Question: diesel engine starts, the oil temperature above 30 ℃, the water temperature above 40 ℃, to reach the basic speed, the cylinder has a special ring knock cylinder sound, is not a high-pressure fuel pump valve spring break it? Judgment: 1. Always maintain the diesel engine at the basic speed. 2. With the thumb, index finger and middle finger tip touch high-pressure tubing, compared with other cylinders, pulse weak pulse, and the demarcation point is not clear. 3. Check the cylinder high pressure pump rod ruler line location, if inconsistent with other cylinders, it can make it in the same position. At this moment, there is still a big knocking sound. 4. Quit out of the supply tank after the rejection of cylinder, knock off the cylinder sound, but there is still a slight vibration of high pressure tubing. 5. Throw cylinder, with 27 mm wrench to release the high-pressure pump and high-pressure tubing connector half circle or a circle, the fuel is regularly ejected. According to the above inspection and analysis, you can determine the cylinder valve spring damage, timely replacement, troubleshooting.