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What to do if the engine is difficult to start?

Views:33     Author:Site Editor     Publish Time: 2020-09-30      Origin:Site

Regarding the failure of the engine to start difficult, our troubleshooting directions are as follows.


Troubleshoot points


Fuel injector failure, such as too small fuel injection at idle point.


Sensor problems, such as water temperature sensor and intake air temperature sensor signal drift, resulting in low idle fuel injection, etc.


Intake and exhaust pipelines, if the intake and exhaust are blocked, the engine intake is not smooth, etc.


Cylinder's airtightness, such as poor sealing of inlet and exhaust valves, failure of exhaust brake in cylinder, failure of piston ring, etc.


Fuel pipeline problems, such as leaks in the fuel pipeline, causing air to enter the high-pressure pipeline.


Synchronization timing problems, such as single-speed sensor starting, abnormal synchronization signal, etc.


Computer board ECU problems, such as abnormal data, ECU electrical aging.


Troubleshooting steps


Use the decoder to read the fault code. If the decoder shows that the system is normal, there is no fault code.


Use the decoder to read the data stream. If there is no abnormality, the target rail pressure is equal to the actual rail pressure, and the fuel metering unit value is normal. It is preliminarily judged that there is no problem with the oil circuit; check whether the synchronization data stream is normal and judge whether there is any problem with the synchronization timing .

If there is no problem with the fault code and no problem with the data flow, the troubleshooting direction of the fault can be further focused on the air tightness of the cylinder.


When idling, seeing the data flow of the fuel metering unit bounce back and forth in a relatively large range, it can basically be determined that the fuel metering unit is stuck.


Use a cylinder pressure gauge to measure the airtightness of the cylinder, and use a cylinder pressure gauge to measure the cylinder pressure of each cylinder. If there is not much difference, it means that the airtightness of the cylinder is good and eliminate the airtightness problem of the cylinder.


If there is no problem with the air-tightness of the cylinder, and the data stream and fault code can not be found, we will place the troubleshooting direction on the injector in the next step.


Remove the fuel injector, use the bench to measure the fuel injection volume of the fuel injector at each point, and see whether the data shows whether the fuel injection volume of the fuel injector is normal.


Next, use an oscilloscope to collect the synchronization waveform to further determine that there is no problem with the synchronization timing.


If after the previous investigation, the reason for the engine's difficulty in starting is not found, first remove the injector from the engine and install a test light on the injector to see if the fuel injection and electric injection conditions are normal.


If there is basically no fuel output for a few seconds before the start of the taxi, but the fuel injector test light is flashing, and the fuel is slowly discharged over time, the vehicle starting may be caused by the failure of the rail pressure. In order to check whether it is caused by the slow rise of rail pressure, a mechanical nozzle can be connected. Adjust its pressure to 300bar and observe whether there is a delay in its injection time. If the external mechanical nozzle is connected, it is found that the injection time delay of the mechanical nozzle is eliminated. Then there is no problem with the injector. The mechanical nozzle is not powered on, and when the pressure is reached, it will start to inject; for the electromagnetic injector, not only the pressure is required to be higher than 200bar, but also the ECU needs to be powered on to inject fuel.


Finally, check the ECU program and ECU hardware.


Decoder flashing, use the decoder to flash the program. After the flashing is completed, if the fault persists, replace with a new ECU, and the engine will no longer have difficulty in starting.


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