Three types of faults that cause diesel engines to fail to start

 

1. The starter cannot drive the diesel engine to run

 

Performance: Turn on the starter switch, the starter does not rotate or idling.

 

Causes: Starter system failure; internal engine stalling; clutch or transmission stalling; starter gear and flywheel gear ring stalling.

 

2.The starter can drive the diesel engine to run, but no start signs

 

Performance 1: Loosen the bleed screw plug of the fuel injection pump and pump oil with a hand oil pump. No oil can be discharged from the bleed screw plug or only foamy diesel is left for a long time.

 

Reason: Generally, this phenomenon can be judged as a low-pressure oil circuit failure. Possible reasons: no oil in the fuel tank, unopened fuel tank switch or clogged fuel tank cap vent; the fuel pipe (suction pipe) is clogged or leaking; the filter element is clogged; The filter screen of the oil pump is blocked; the oil pump works poorly; the pressure reducing valve fails, which reduces the oil pressure in the low-pressure oil chamber; the oil circuit freezes and blocks in winter; the wrong diesel brand is used in winter, and paraffin is precipitated after condensation, causing the oil circuit to block.

 

Cause: This situation can generally be determined to be a high pressure oil circuit failure. ①Injection pump failure. Coupling active disk and passive disk connection key damage; tappet and plunger foot clearance clearance is too large; rack stall or other reasons to stop the plunger in the non-oil supply position; oil valve is not sealed, stuck or spring is broken; ; The failure of the pressure limiting valve causes insufficient oil pressure in the low pressure chamber. ②The injector is malfunctioning. The fuel injection hole is blocked, the needle valve cannot be opened due to carbon deposition or sintering; the fuel injection pressure is adjusted too high. ③There is air in the high-pressure oil circuit; the high-pressure oil pipe is broken or the joint is loose.

 

3. The starter can drive the diesel engine running, exhaust smoke, but can not drive the vehicle idling in place

 

Performance 1: The exhaust pipe cannot exhaust black smoke and the vehicle cannot be started.

 

Causes: Intake blockage; serious mis-timing of injection timing; insufficient injection pressure, poor atomization, low cylinder pressure, poor quality diesel fuel, etc.

 

If such a situation occurs, there are several diagnostic treatment methods to choose from: ① check whether the intake and exhaust pipes are clear, whether the air filter is blocked, whether the exhaust brake valve is completely open, etc.; ② check whether the oil supply advance angle is in line with the regulations; ③ check the technical condition of the injector; ④ if the oil supply system works normally, the cylinder pressure should be checked. If the pressure is not enough, check the valve, piston ring, cylinder gasket, cylinder liner, etc.

 

Performance 2: The exhaust pipe exhausts white smoke, and the vehicle cannot be started.

 

Reasons: there is water in the diesel; the engine temperature is too low (the low-temperature start-up preheating device fails); the fuel injection timing is not accurate (usually too late); the gas or fuel supply is insufficient; the fuel injection quality of the fuel injector is poor; the cylinder pressure insufficient.

 

The following diagnosis and treatment methods can be used for this kind of fault: ① Approach the outlet of the exhaust pipe muffler with your hand. If water drops on your hand after the white smoke passes, it means that water has entered the combustion chamber. Check the quality of the diesel oil and the oil level of the oil pan. If the oil level rises, find out the leaking part; ②If the fuel supply is good but the vehicle cannot be started, check whether the preheating device is good and whether the fuel supply timing is accurate, and adjust if it is not suitable;③If the above items are normal, check whether the valve foot clearance, fuel injection quality, and cylinder pressure are appropriate.