The sound of a normal diesel engine is regular and uniform. If there is an abnormal noise, it means that the diesel engine has a fault. At this time, the cause of the fault can be determined according to the location, characteristics, and regularity of the sound, so as to improve troubleshooting and reduce hidden dangers. 1. The cylinder head cover emits a slight “click†sound, the cold car is more pronounced than the hot car, and the frequency of the noise changes with the rotation speed. At low speed operation, the metal knock of the cylinder head cover can catch very clear. This is because the valve clearance is too large and the rocker hits the valve stem and makes a sound. At this point, you can check the valve sound gap, if not adjusted. 2. The “click†sound is emitted in the cylinder, which is light at low speed and severe at high speed. This may be due to the fact that the valve touches the top of the piston and is related to the valve clearance. The gap is not normal, should be adjusted in time; if the valve clearance is normal, check the gear mark to see if it is wrong. 3, the upper part of the cylinder emits a crisp metal knocking sound, easy to hear at low speed or sudden speed. This kind of noise is often due to the knocking sound that is generated when the matching gap between the piston pin and the connecting rod bush is too large. 4. When the diesel engine is running, a sound like a pull alarm is issued. This is due to the balance of the bearing out of the pit, caused by the pit. If you make a loud "click" sound, and the sound is connected together, this is due to the balance shaft bearing loose, should replace the bearing. 5, diesel engine gear indoor irregular noise. The higher the rotational speed, the louder the sound, and the louder sounds when starting and stopping. This is due to gear wear, gear bushings and shaft wear, resulting in increased clearance of the gear side, should check the gear and replace it in time. 6, the exhaust pipe has a shot sound, and the exhaust was a circle. This is due to the drop of oil from the nozzle. The nozzle should be removed for grinding or replacement. 7, starting in the lower part of the cylinder heavy and powerful metal knocking sound. It is easy to hear when the speed is low or when the speed increases rapidly. May be the main journal and main bearing wear, caused by excessive clearance. 8. A rhythmic, loud "click" sound is emitted when the engine is working. It may be that the flywheel is loose, causing the flywheel keyway to collide with the crankshaft flat key and causing a crash sound. To tighten the flywheel nut, otherwise, there will be a major accident. 9, the upper part of the cylinder out of a rhythmic "Dangdang" sound, and increase with the increase in speed, the speed down the next step to reduce. This type of knocking is commonly referred to as "knocking", which indicates that the diesel fuel supply time is too early. If a boring knocking sound is generated in the cylinder and the exhaust pipe emits black smoke, the power of the diesel engine is insufficient, and the temperature of the engine body rises, indicating that the fuel supply time is too late and adjusting the fuel supply time can eliminate the above situation.