1. Burning of cylinder head gasket
After the cylinder head is burned, the diesel engine loses its sealing effect, and blow-by gas, air leakage, oil leakage, and other phenomena occur. The specific performance is as follows:
1) If the two adjacent cylinders are burned, two-cylinder blow-by will occur, the compression pressure of both cylinders is insufficient, and the speed of the diesel engine cannot reach the rated speed.
2) If the burned parts make the cooling water channel communicate with the cylinder, air bubbles will appear in the water tank, white smoke will be emitted from the exhaust pipe, or even drain water. After stopping, the oil level rises due to water leaking into the oil pan.
3) When the burnt parts are at the bolt holes of the cylinder and the cylinder head, and the edges of the cylinder gasket communicate with each other, there is an air leakage sound. Sometimes water and oil leaks, and carbon deposits on the cylinder head bolts and holes.
4) When the burned part makes the cylinder and the lubricating oil hole on the cylinder block communicate with each other, the gas enters the lubrication system, causing the temperature of the engine oil to increase, and the oxidative deterioration is accelerated. It is mainly manifested in the water in the oil pan and the water tank. Motor oil, etc.
1) The plane of the cylinder head and the plane of the machine body are uneven, and the pressure of the cylinder pad is not solid. Such as flat warpage, corrosion pits, each cylinder liner protrudes from the plane of the cylinder block, and the height difference is too large.
2) The cylinder head bolts are loose or the tightening sequence is incorrect, the tightening torque is inconsistent, and the local compression is not solid.
3) The quality of the cylinder gasket is poor, uneven, uneven in thickness, poor in elasticity, or deformed during storage.
4) The engine has been overheated for a long time.
2. Excessive wear on cylinder liner, piston and piston ring
Failure phenomenon: cylinder liner, piston, and piston ring are the main parts of the diesel engine compression system. Due to excessive wear and increased clearance, the sealing performance is deteriorated, air leakage occurs, the compression pressure is insufficient, the startup is difficult, the diesel combustion is incomplete, exhaust Problems such as black smoke and insufficient engine power. The oil will also enter the combustion chamber, the exhaust will emit blue smoke, the oil consumption will increase, and there will be a knocking sound between the piston and the cylinder.
The main reasons:
1) The diesel engine has a long service life (such as about 2000 h). The cylinders, piston rings, and pistons have a large amount of wear, which is normal wear.
2) The wear limit of the diesel engine will not exceed the wear time. The main reason: the material of the parts is unqualified, and the wear resistance of the parts is poor. Incorrect use, such as long-term low-temperature work or cold car after starting to work. Overwork frequently. There is abrasive (dust, dirt, iron filings, etc.) in the intake air and in the engine oil. The connecting rod is deformed, causing it to wear partially. Poor lubrication (such as poor quality and deterioration of lubricating oil).
3. The fuel injection time of the fuel injection pump is incorrect
If the fuel supply time of the fuel injection pump is too early or too late, it is easy to cause difficulties in starting, insufficient power, overheating of the diesel engine, and increased fuel consumption. If the fuel supply time is too early, there will be knocking sound; when the fuel supply time is too late, the smoke color will become white when starting or under a small load, and the smoke color will become black with a medium and large load, and accompanied by a low Percussion. If the fuel supply advance angle between the two cylinders is not the same, it will also cause the problem of unstable speed and knocking sound of the single cylinder.
Reasons for inaccurate fuel supply time:
Mostly the fuel injection pump or timing gear is incorrect. One is the wrong mark, and the other is the inaccurate position of the fuel injection pump. The timing tube method is not used to find the fuel supply time carefully. Due to the wear of the timing gear, it is easy to increase the backlash of the tooth, which will cause the delay of the entire fuel supply time. In addition, it may be because the timing gear mark is wrong, or the key groove of the injection pump shaft is misaligned, but this kind of problem is relatively small. The inadequate fuel supply advancement angle between the two cylinders is mostly caused by the wear of the fuel supply cam of the fuel injection pump and the inconsistent wear of the plunger arm and its fork during long-term use.