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Faults Caused by Low Load Operation of Diesel Generator

Oct. 15, 2019

What are the faults caused by long time low load operation of diesel generator sets? When the load is too low, the exhaust pipe of the generator set will drop oil. If you encounter this problem, do not worry, Jiangsu Starlight Electricity Equipment Co.,Ltd will analyze the cause.

Because there are many places in the diesel engine that adopt the form of pressure seal, such as cylinder liner, piston, and piston ring, and the seal is also adopted between the supercharger and the supercharger rotor shaft. When the load is 1/3 of the engine, it is fully effective, but a slight leakage will occur when the load is too small. Diesel generator should avoid long-term low load operation. Many engine manufacturers have added instructions in user’s manual.

If the diesel generator set is operated under too small load for a long time, the genset faults will occur:

The sealing performance of the piston and the cylinder liner will be worse, the oil will smash into the combustion chamber, the exhaust gas will emit blue smoke, the oil consumption will increase, the economy will decrease, and the combustion chamber carbon deposits will increase, which will aggravate environmental pollution. In the face of exhaust blue smoke phenomenon, users can not be taken lightly, they should timely inspect, repair and remedy of the trouble.

Cummins generator

The oil in the supercharger accumulates to a certain extent and leaks from the joint surface of the supercharger.

Due to the low load, no load and low supercharging pressure of the turbocharged diesel engine, it is easy to cause the sealing effect of the supercharger oil seal (non-contact type) to drop, and the oil enters the plenum chamber and enters the cylinder along with the intake air.

Part of the oil entering to the cylinder is involved in combustion. Part of the oil cannot be completely burned, and carbon deposits are formed at the valve, air intake duct, piston crown, and piston ring, etc, and some are discharged with the exhaust gas. In this way, the oil will gradually accumulate in the exhaust duct of the cylinder liner, and carbon deposit will also form.

Long-term small load operation will lead to the wear of moving parts, and also worsen the sealing performance of the compression system, engine combustion environment deterioration, resulting in the loss of the life of the diesel generator set, and early maintenance period of the generator.

Therefore, it is emphasized that the low load / no load operation time should be minimized no matter it is naturally aspirated or turbocharged engines, and the minimum load should not be lower than 25%-30% of the rated power of the unit.

In summary, the long-term operation of the diesel generator set under low load will cause serious machine wear, serious aging of the seal, and shorten the life of the generating set. So it is very important and necessary to do daily maintenance to your equipment.

Basic Maintenance for A Diesel Generator

First-class technical maintenance: the accumulated working load of diesel generators is 250 hours or 6 months, and other applications are 500 hours or one year, and maintenance work is required;

1) Clean dust and oil contamination on all parts of the machine, and check for leaks at the joints of each part and dispose of them in time.

2) For electric start unit, should check the terminal voltage, specific gravity and liquid level of the battery.

3) Check the cooling system for oil and water seepage and sufficient coolant.

4) Check the oil level in the crankcase. When it is insufficient, add the oil to the standard scale. If it is found that the oil level suddenly rises, it should be checked to see if there is any water leakage into the bottom of the tank, and the leak should be removed in time.

5) Check the fuel capacity in the fuel tank. If it is insufficient, it should be filled in time.

Starlight Power recommends 300KW 375KVA Cummins Diesel Generator - New Genset

Cummins generator

Engine Data




CCEC Cummins

Prime power


Standby power




Bore and Stroke

140 x 152 mm




Turbocharged and Intercooled

Rated Speed



ISO 3046

Compression Ratio

14.0 : 1

Fuel Consumption (100%)

71.9 L/h


54.9 L/h


38.9 L/h


21.8 L/h


9.8 L/h

Alternator Data





Rated Power




Number of Phase


Insulation Class


Protection Grade


Voltage Regulation

AVR automatic voltage regulation

Excitation Mode

Brushless self-excited

Controller Data


Deep Sea




LCD display


Chinese / English / Spanish / Russian/...


AMF automatic operation


Automatic start and auto mains failure control module

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