaust camshaft. The high-pressure pump will pressurize the fuel from the electronic fuel pump, so that the fuel pressure increased to 5 ~ 12mpa, the compressed fuel through the high-pressure tubing to the oil rail, and then to the injector, the injector by the dme engine control unit according to the relevant sensor Signal to control. Because the fuel pressure after pressurization is very high, conventional fuel pressure gauges can not be used to measure the fuel pressure of high-pressure pipelines in general repair plants. And from the maintenance manual can be seen, the fuel injector control voltage between 85 ~ 100v, so the general car oscilloscope is difficult to use here to measure, fuel injection time can only use the fault diagnosis device to view.
    First connect the BMW original fault diagnostic software gt1, select the menu in the 7 series e65 project (because the gt1 menu does not provide e66 project, e66 and e65 only long axis models and short axis models of the points), fault diagnosis machine automatically identify the model Into the whole car electronic control system detection, detection of a lot of fault code, because it can not identify the true and false fault, so record the fault code after all cleared. This car has two dme engine control unit, dme-1 is 1 ~ 6 cylinder engine control unit, dme-2 is 7 ~ 12 cylinder engine control unit, in the query dme-1 fault code shows 2 cylinder bad The fault code, clear the fault code and then start again, the fault code again.
  The main data are as follows: air flow signal 15kg / h; oil rail pressure 3.0mpa; fuel injection time 1.89ms; acceleration pedal signal 1 is 0.72v, accelerator pedal signal 2 is 0.36v. Comparing with the standard data stream, it is found that the air flow signal is slightly larger and the fuel injection time is longer. Continue to view the data flow found the problem, 2 cylinder operation instability value has reached 5.10, while the other cylinder value is close to 0, indicating that 2 cylinder obviously poor work. The engine on the right side of the intake hose removed to see the 2-cylinder ignition coil is also affixed with a very new label, which shows just changed, for the sake of reliability, maintenance personnel and replaced a normal work of the ignition The coil and the spark plug are tested and the result is that the 2-cylinder is still not working (in this case, the maintenance personnel are required to be aware that the maintenance personnel are often experiencing some of the new refueling coils that are replaced when repairing the BMW). Continue to use the fault diagnosis instrument to detect the dme-2 engine control unit, which stores the 8-cylinder bad operation of the fault code, the data stream can be seen from the 8-cylinder operation of the unstable value has reached 1.93, check the 8-cylinder ignition coil and Spark plug is just changed.
    Depending on the experience of maintenance, the cause of the overall engine failure may involve multiple systems, but the cause of one or more cylinders does not work. First analysis of the fuel system, because the fault on the instrument shows the oil rail pressure of 3.0mpa, indicating that the pressure is normal, and should not appear individual cylinder oil pressure is too low, the injector by the engine control unit control work, the engine control unit The probability of the problem is very low. On the other hand, if there is a problem with the injector line of the individual cylinders, the system should store the fault code of the injector line short circuit or open circuit. As for the ignition system, the BMW car ignition system control line work is relatively stable, very few problems, but the ignition coil and spark plug sometimes problems, and maintenance personnel with a test light to detect the 2-cylinder ignition line part, start When the engine test light can flash, indicating that the ignition line is basically normal.
    The cylinder pressure should be checked next. If the vehicle does not disassemble the intake manifold, it can not measure the cylinder pressure, but the user is concerned that the maintenance personnel are not familiar with the structure of the engine. There is no gasoline at the time of starting. Since the fuel pipe has been removed at the time of inspection, Gasoline smell, so decided to check the next day. The next morning, start the engine, there are some gasoline flavor, but look at the external tubing and did not find the place to leak, if there is leakage should be under the intake manifold tubing oil spill. Because the maintenance personnel on the structure of the n73 engine is very understanding, you can determine if you do not remove the intake manifold can not continue to check the fault, so convince the user to allow the demolition of the engine intake manifold. After removing the intake manifold, it was found that the fuel lines between the two rows of cylinders had some oil leakage (Fig. 4), but not serious. Why is the oil pressure leaked on the fault of the tubing or the fuel pressure is normal? Maintenance personnel that should be leaked very little, high pressure pump pressure compensation, so the data stream did not see the problem.