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Bmw maintenance is fast and fast
(b) in case of failure: after taking over the vehicle, the writer first asked the user whether the vehicle had an anomaly before or after the malfunction. Users indicated that the vehicle had been partially watered during the previous period because of local typhoons. The water was cleaned and no malfunctions occurred, and after some time in use, a variety of malfunctions occurred, but most of them were subsequently repaired and only the engine malfunctions remained unrepaired. The clean-up of gas-saving doors in other repair plants and the replacement of fire wire rings and spark plugs did not solve the problem。
The vehicle carries the n73 engine, which is a highly technical engine, 12 cylinders organized in a v-type structure, four gas doors per tank, using electronic gas doors for all variables (valvetronic) and direct oil jet technology。
The fuel jet system of the n73 motors, the nozzles of the jets are located in the combustion chamber, close to the gas entrance, and the oil dispensers of each cylinder are installed on the same oil track. Each tank tracks provide high pressure fuel from a high pressure pump driven by an exhaust cam axis. High pressure pumps pressurize fuel from electronic fuel pumps, increasing fuel pressure to 5-12 mpa, compressed fuel reaches the oil track through the high pressure pipeline and then reaches the jet, which is controlled by the dme engine control unit according to the signal of the relevant sensor. Because of the very high pressure of the pressurized fuel, conventional fuel pressure sheets cannot be used to measure the pressure of the high pressure pipe at the general maintenance plant. Moreover, it is known from the maintenance manual that the control voltage of the jets is between 85 and 100 v, which makes it difficult for general vehicle oscilloscopes to be used here to measure the time of the jets, which can generally only be viewed with a malfunction diagnostic device。
The first link to the bmw malfunction detector gt1, with the selection menu of seven e65 items (because e66 items are not available on the gt1 menu, e66 and e65 are only divided between long-axis and short-axis models), the failure detector automatically identifies the vehicle and enters the entire electric control system and detects a number of fault codes because it is not possible to identify a genuine or a false failure, so that the failure code is cleared. The vehicle has two dme engine control units, dme-1 is an engine control unit for 1 to 6 cylinders, and dme-2 is an engine control unit for 7 to 12 cylinders, which displays a malfunction code for 2 cylinders when searching for the dme-1 failure code, and starts again after the failure code has been cleared。
The main data are as follows: air flow signal 15 kg/h; oil track pressure 3. 0 mpa; fuel jet time 1. 89 ms; acceleration pedal signal 1 is 0. 72 v and acceleration pedal signal 2 is 0. 36 v. Comparison with standard data streams revealed a slightly larger air flow signal and a slightly longer fuel jet. Continuing to look at the data stream revealed problems, with the operating instability of 2 cylinders reaching 5. 10 (figure 2), while the value of other cylinders was close to 0, suggesting that 2 cylinders were clearly not working well. Dismantling the right of the engine's in-gas hose and seeing a very new label on the two-barrel fuse ring suggests that, for the sake of reliability, the author has replaced a normal working ignition ring and spark plug to test it, and as a result the two-barrel is still not working. The maintenance staff need to be reminded of the fact that, while repairing the bmw, penrs are often confronted with new ignition rings that have been replaced by some repair plants. The dme-2 engine control unit, which continues to be tested using a malfunction diagnostic device, has been stored with a malfunction code of eight cylinders, which can be seen in the data stream as having reached 1. 93, as well as a new fuse ring and spark plug for the inspection of eight cylinders。
Based on maintenance experience, the reasons for the overall malfunctioning of the engine may involve multiple systems, but there should be few reasons why one or more cylinders are not working. The first analysis of the fuel system, since the oil track pressure shown on the malfunction diagnostic instrument is 3. 0 mpa, indicates that the pressure is normal and that there should be no low pressure in individual cylinders, the jet is controlled by the engine control unit, and the engine control unit has a low probability of having problems. On the other hand, if there is a problem with the oil dispenser line in the individual cylinders, the system should store the failure code for short or broken circuits. With regard to ignition systems, the bmw system's ignition circuits are relatively stable, with few problems, except that there are occasional problems with the firing wires and spark plugs, and that peners use test lights to detect the two-cylinder ignition lines, which can blink when the engine starts. This suggests that the ignition circuits are basically normal。
It's time to check the gas tank pressure. The vehicle could not measure the pressure of the cylinder unless it was removed, but the user feared that the maintenance staff would not be familiar with the engine structure and would not allow it to be removed. The author recalls that the user said that there was a petrol smell when it started, that since the fuel pipeline had been removed at the time of the inspection, it already had a heavy petrol smell, and decided to check it again the following day. In the early morning of the following day, the start-up engine did smell of gasoline, but it did not find any leaks in the external pipeline, which, if any, would have leaked. Because the author had a good understanding of the structure of the n73 engine, it could be determined that it would not be possible to continue to check the malfunctions unless the tubes were removed, and the user was persuaded to allow the engines to enter the tubes. Following the removal of the gas tubes, it was found that the fuel pipelines between the two cylinders were impregnated but not serious. Why is the fuel pressure shown on the malfunction diagnostic device from the pipeline still normal? The author believes that the leak should be minimal and that the pressure is compensated by the high pressure pump, so there is no problem from the data stream。
There should be other reasons for the glitch because the engine was glittering before the car smelled gasoline. Since only two cylinders are not working well, components such as air flow meters, oxygen sensors and water temperature sensors do not need to be checked, but rather should focus on whether there are leaks and tank pressures。
At this point, the author is aware that there is one rotor case in which the exhaust gas cycling tube is not plugged, which leads to a lack of speed in the engine, a situation that is not easy to detect unless the gas can be removed. The pressure of each tank was measured to be normal, and the sealing of the entry tubes in the two and eight cylinders was checked. Although the fixed bolts of the entry tubes were tight, a slight leak could be seen from traces of the pressure of the cavities。
Replacement of leaked fuel pipelines, installation of exhaust gas circulation tubes and replacement of gaskets, start-up engine, all values are normal as shown in the data stream of the fail detector, and the test vehicle was completely eliminated. During the subsequent maintenance work, several cases of bmws, including 745i vehicles carrying n62 engines, were discovered by the author because of leaks in gaskets that caused the engine to tremble, hoping that the maintenance staff would be alerted。
Summary: although the vehicle was a result of multiple malfunctions caused by several malfunctions, the direct cause of the failure of the two and eight cylinders was the leakage of gaskets, which would have been easier to remove if the failure had occurred on the usual pattern. However, in the case of engines using a direct jet system, former maintenance staff were afraid to conduct dismantling inspections because they were not familiar with their working principles or the specific structure of the n73 engine, thereby losing the opportunity for troubleshooting, while at the same time creating mistrust among users of the maintenance staff. This failure has given rise to reflection by the writer, who suggested that maintenance staff should focus not only on learning about vehicle electrical control systems, but also on learning about the dismantling of specific mechanical structures, which would otherwise be prone to failure。
