Compared with the gasoline engine, diesel engine abnormal sound diagnosis is more difficult to grasp, this is decided by the structure characteristics and working characteristics of the diesel engine, such as compression ratio, thermal load, work is relatively rough, big noise, broken oil cannot instantly, and even some diesel oil at the opening of the position of the people not easy to close, to the diagnosis of abnormal noise also brings inconvenience. However, the abnormal sound of the diesel engine has its specific rules, as long as the analysis and comparison, look at the phenomenon of grasping the essence, it is possible to find out its regularity.
Engine knock
Baotou North heavy truck parts of the engine ignition is due to the ignition delay is too long, the pressure rise rate is too large, resulting in rough engine and the formation of. It is characterized by a sharp, crisp, continuous, metallic percussion sound during rapid acceleration. It is more obvious in idle speed or small load, accompanied by vibration. At high load and high speed, the noise is relatively weak, the operation is relatively stable.
The reason
The fuel injection advance angle is too large.
The label of diesel oil does not meet the standard, and the value of sixteen is too low.
The fuel injection quantity is too large or the oil delivery interval is not uniform.
The atomization quality is too bad for the injector of North Baotou heavy truck.
Engine temperature is too low.
The diagnosis and treatment methods
Firstly, the method of vehicle road test was used. To high-grade low-speed driving, then throttle rapidly plus in the end, if the engine emits strong and sharp percussion sound, and the long time does not disappear, and slightly lift the accelerator pedal, the sound immediately weakened or disappeared, and the emergence of sound with the throttle, it can be considered as fire percussion sound. Injection time can be slightly delayed, and then road test. If the sound disappears, it means that the fuel injection time is premature.
If the fuel injection time is delayed, the sound does not change, indicating that the oil supply is accurate, the diesel oil can be replaced and the road test is carried out. If the noise disappears, the diesel oil quality is poor.
The use of half off oil test, that is, to loosen the high-pressure oil pipe connector, so that part of the oil sprayed on the outside, in order to reduce the amount of oil into the cylinder. If the sound and smoke disappear, it is explained that the cylinder oil supply is too large.
If the half break oil test is used, the sound only weakens and does not disappear, and the sound of the oil must be completely cut off, and then the sound of the knock of the oil cylinder is caused by the premature delivery time of the oil cylinder or the atomization quality of the injector. Attention should be paid to check the injector spray.
Because of the individual cylinder oil volume knocking caused by the fire, can be taken after a cold start, judging method for the exhaust manifold corresponding to the touch cylinder; for large load is knocking, touch the cylinder injector and near the lower cover, such as the feeling of being touched and cylinder temperature than the other cylinder heat, then is the cylinder oil supply amount is too large. Can also be used to hold a high-pressure oil pipe, the larger the feeling of pulsation is the cylinder oil supply is too large.
The individual cylinder fuel supply is too large or the delivery period should be removed early, Baotou beiben heavy truck parts injection pump debugging of the cylinder oil and oil separation in the test angle, and inspect the other cylinder oil and oil angle.