1. The car has high pressure fire, but the starting time is long, and the car can finally run;

 

2. During the starting process, the crankshaft will be reversed, and the intake manifold will be backfired;

 

3. The idling speed of the car is unstable and the vibration is serious, which is similar to the failure of the car lacking cylinder;

 

4. The acceleration of the car is insufficient, the car cannot run, and the speed exceeds 2500 rpm;

 

5. The vehicle has high fuel consumption, the exhaust emission exceeds the standard, and the exhaust pipe will produce black smoke.

 

Common failures of camshafts include abnormal wear, abnormal noise, and fracture. Abnormal wear and tear symptoms often appear before abnormal noise and fracture occur.

1. The camshaft is almost at the end of the engine lubrication system, so the lubrication condition is not optimistic. If the oil supply pressure of the oil pump is insufficient due to the long-term use, or the lubricating oil passage is blocked so that the lubricating oil cannot reach the camshaft, or the tightening torque of the bearing cap fastening bolts is too large, the lubricating oil cannot enter the camshaft clearance, and the Causes abnormal wear of the camshaft.

 

2. The abnormal wear of the camshaft will cause the gap between the camshaft and the bearing seat to increase, and the axial displacement will occur when the camshaft moves, resulting in abnormal noise. Abnormal wear will also cause the gap between the drive cam and the hydraulic lifter to increase, and the cam will collide with the hydraulic lifter when combined, resulting in abnormal noise.

 

3. Serious failures such as breakage of the camshaft sometimes occur. Common causes include cracked hydraulic tappets or severe wear, severe poor lubrication, poor camshaft quality, and cracked camshaft timing gears.

 

4. In some cases, the failure of the camshaft is caused by human reasons, especially when the engine is repaired, the camshaft is not properly disassembled and assembled. For example, when removing the camshaft bearing cover, use a hammer to knock it down or pry it with a screwdriver, or install the bearing cover in the wrong position, causing the bearing cover to not match the bearing seat, or the tightening torque of the bearing cover fastening bolts is too large. When installing the bearing cover, pay attention to the direction arrows and position numbers on the surface of the bearing cover, and use the torque wrench to tighten the bearing cover fastening bolts in strict accordance with the specified torque.