Fault performance:
After the second level maintenance, the engine of Caterpillar excavator is put into test run. There is a "pop, pop" sound from one section of the intake pipe of the engine. If you cover the intake pipe mouth with your hand, the sound seems to be reduced. When idling, the sound is very clear and obvious, similar to the sound when the cylinder gasket is damaged.
Fault analysis:
It is found that there is no valve clearance at the intake valve of cylinder 1 of the engine However, the valve clearance of the intake valve of this cylinder has been adjusted before the test run. Why is there no valve clearance all of a sudden? In addition, the valve spring is in a compressed state. When the rocker arm shaft assembly is disassembled, the valve spring will automatically return. This indicates that it is not the insufficient tension of the valve spring, but the poor performance of other components
Remove the valve rocker arm assembly. There is no jamming on the valve rocker arm, and the valve push rod is bent and deformed. Re calibrate the valve push rod, install the valve rocker arm shaft assembly, adjust the valve clearance, and re test the engine. The intake pipe of the diesel engine still makes a "pop, pop" sound
Re check the valve and find that the valve is in the open position again. The valve spring is compressed and the valve push rod is slightly bent and deformed.
After removing the cylinder head, it was found that there was diesel in the cylinder of cylinder 1. When turning the crankshaft, it was found that the valve tappet of the intake valve of cylinder 1 did not move Neither up nor down, stuck in the guide hole of the valve lifter, causing the intake valve to be in the normally open state, causing the intake pipe to make a "pop, pop" sound
After investigating the cause, it was learned that the valve tappet was worn and hairy during the maintenance of the engine. When it was installed into the tappet guide hole, it was forcibly pressed by a screw driver and other tools to contact the cam and sit down In this way, when the camshaft rotates, the cam pushes the tappet into the tappet guide hole, and the tappet and the tappet hole are too tight to return to the seat (the tension of the valve spring cannot make it return). As a result, the intake valve of this cylinder is normally open when the diesel engine operates. In this case, the first cylinder will not work normally When the intake valve of this cylinder takes in air on the one hand and the engine compresses the exhaust stroke for work; When exhaust gas or gas in the cylinder is discharged from the exhaust pipe, it is also discharged from the intake valve in large quantities. Therefore, the intake pipe of the diesel engine section emits a "pop, pop" sound
Replace the valve lifter with a new one, reinstall it correctly and try again. The fault phenomenon disappears
