3. Reasons for insufficient compression force:
(1) Leakage of intake and exhaust valves. There are two reasons for this type of air leakage: First, the valve clearance is too small, which makes the valve not tightly closed, and the valve clearance needs to be readjusted. The other is that there may be spots on the valve sealing cone, such as rust, carbon deposits and other debris, which also makes the valve not tightly closed. The crankshaft can be swayed during inspection. If you hear "squeak, squeak" sounds in the air cleaner and exhaust pipe, it means that the intake and exhaust valves are leaking. Need to grind the valve.
(2) The cylinder head nut is not tightened or the cylinder gasket is damaged. When rotating the crankshaft, if there is a sound of air leakage at the joint surface of the cylinder head and the body, the cylinder head nut may not be tightened, or the cylinder head gasket may be damaged. If it is the former, tighten it as required. If it is the latter, when the cylinder head gasket is not seriously damaged, use asbestos thread to repair the damaged area, and replace it with a new gasket when it is severe.
(3) Excessive wear of the piston ring. When rotating the crankshaft, there is a sound of air leakage inside the body (such as the oil lower shell), which is mostly caused by the piston ring. Some clean oil can be added to the cylinder. If the compression force is obviously increased after adding, the piston ring should be replaced at this time.
(4) The piston ring openings are moved to a straight line (commonly known as the counterpart), or the piston ring is stuck in the ring groove due to carbon deposits, and the compression cylinder cannot be ejected. The phenomenon is that when the crankshaft is rotated, there is a sound of air leakage in the crankcase. The piston ring should be removed to remove carbon deposits. If the ring mouth is moved to a straight line, the positions of the openings should be evenly distributed, but the direction of the piston pin must be avoided.
(5) The fuel injector fixing bolt is loose. The fuel injector on the cylinder head is leaking air and should be tightened.
4. Other reasons:
For example, the bearing bush or copper sleeve is seized, making the crankshaft unable to rotate; the piston is installed reversely or the air filter is blocked, etc., which also make the diesel engine unable to start. Although such cases are relatively rare, they are also worthy of attention.
