1. When the diesel engine has a heavy and continuous knocking sound at the lower part of the crankcase, the sound is clear and recognizable at low speed and more obvious at heavy load. The same opportunity oil pressure decreases with the decrease, which is caused by the excessive clearance of the main bearing bush of the crankshaft.

2、当发起机低速忽然改动转速时，在气缸上部发出“铛、铛”的响声，这是活塞销与连杆衬套、或与活塞销座的配合间隙过大所致。

2. When the engine suddenly changes the speed at low speed, the sound of "bell, bell" will be sent out at the upper part of the cylinder, which is caused by the excessive fit clearance between the piston pin and the connecting rod bushing or with the piston pin seat.

3、当发起机高速运转时，发出“咯噔、咯噔”闷击声，忽然减小油门时尤为严重，这是因主轴瓦轴向间隙过大所致

3. When the engine runs at high speed, it makes a "cluck, cluck" dull sound, especially when the accelerator is suddenly reduced, which is caused by the excessive axial clearance of the main shaft pad

4、当在气缸全长部位听到轰鸣、沉闷的“空咚、空咚”的敲击声，且翻开加机油口盖时发现有气泡（阐明有漏气现象），这是活塞与缸套配合间隙过大所致。

4. When a loud and dull knocking sound of "empty Dong, empty Dong" is heard at the full length of the cylinder, and bubbles are found when opening the oil filler cover (indicating that there is air leakage), which is caused by the excessive matching clearance between the piston and the cylinder liner.

5、若在同一部位略靠曲轴方向听到“嘎、嘎、嘎”的撞击声，则是连杆扭曲致使其在工作中摇晃的敲击声，后两种声响在改动转速时更能明显听到，且较易于区别；沿气缸上、下各处均有相似小铁锤轻击铁块的声音，柴油机排气管冒蓝烟（伴有烧机油现象），用长柄螺丝刀抵在缸体处更易于听出，即可判定是活塞环侧隙过大或环折断所致。

5. If the impact sound of "GA, GA, GA" is heard in the same part slightly close to the crankshaft direction, it is the knocking sound of the connecting rod shaking due to the distortion of the connecting rod. The latter two sounds can be heard more obviously when changing the speed and are easier to distinguish; There is a similar sound of small hammer tapping the iron block all over the upper and lower parts of the cylinder, and the exhaust pipe of the diesel engine emits blue smoke (accompanied by oil burning). It is easier to hear when touching the cylinder block with a long handle screwdriver. It can be determined that it is caused by excessive side clearance of the piston ring or broken ring.

6、当柴油机忽然改动负荷时，在曲轴箱左近（气缸体中部至下部范围内）可明显地听到急促的“空、空、空”钝哑的敲击声，并随负荷或转速的增加而急剧变化，响声增大，翻开加机油口盖可听得更分明，无负荷时则不明显。这是由于连杆瓦过度磨损而形成连杆瓦与曲轴连杆轴颈配合间隙过大所致。

6. When the load of the diesel engine changes suddenly, the blunt and dumb knocking sound of "empty, empty and empty" can be obviously heard near the left of the crankcase (within the range from the middle to the lower part of the cylinder block), and changes sharply with the increase of load or speed. The sound increases. It can be heard more clearly by opening the oil filler cover, but it is not obvious when there is no load. This is due to excessive wear of the connecting rod bush, resulting in excessive fit clearance between the connecting rod bush and the crankshaft connecting rod journal.

7、若使柴油机某缸断油，假如此异响立刻消逝，则阐明是该缸的连杆瓦响。

7. If the oil of a cylinder of the diesel engine is cut off, if the abnormal noise disappears immediately, it indicates that it is the connecting rod bush noise of the cylinder.