A truck emitted blue smoke from the engine exhaust pipe during use and lacked power. After replacing the piston rings many times, the problem remained the same.

1. Troubleshooting and troubleshooting

Based on the above phenomenon, this failure is obviously caused by the poor sealing of the piston ring. This conclusion was also confirmed when the piston ring was inspected. However, the fault still cannot be eliminated after replacing the piston rings many times, so there must be another reason. So I opened the cylinder head and took off the oil pan. When I checked the crankshaft, I found that its axial movement was nearly 3mm (standard is 0.08~0.20mm). When replacing the piston ring, replace the crankshaft thrust washer so that the axial clearance returns to normal and the fault no longer occurs.

2. Analysis of fault results

Generally speaking, replacing the piston rings can improve the sealing of the cylinder, thus solving the problems of oil burning and insufficient power. It is feared that due to the excessive axial clearance of the crankshaft in the engine of this vehicle, severe axial movement destroyed the verticality of the piston operation, which in turn aggravated the wear of the piston ring and the cylinder wall, causing the piston ring and the cylinder to be damaged in a short period of time. If the gap between them is too large, the problem of insufficient power to burn engine oil cannot be fundamentally solved.