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Why the diesel common rail engine is unable to start?

- Aug 23, 2018 -

Why the diesel common rail engine is unable to start?

Rail pressure can not be established (starter is normal, but unable to start).

Common rail system requires high fuel line, low pressure oil line (tank - coarse filter - fine filter, return oil), high pressure oil line (high pressure oil - Common Rail - high pressure oil pipe - injector) must be sealed. Any link out of question, the rail pressure can not be established normally, prompting the main engine plant to the entire fuel line attach great importance.

Note: for the first time, the exhaust and oil filling of the low pressure oil circuit and the high pressure oil circuit must be carried out.

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Check if oil level is too low.

Check whether the hand pump is working normally.

 

Check the low-pressure oil line whether there is gas, side by side air (sometimes low-pressure oil leakage is not obvious, need to be carefully checked).

 

Exhaust method: mainly drains the air inside the filter. Loosen the bleeding bolt on the coarse filter and press the hand pump on the coarse filter manually until the oil continues to flow at the bleeding bolt.

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2) rail pressure can not be established (starter is normal, but unable to start).

If the diesel engine can not start after exhausting the air from the low pressure oil circuit, it is judged that there is air in the high pressure oil circuit, and the air from the high pressure oil circuit is also needed.

Exhaust method: loosen the high-pressure oil pipe of a cylinder and use the starter to drive the diesel engine until the high-pressure oil pipe continues to discharge oil. (do not recommend frequent removal of high pressure oil pipe connections)

 

3) rail pressure can not be established (starter is normal, but unable to start).

 

Check whether there is leakage in high pressure oil circuit.

Check whether the oil circuit is open and check whether the diesel filter is blocked. It is recommended to replace the diesel filter element in time.

Check method: loosen the outlet bolt of the fine filter, use the starter to drive the diesel engine to run, see if there is any diesel injection or outflow, if only a small amount of diesel oil outflow, you can determine the filter plug.

4) rail pressure can not be established (starter is normal, but unable to start).

 

Check whether the initial voltage of the rail pressure sensor is about 0.5V, or whether the rail pressure is set to 350-500bar, if not, first check whether the connector is reliable. If there is no inspection equipment, you can unplug the rail pressure sensor connector and try to start again.

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Check whether the flow metering unit is in good condition, unplug the connector and try to start again.

 

5) loss of crankshaft signal and camshaft signal.

 

Two speed sensors are installed on the diesel engine, respectively, on the outside of the flywheel housing and the high-pressure oil pump. The functions are crankshaft position sensor and cylinder sensor respectively. The timing of the injection of the electronically controlled engine depends on the two sensors. When the diesel engine failed to start, all two signals were lost.

 

6) loss of crankshaft signal and camshaft signal.

 

O two signal loss all possible reasons

 

Sensor damage, wiring harness short circuit or open circuit.

 

2. The sensor is not firmly fixed, resulting in too large or too small clearance between the sensor and the sensing teeth. (usually 1 + 0.5mm).

 

Troubleshooting: check whether the sensor is damaged, whether the wiring harness is connected well, whether the sensor is loose or not.

 

Note: Installation of high-pressure oil pump and flywheel after disassembly and installation should be strictly carried out in accordance with the relevant process documents to ensure signal synchronization.