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Trouble Shooting Of Valve Train Of Diesel Generator

Sep. 23, 2021

The abnormal noise of diesel generator valve mechanism includes abnormal valve noise, abnormal valve lifter noise, abnormal noise of synchronous gear, valve and piston collision, etc. The diagnosis and treatment methods are as follows:


(1) Abnormal sound of valve.

1. The valve clearance is adjusted too large.

2. The valve clearance adjustment bolt is loose.

3. The rocker arm of the valve clearance is worn into a groove.

4. The push rod is bent. 

5. The tappet and cam are worn.


Fault diagnosis: When the diesel engine is idling, you can hear the abnormal sound of clicking in the valve chamber, but it does not change with the temperature of the diesel engine, and the abnormal sound when the single cylinder fails to fire does not change. It can be diagnosed as abnormal valve sound .


Problem solving: Remove the valve chamber cover and check the valve clearance. If the valve clearance is too large, the valve clearance is too large. Look at the inspection.


(2) Abnormal sound of valve lifter.

The cause of the failure: The cam surface is worn. When the outer edge is correct, the lifting process and its movement law can be guaranteed. When the cam surface is worn, the continuity of the contact between the valve stem and the cam is broken. When the valve is seated, the valve stem will make a sound when it collides with the cam. The valve mechanism of the diesel engine is a disc cam mechanism. When the camshaft rotates, the cam not only drives the lifter up, but also drives the valve lifter to swing laterally. When the valve lifter and the casing are worn radially and the matching clearance increases, the valve lifter will make a collision sound with the casing when it swings sideways. In addition, the impact of the oil between the valve rocker arm adjusting screw and the upper end of the push rod is difficult to reduce, so noise is generated. Broken springs are also prone to noise.


Diagnosis process: If the valve clearance meets the requirements, the main reason for the noise generated by the valve mechanism is that the cam profile wear does not meet the requirements, the clearance between the valve lifter and the guide tube is too large, there is no oil at the valve rocker adjustment screw, or the valve spring is broken. exclude.


diesel generator

(3) Abnormal noise of the synchronous gear.

1. Most of the engine timing gear is subjected to unstable transmission load, resulting in an impact in the transmission, or the shape of the transmission gear is worn in the transmission, which destroys the correct meshing of the gear, and changes the relative motion form of the contact part of the tooth surface, that is, the sliding friction increases. The rolling friction is reduced. In this way, the wear of the tooth surface is accelerated, slipping and impact are generated, and noise is generated. 2. Failure to replace transmission gears in pairs not only accelerates gear wear, but also causes abnormal seizure. The gear timing is of poor quality and incorrectly engaged, causing noise.


Failure diagnosis: When idling, there is a slight rattle, no rhythm, and obvious at medium speed. At high speed, the sound is messy and there is a broken sound.


When the occlusal gap between teeth is too tight, it will make a clicking sound. The higher the diesel engine speed, the louder the noise.


When the gears bite unevenly, a rattling rhythm will sound. The higher the speed of the diesel generator, the louder the sound. This sound comes from the intermittent sound of the camshaft gear and the intermittent sound of the shaft gear.


The gear shaft made a continuous rattle when it jumped, accompanied by the vibration of the gear chamber cover.


If the abnormal sound is similar to the above phenomenon, it can basically be judged as abnormal sound of the synchronous gear.


Problem solving: If the gears are not replaced in pairs during the repair process, the timing gear will produce abnormal noise, or the quality of the timing gear will be poor, causing the timing gear to make noise. The first two gears should be replaced in pairs, and the latter should be re-selected with good quality gears. If the noise gradually appears due to a long time of use, and from small to large, it indicates that the abnormal noise of the timing gear is caused by excessive wear and should be replaced.


(4) The valve collides with the piston.

The valves of most internal combustion engines are on. When the piston is at the top dead center, the top of the piston keeps a certain distance from the valve. If this distance disappears, the top of the piston will collide with the valve and make a noise. 1. The valve seat ring is too thick. 2. When processing the bottom hole of the valve seat ring, the bottom surface is uneven or the processing depth is insufficient. 3. The valve head is too thick. 4. The valve clearance is too small. 5. The piston model is incorrect. 6. The marking of the spur gear is incorrect.


Fault diagnosis: When the diesel generator is running, you hear the above sound, pinch the nut that fixes the valve cover with your fingers, feel the vibration, and make a preliminary judgment that the valve and the piston collide.


Fault handling: Further identification and handling should be done after disintegration. Do not carry out the failure recurrence test for a long time, so as not to damage the machine or cause a greater failure of the diesel engine.


Jiangsu Starlight Electricity Equipments Co.,Ltd., as an OEM supporting manufacturer authorized by Cummins to provide Chinese diesel generator sets, has professional manufacturing technology, perfect quality management system and strong R&D technical strength. It can provide users with generator sets of various specifications from 15KW to 2500KW. It can also provide users with one-stop service of design, supply, debugging and maintenance at any time. welcome contact us by email sales@dieselgeneratortech.com

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