Fault 1:
    A Passat B4 driving 170,000 km after the hot car is not easy to start, high speed ramp phenomenon. According to the driver to reflect, in order to rule out the failure, the car in other garage has been replaced by air flow meter, distributor and cylinder line, but the failure did not improve. Users said that because the maintenance staff with VAG1552 test proposed two fault code, so the replacement of the air flow meter and distributor.
    After repairing the car, according to their own independent EFI car repair diagnostic ideas, step by step careful analysis and judgment. First detected with tail gas analyzer exhaust, found that the engine idle when the CO content of 1.9%, HC content of 200ppm. CO and HC at the same time significantly exceeded the measurement results to determine the initial point of failure should be in the ignition system. First check the ignition advance angle with the ignition timing tester and find that the engine idling speed is 25 °, and it is confirmed that the intermediate axis timing mark is different from the standard position by two teeth. The cause of the malfunction may be caused by the improper assembly of the mechanic at the time of replacement of the distributor. In the use of ignition waveform analyzer inspection, found that the secondary waveform breakdown voltage and flashover voltage is much lower than the standard value. But the measurement of ignition coil operating voltage and resistance values ​​are in line with the standard.
    Through the above measurement to determine the replacement of the ignition coil, in exchange for the original car air flow meter and distributor, correct the ignition timing, the fault completely ruled out.
    Modern car repair can not only rely on the original traditional experience by replacing the accessories to solve, only the modern car technology completely thoroughly, the use of indispensable detection equipment, the correct analysis of test data in order to quickly and accurately troubleshooting.
    Fault 2:
    When the owner starts the vehicle in the morning, the engine starts up hard. Try to start the car after trying many times. Hot car parking for some time to start, still very difficult.
    From the fault point of view, the problem should be out of the fuel supply system. After the engine has stopped working, in order to be able to make the next start a smooth start, the fuel supply system must ensure that there is enough oil and oil pressure. Therefore, in the oil supply pipeline is equipped with an accumulator or check valve to ensure the normal start of the engine. If the oil is too small or the oil pressure is too low, the engine will appear difficult to start the phenomenon.
    Turn off the ignition switch, in the oil pipe connected to the fuel pressure gauge, clamped back to the tubing, start the engine, running for some time after the engine flameout. I saw the fuel pressure gauge pointer in a very short period of time almost zero, indicating that the fuel supply system can not hold pressure. The car's petrol pump just changed in other repair shop, generally do not have any problems. In addition the car as long as the start, work everything is normal, indicating that the nozzle will not be blocked, needle valve stuck situation. Carefully check the oil, from the fuel tank to the fuel distribution pipe, and then to the return pipe, did not find any parts of the phenomenon of leakage.
    Again and again, think the problem is still out on the fuel pump. Because of the car's one-way valve, petrol pump pump core for the integrated design, the fuel system has a holding effect. Although the petrol pump is new, but there may still be problems. So from the same type of car to remove a gasoline pump into the original car, the replacement of the pump can be fully operational. But the original car after the petrol pump installed, is still not easy to start, can not help but into confusion.
    After careful consideration, think of this car petrol pump is installed in the tank, from the petrol pump exports to the tank out of the tubing pipe between a transparent rubber tube, when the removal of the petrol pump, did not see the traces of rupture. In other pipelines or components are under normal circumstances, in order to confirm the failure, may wish to remove the petrol pump again check.
    Remove the gasoline pump outlet and the fuel tank between the tubing connector after the rubber tube, and finally found the cause of the malfunction! Blocking the end of the tube, at the other end of the mouth blowing, and found that this tubing really leak. This section of about 15cm transparent rubber tube, in the tank after a long period of gasoline soak, has been aging was brown, with the naked eye is difficult to find cracks.
    As the tubing leaks, the engine stops - after a period of time, almost all of the remaining gasoline in the tubing is returned from the leak to the tank, and the oil supply pipe can not guarantee sufficient supply pressure. When the parking time after a car, the engine is difficult to start. After several starts, the petrol pump continuously pump oil, until the pressure inside the oil pipe gradually increased to the normal supply pressure, the engine can start.
    Replace a tubing, the pump installed test drive, cold car can be a hot start, the fault finally ruled out.
    In the process of excluding this failure, before and after a total of 2 times the petrol pump, the cause of the fault is in a small inlet tube, and not on the petrol pump!
    As a maintenance personnel, in the fault diagnosis must be careful analysis of the causes of failure, a comprehensive consideration of the relevant system may have failed parts, in the replacement or repair before thinking, otherwise it is likely to give users loss and trouble. Only by combining the professional theory of the system with the rich practical experience to diagnose the fault, the maintenance level can be improved.