First, avoid indiscriminate use of butter
Butter is a commonly used grease in maintenance of construction machinery, which can play the role of lubrication and sealing. Therefore, some maintenance personnel will apply butter to the cylinder head gasket when installing the cylinder head gasket, which is believed to improve the sealing performance of the diesel engine. However, this will affect the performance of the diesel engine. If grease is applied to the cylinder head gasket during installation, a gap will be formed between the cylinder head gasket, the cylinder head and the plane of the body. High temperature and high pressure gas can easily impact the cylinder head gasket from there, damage the cylinder head gasket and cause air leakage. In addition, butter placed at high temperature for a long time will also produce carbon deposits, leading to premature aging and deterioration of the cylinder head gasket. Therefore, do not apply butter when installing the cylinder head gasket.
Second, avoid installing new mismatched cylinder liners and pistons.
When replacing the cylinder liner and piston, the new cylinder liner and piston are considered as standard parts and are interchangeable and can be used after installation. In fact, the dimensions of the cylinder liner and piston have a certain tolerance range. When replacing, the size group code of the standard cylinder liner and piston must be checked. The size group code of the standard cylinder liner and piston to be installed must be the same as the size group code of the standard cylinder liner.
3. Avoid not checking the plunger stroke margin
Many maintenance personnel do not pay attention to check the plunger stroke margin. The so-called plunger stroke margin refers to the amount of movement that the plunger can continue to rise after being pushed to the top dead center by the cam on the camshaft. When unscrewing the adjustment bolt or using thicker adjustment pads and washers, the lower position of the plunger moves upwards to reduce the plunger stroke margin. Therefore, when maintaining and commissioning the fuel injection pump, first check the stroke margin to determine whether the fuel injection pump still allows adjustment.
4. Avoid measurement of cylinder clearance
When measuring the cylinder clearance, it cannot be measured in the direction perpendicular to the piston skirt of the piston pin hole, but in other directions. The structural feature of the aluminum alloy piston is a small cone at the top and a big bottom, and the skirt is oval, so the clearance of the cylinder in the circumferential direction is not equal.
When measuring, the gap in the direction of the long axis of the ellipse shall prevail, that is, the gap perpendicular to the direction of the piston pin hole shall be measured for the piston skirt. This measurement is more convenient and accurate, and in the reciprocating motion, the direction of the piston skirt perpendicular to the piston pin hole is greatly worn due to the effect of lateral pressure, so when measuring the cylinder clearance, the piston skirt should be perpendicular to the piston Measure in the direction of the pin hole.
5. Avoid piston flame heating
Because the piston and the piston pin are interference fit, when installing the piston pin, the piston should be heated and expanded first. At this time, some maintenance personnel will directly heat the piston on an open flame. This is very wrong, because the thickness of each part of the piston is not uniform, and the degree of thermal expansion and cold contraction is also different. Open flame heating can cause uneven heating of the piston and easily cause deformation. Carbon dust will also adhere to the piston surface, reducing the life of the piston. If the piston cools naturally after reaching a certain temperature, its metallographic structure will be destroyed, the wear resistance will be greatly reduced, and the service life will be greatly shortened. When installing the piston pin, the piston can be heated evenly in hot oil to slowly expand, and it should not be directly heated by open flame.
6. Avoid sanding bushes with emery cloth
For some inexperienced repairmen, scraping tiles is a difficult job. Because the scraping shoe process is difficult to master, it is not easy for the bearing bush to meet the technical requirements. Therefore, when replacing the bearing bush, some people use abrasive cloth to polish instead of scraping the ceramic tile to increase the contact area between the bearing bush and the crankshaft. This method is very undesirable in actual maintenance, because the abrasive particles on the abrasive cloth are relatively hard, and the bearing alloy is relatively soft, so the abrasive particles are easily embedded in the alloy during the grinding process, thereby accelerating the wear of the journal and Shorten the service life of the crankshaft when the diesel engine is working.
Engine overload, poor heat dissipation or lack of water in the water tank will cause the water tank to boil. If cold water is added immediately, the cylinder head and cylinder block will crack. Therefore, once it is found that the water tank is boiling, emergency measures should be taken to stop the operation so that the cooling water of the diesel engine can be cooled by itself.
Nine, only avoid adding oil
Motor oil is essential in the use of diesel engines and is mainly used for lubrication, cooling and cleaning. Therefore, many drivers will pay attention to check the amount of lubricating oil and add it according to the standard. During the operation of the diesel engine, a large amount of dust will enter the engine oil. If the quality inspection of the lubricating oil and the replacement of the deteriorated oil are ignored, some moving parts of the engine will always work in an environment with poor lubrication, thereby accelerating the wear of various parts.
