Some operators do not understand the structure and working principle of the engine. When repairing tractors and agricultural transport vehicles, they often take it for granted to maintain and repair. The result is self-defeating, resulting in undue failures. Six examples are now listed to draw the attention of the majority of drivers. 1. After the plunger of a small four-wheel tractor equipped with an X195 diesel engine was replaced by a cotton thread at the plunger sleeve locating screw, the engine had a racing fault. The operator thinks that there is a problem with the replaced plunger, and he has changed a new set of plungers, and the result is still a failure. After inspection, the repairman confirmed that there was no abnormality in the governor, but found that the fuel supply time of the fuel injection pump was chaotic. Then the injection pump was dismantled and it was found that a lot of cotton thread was wrapped around the plunger set screw. Originally, in order to prevent oil leakage at the positioning screw of the plunger sleeve, the operator wound a cotton thread on the positioning screw, which may cause the positioning screw not to be inserted into the positioning groove of the plunger sleeve and lose its positioning effect. When the diesel engine is working, the plunger sleeve rotates arbitrarily in the pump casing, and the fuel injection pump is out of control, causing the engine to have a racing fault. 2. Adding iron coils under the cylinder sleeve shoulders causes cracks in the cylinder sleeve. After the cylinder sleeve and piston of the three-wheeled agricultural vehicle equipped with the S195 diesel engine are replaced by the operator, the power of the engine will be reduced significantly after the engine is operated for a short time. The operator also found bubbles in the cooling water. At first, the operator thought that the cylinder mat was damaged, so he replaced a new cylinder head gasket and the fault could still occur. After the dismantling inspection by the repairman, it was found that there was a crack in the circumferential direction at the cylinder sleeve shoulder. Originally, when the operator installed the cylinder liner, in order to prevent the burning of the cylinder head gasket, a fine iron coil was installed under the shoulder of the cylinder sleeve, which caused the cylinder sleeve to protrude too high from the plane of the body. This tightens the cylinder head bolts, the pressure is concentrated in the cylinder sleeve shoulder, resulting in cracks in the cylinder liner. After a new cylinder liner was replaced and the dirt on the contact surface of the cylinder block was scraped off, the fault was eliminated. 3. The installation of a hollow cushion in the vortex room caused a fault. After a tractor equipped with the 195 diesel engine was repaired, the power was reduced, the fuel consumption was increased, the exhaust pipe was severely black smoke, and the exhaust was rich in diesel flavor. The reason is as follows: To improve the compression ratio of the diesel engine, the operator added a hollow washer in the vortex chamber. As a result, the swirling motion of the compressed gas in the combustion chamber was destroyed, which seriously hampered the formation of the combustible mixture, resulting in fuel in the cylinder. Can not completely burn and smoke. For this reason, the fault was immediately removed after removing the gasket. 4. Failure to use a plastic membrane to wrap the hydraulic oil tank cover causing a fault A small four-wheel tractor was in the middle of the operation and suddenly there was a failure that the lifting mechanism could not lift. The reason for this is that in order to prevent dust from entering the hydraulic tank, the operator uses a plastic membrane hydraulic fuel tank cap to tie it firmly. As a result, the ventilation hole on the fuel tank cap is lost. As the oil level in the hydraulic tank drops, the fuel tank Negative pressure occurs inside. When the negative pressure value is greater than the negative pressure value of the hydraulic pump inlet, hydraulic oil cannot be passed through the oil outlet pipe into the hydraulic pump, so that the lifting device cannot lift the agricultural implement. For this purpose, the plastic film on the fuel tank cap was removed and the hydraulic oil was supplied, and the fault was immediately removed. 5. Increased paper cushions between the gear chamber cover and the body cause a malfunction. After a three-wheeled agricultural vehicle equipped with a single-cylinder diesel engine has been repaired, the engine speed fluctuates. After the repairman checked, the reason was found that the operator added a layer of paper pad to the old paper pad to prevent the oil leakage between the gear room cover and the machine body. As a result, the gap between the governor push rod and the short arm of the swing bar was connected. Increasing the speed of the governor reduces the sensitive performance of the governor, which results in unstable engine speed. For this reason, after removing the old paper pad and the added paper pad and replacing it with a standard new paper pad, the fault was immediately eliminated. Incidentally, in order to prevent oil leakage, a thin layer of sealant can be applied to the joint between the body and the gear chamber cover. 6. Inaccurate shaft replacement caused continuous breakage of the axle of the bulldozer. One Dongfang Hongyi 70 bulldozer continuously broke two axles in operation. After inspection, the repairman found that the broken shaft was located on the rear axle of the left-rear truck. According to the machine operator, the rear gantry wheel on the left side of the rear heavy-duty trolley had been lost due to loosening. The repairman's analysis of the broken axle may be due to a problem with the newly replaced teeming wheel. After checking the new roller, it was found that its rim thickness was 6.5 mm thicker than the outer rim. Originally, the roller supported the weight of the tractor. The weight of the rear roller was heavier than that of the front roller. The weight of the inner rear roller was heavier than that of the outer roller. During the operation of the tractor, the front portion of the gantry trolley falls and the rear portion rises. A gap is formed between the rear outside bolster and the chain rail plate, and the load on the rear portion of the gantry trolley presses on the inside wheel. In order to save expenses, the pilots did not replace the supporting wheels in pairs. As a result, the thickness of the rims inside and outside the two wheels was inconsistent. As a result, the new roller was overloaded and the roller broke. After finding the cause of the fault, on the left side of the corresponding coaxial line, remove the old roller and replace it with a new one. After that, the roller axle of the machine will no longer break.