There are many cases of missing the car, but you must have never encountered the fault shared this time. Let’s see how the master can take care of the difficult and miscellaneous problems.
Faulty vehicle:
Guosi Futian times light truck is equipped with quanchai 4b2-95c40 engine Bosch edc17c55 computer board.
There is no fault code when you don’t start the car. You can start the car without stalling by spraying starting fluid. After closing the key door, you can’t start the car again. Communicate with the driver that this is a faulty vehicle transferred from the school pump station. The fuel injector has been adjusted and the rail pressure sensor has been replaced of pressure sensor.
According to the fault phenomenon, we eliminate it step by step, and eliminate the fault of relevant circuit of starter rotation. The engine will not shut down after landing, and timing and mechanical related faults can be eliminated of pressure sensor.
It also shows that the rail pressure can be established when the engine is running normally. The faults of low pressure blockage and high pressure leakage are eliminated accordingly.
Analyze the fault point. It may be that the rail pressure cannot be established quickly during startup, insufficient fuel injection or rail pressure sensor harness.
1. Read the data flow and observe the change of rail pressure during startup. The engine speed of taxi is 205r / min, and the difference between the actual rail pressure of 405bar and the rated rail pressure is very small. From the data flow, the engine speed is not low, and the rail pressure can be established quickly during startup.
Analyze that the engine rotates normally, the rail pressure is normal, the timing signal is normal and the fuel injector is normal. Is it the ECU problem, but it can be stabilized after spraying the starting fluid, which indicates that it is not like ECU fault.
It seems that the fault point is not so simple, otherwise the school pump station will not be solved, and the problem should still be related to rail pressure.
2. When reading the starting data stream again, a phenomenon was observed. After flameout, the actual rail pressure drop could not fall below 143bar, and the sensor signal voltage was 0.52v.
After opening the high-pressure oil pipe, the pressure is still 143bar, which can eliminate the interference of oil circuit. The signal voltage is obviously inconsistent with the pressure value, check the rail pressure sensor harness.
3. Disconnect the sensor harness, measure the voltage, supply 5V, ground 0V and signal wire 3.5V. The signal line voltage is abnormal. At this time, read the data flow rail pressure of 1799bar and the sensor voltage of 2.99v of pressure sensor.
4. Measure whether the signal wire is short circuited to ground, and whether the harness resistance is short circuited or falsely connected.
A phenomenon was observed when reconnecting the harness. The data flow showed that the rail pressure changed from 0bar to 143bar, and the pressure value fed back by the rail pressure sensor was obviously abnormal.
There are two abnormal phenomena: first, disconnect the harness, and the signal voltage is 3.29v; 2、 The rail pressure sensor of the connecting harness cannot normally feed back the actual pressure in the rail.
And the two phenomena point to different fault points and begin to suspect the matching problem between ECU and rail pressure sensor.
5. Query the edc17c55 technical manual and find that the feedback voltage signal range of the supporting rail pressure sensor is 0.3-3v.
At this time, it suddenly becomes clear that it is normal to disconnect the harness and measure the signal line voltage of 3.29v.
The fault point is that the signal fed back by the rail pressure sensor is incorrect.
6. It is found that the fault is not the sensor itself, but the model of the replaced sensor is wrong. The 0281006425 rail pressure sensor used by Weichai is installed, and the feedback signal range of this type of sensor is 0.5-4.5v.
The initial value fed back by the sensor is 0.5V, which corresponds to the standard data flow of edc17c55. Indeed, it should be more than 100bar. Replace the correct matching model 0281006047 sensor and eliminate the fault.
Although only one sensor has been replaced in this fault, it has experienced many twists and turns to find the cause of the fault. The application of detection equipment and the understanding of the principle of common rail system are indispensable.
Bold assumptions and careful observation, especially data flow, are important means to solve difficult and miscellaneous diseases. We should have a sensitive response to any abnormality in order to truly achieve “Heaven’s net is broad” without omission.
Finally, when repairing an electronically controlled vehicle, the replacement of relevant accessories should not only consider the mechanical installation and cooperation, but also consider whether the model is consistent.
Bosch accessories have a standard 10 digit code. Before replacement, be sure to confirm that the model is the same or replaced by accurate supporting information. Otherwise, even if the installation is OK, but the feedback electrical signal is inaccurate, relevant faults will occur.
