The plunger spring of the fuel injection pump will also be worn and deformed by the periodic high-frequency alternating force, thereby shortening its free length and weakening its elastic force. After the elastic force is weakened, the return speed of the plunger slows down. so. When the engine is running at a high speed, the reciprocating motion of the plunger cannot be coordinated with the high-speed rotary motion of the oil pump cam, so that the lift of the plunger is reduced. The fuel supply is reduced accordingly, resulting in a decrease in engine power. Therefore, when the plunger spring is used for 3600-4500h, it should be replaced in time.
The valve spring is affected by high temperature and periodic high-frequency alternating force. After a period of use, wear and plastic deformation will occur, which will weaken the elastic force, resulting in poor valve closing, reduced engine power, black smoke from exhaust, and difficulty in starting. Fault. Therefore, check the spring force of the valve spring regularly. You can put a small piece of iron between the old spring and the new spring, clamp it on a bench vise and compare it to see how shortened it is. When the new spring is compressed to 2/3 of the original length, if the old spring is 2mm shorter than the new spring, it should be replaced. If there are no spare parts for a while, a flat washer of about 2mm can be placed on the old spring to make up for the lack of its elasticity. Under normal circumstances, the valve spring should be replaced after 2500 to 3000 hours of use.
After the spring force of the oil outlet valve is weakened. It will cause serious internal leakage of high-pressure oil, the residual pressure in the high-pressure oil pipe will decrease, and the oil outlet valve will not be seated quickly, so that the oil supply will be reduced and unstable, and the engine will be weak and “travel”. In addition, it will also make the fuel injector weak at the beginning, the fuel cut off is not straightforward, and the phenomenon of back dripping occurs, which leads to deterioration of combustion, overheating of the engine, and black smoke from the exhaust. Therefore, the oil outlet valve spring should be replaced after 3600-4500h of use. If it is bent and deformed, it should be replaced in time.
