Diesel generator sets are core power supply equipment widely used in industrial production, emergency backup and other fields. During long-term operation, due to factors such as component wear, improper maintenance, and abnormal operation, various faults may occur, which will affect the stable operation of the unit. The following are 10 common faults of diesel generator sets, including their fault manifestations, cause analysis and corresponding troubleshooting measures, with a focus on the professional operation specifications of Cummins diesel generator sets.
I. Wear of Transmission Gears with Excessive Clearance
Fault Manifestation: Abnormal noise is emitted at the front cover plate, and an impact sound can be heard when the Cummins diesel generator set suddenly decelerates. This noise is usually caused by the collision between the worn gears due to excessive clearance, which affects the stable transmission of power.
Troubleshooting Measures: First, check and adjust the gear clearance to ensure it is within the specified range. Then, carefully inspect the wear condition of the gears; if the tooth surface is severely worn, pitted or cracked, the gears should be replaced in time to avoid further damage to the transmission system.
II. Excessive Clearance of Intake and Exhaust Valves
Fault Manifestation: A rhythmic and relatively loud noise can be heard at the cylinder head when the diesel generator is running. Excessive valve clearance will lead to delayed opening and early closing of the valves, affecting the air intake and exhaust efficiency of the engine, and even causing incomplete combustion of fuel.
Troubleshooting Measures: The valve clearance should be recalibrated strictly in accordance with the technical parameters of the diesel generator set. Before calibration, ensure that the engine is in a cold state, and use a feeler gauge to detect and adjust the clearance of each intake and exhaust valve to meet the manufacturer's specified standards.
III. Valve Colliding with Piston
Fault Manifestation: A heavy, uniform and rhythmic knocking sound is emitted at the cylinder head during operation. When gently holding the nut of the cylinder head cover with fingers, a collision feeling can be clearly felt. This fault is very dangerous and may cause serious damage to the valve, piston, cylinder head and other key components if not handled in time.
Troubleshooting Measures: First, remove the cylinder head cover to check the cause of the collision. Generally, it is caused by incorrect valve clearance or wrong piston model. Adjust the valve clearance to the specified value first; if the collision still exists, check whether the piston model is correct. If collision occurs, the valve pit can be properly deepened, or a piece of red copper gasket with a thickness of 0.2mm or 0.40mm (the shape is the same as the bottom surface of the cylinder) can be added to increase the distance between the valve and the piston and avoid collision.
IV. No Engine Oil Between the Rocker Adjusting Screw and the Spherical Seat of the Push Rod (Causing Abnormal Noise During Operation)
Fault Analysis: A "squeaking" sound caused by dry friction can be heard at the cylinder head. This is because the lack of engine oil between the rocker adjusting screw and the spherical seat of the push rod leads to direct friction between metal parts, which not only produces noise but also accelerates the wear of the parts.
Troubleshooting Measures: Remove the cylinder head cover immediately, check the lubrication condition of the relevant parts, and add engine oil that meets the specifications to ensure that the friction surface is fully lubricated. After adding oil, start the generator set to run idly for a period of time to confirm that the abnormal noise disappears.
V. Excessively Small Radial Clearance of Crankshaft Rolling Bearings
Fault Manifestation: A particularly sharp noise is emitted when the diesel generator is running, and the noise becomes clearer when the throttle is increased. Excessively small radial clearance will cause the bearing to be in a state of excessive compression, increasing the friction resistance during operation, and even leading to bearing overheating and damage.
Supplementary Note: If the radial clearance of the crankshaft rolling main bearing is excessively large, a "rumbling" sound will be emitted during operation. In this case, the rolling bearing with abnormal noise should be inspected in detail, and replaced in time if necessary to ensure the stable operation of the crankshaft.
VI. Broken Valve Spring, Bent Tappet, or Damaged Push Rod Bushing of the Diesel Generator
Fault Manifestation: A rhythmic slight knocking sound is emitted at the cylinder head. The broken valve spring will cause the valve to fail to close tightly, resulting in air leakage; the bent tappet and damaged push rod bushing will affect the normal movement of the valve mechanism, leading to abnormal valve opening and closing.
Troubleshooting Measures: Stop the generator set immediately, disassemble and inspect the relevant components of the cylinder head, replace the damaged valve spring, bent tappet and damaged push rod bushing, and recalibrate the valve clearance after replacement to ensure the normal operation of the valve mechanism.
VII. Excessively Large Clearance Between Piston and Cylinder Liner
Fault Manifestation: A knocking sound is heard on the outer wall of the cylinder when the diesel generator is running, and the knocking sound intensifies as the speed increases. Excessively large clearance between the piston and the cylinder liner will lead to insufficient compression pressure of the cylinder, reduced engine power, increased fuel consumption, and even oil burning and smoke emission.
Troubleshooting Measures: Check the wear condition of the piston and cylinder liner. If the piston is worn beyond the limit, replace the piston; if the cylinder liner is seriously worn, scored or out of round, replace the cylinder liner according to the wear condition to ensure that the clearance between the piston and the cylinder liner is within the specified range.
VIII. Wear of Front and Rear Thrust Bearings of the Main Shaft, Leading to Front and Rear Movement of the Main Shaft Due to Excessive Axial Clearance
Fault Manifestation: A collision sound caused by the front and rear movement of the crankshaft is heard when the diesel generator is running. Excessive axial clearance of the main shaft will affect the positioning accuracy of the crankshaft, leading to unstable operation of the engine and even damage to the thrust bearing and other components.
Troubleshooting Measures: Check the axial clearance of the main shaft and the wear degree of the thrust bearing. If the axial clearance exceeds the specified value or the thrust bearing is severely worn, replace the thrust bearing in time and adjust the axial clearance to ensure that the main shaft runs stably without obvious front and rear movement.
IX. Too Loose Fit Between Piston Pin and Bushing Hole of Connecting Rod Small End
Fault Manifestation: A light and sharp sound is emitted when the diesel generator is running, and this sound is particularly clear during constant speed operation. Too loose fit will cause the piston pin to shake in the bushing hole of the connecting rod small end, producing impact noise and accelerating the wear of the piston pin and bushing.
Troubleshooting Measures: Replace the bushing of the connecting rod small end, and ensure that the fit clearance between the piston pin and the bushing hole is within the specified range after replacement. This can effectively eliminate the abnormal noise and avoid further damage to the connecting rod and piston components.
X. Too Early or Too Late Fuel Injection Time of the Diesel Generator
Fault Manifestation: A rhythmic crisp metal knocking sound or a low and unclear knocking sound is emitted in the cylinder. Too early fuel injection will cause the fuel to ignite in advance when the piston is still moving upward, resulting in knocking; too late fuel injection will lead to incomplete combustion of fuel, reduced engine power, and increased exhaust temperature.
Troubleshooting Measures: Adjust the fuel injection advance angle strictly in accordance with the technical requirements of the diesel generator set. The adjustment method should be based on the model of the generator set, and professional tools should be used to ensure the accuracy of the fuel injection advance angle, so as to restore the normal combustion state of the engine.
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