What causes abnormal sounds in a generator?

Abnormal sound in generators can be caused by several factors, including mechanical knocking, wear and tear of the moving parts, improper installation or adjustment, and faulty internal interface rubber rings between the diesel engine and generator. 

Mechanical knocking is usually heard when the clearance between the piston pin and connecting rod small head bushing is too large, or the piston pin and pin seat are too loose, leading to an impact effect that generates a loud noise. Wear and tear of the moving parts can also cause abnormal sounds, such as rattling or grinding noises. 

Improper installation or adjustment can lead to vibrations, further increasing noise levels. Faulty internal interface rubber rings between the diesel engine and generator can also cause abnormal sounds. Additionally, worn-out gears or bearings can make a generator run noisier than usual.

Troubleshooting generator noise

Troubleshooting a generator's abnormal sound can involve checking the fuel level, ensuring that the switch is firmly in the “on” position, and looking for any liquid leaks like oil or fuel. If there are no issues with these components, then it may be necessary to replace them. Other causes of abnormal noise include valve clearance problems, internal bearing failure, and worn-out parts.

Generator Noise Diagnosis

Diagnosis of abnormal generator sound can be made by determining where the sound comes from, such as inside the valve chamber, body, front cover, or junction between the generator and diesel engine. 

Common causes of abnormal noise include poor fuel quality or fuel system failure, improper valve clearance adjustment, broken valve springs, and worn-out bearings or individual components. 

To diagnose; these issues, it is recommended to shut down the generator quickly after cooling down and inspect for any signs of wear and tear. If necessary, replace parts with new ones or adjust settings accordingly. 

Valve Clearance Specifications

The valve clearance specifications for diesel engine generators vary depending on the model and manufacturer. Generally, it is recommended to check and adjust the valve clearance after 1 year or 300 hours of use. 

For example, Briggs & Stratton engines require an intake valve clearance of 0.10 0.15 mm, Honda engines require an exhaust valve clearance of 0.15 + or - 0.02 mm, and Vanguard 18hp engines require an exhaust valve clearance of 0.004 - 0.006 in. Additionally, some models may require additional maintenance, such as oil changes or spark plug replacements.

Valve Clearance Adjustment Tools

Valve clearance adjustment tools for diesel engine generators include a feeler gauge, an adjustable wrench or screwdriver, and a lockout. The feeler gauge should be used to measure the resistance between the valve stem and the rocker lever, while the adjustable wrench can be used to adjust the clearance of each valve. It is recommended that valve clearance adjustments are made with assistance from authorized distributors. 

 

How To Adjust Valve Clearance

A diesel engine generator's valve clearance can be adjusted by loosening the lock nut and turning the valve adjustment screw with a feeler gauge until there is only a little resistance. The gap should be 0.15–0.2 millimeters.

Holding the knockout steady with a wrench or screwdriver/Allen wrench, adjust the valve clearance with these tools before tightening the lockout and measuring again. If necessary, mark a sign on the damper and rotate the crankshaft for 360° before making any adjustments. Finally, check how your engine responds to this adjustment to determine whether it is wide or narrow than what was specified in your manufacturer's manual.

Valve Clearance Adjustment Intervals

Valve clearance adjustment intervals for diesel engine generators vary depending on the type of engine and its operating conditions. 

Generally, valve clearance should be adjusted when the lash clearance is too tight, as this can cause exhaust gases to leak past the valve. On air-cooled OHV engines, proper valve adjustment is an important maintenance requirement that must be done according to manufacturer specifications. 

For four-cylinder engines, one should use a 1-2-inch drive and engine bearing tool to rotate the engine clockwise until cylinder number 4 appears. If the clearance between the valve stem and rocker is not within the engine manufacturer's tolerance, it will either open too wide or close too narrowly, leading to poor performance.