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Insufficient Power of Diesel Generator Set

Sep. 08, 2018

Why is the power shortage of diesel engine in generator set? The power of diesel engine is affected by many factors like other internal combustion engines.

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1. Look at the coke deposit and check the working conditions.


The coke deposit at the exhaust port of the diesel engine is black and gray, and the surface is covered with a layer of white frost, and the carbon deposit layer is extremely thin, which indicates that the diesel engine is working well. Carbon black color and not wet, indicating that the diesel engine oil slightly. The coking of the exhaust port in a certain cylinder is thicker, indicating that the injector of the cylinder is not working well or the seal of the cylinder is becoming worse, and should be repaired or replaced. Individual vent wetting or oil flow marks, indicating that the cylinder burning oil, should be repaired. The coking layer of each cylinder vent is thicker and darker, which is mainly caused by the low working temperature or the late injection, and the serious phenomenon of post-combustion.



2. Check the smoke and wear.


In the diesel engine work, open the oil cap, if there is a thick smoke from the oil cap, called low smoke. In the diesel engine work, open the oil cap, if there is a low smoke from the oil cap, called smoke. The smoke phenomenon is serious, indicating that piston, cylinder sleeve, piston ring and other parts wear seriously. Open valve chamber cover, if a trace of blue or white smoke from the valve root (valve face), called smoke. The serious smoke phenomenon indicates that the valve and valve seat are worn seriously or ablated, or the valve clearance is too small or no gap.


3. Check water temperature and cooling


If the cooling system water temperature of diesel engine is too high (over 100 ℃), it can be concluded that the cooling water cavity scale is too thick or the cooling system components (thermostat, pump, fan, etc.) are inefficient or ineffective.


4. Check the gas distribution and phase.


After a long period of work, the timing gear, cam surface, follower column and tappet will wear and tear, so that the opening and closing time of the intake and exhaust valve will be delayed backward and deviate from the optimum valve phase, thus reducing the charging efficiency and reducing the power of the diesel engine. Therefore, to check the diesel engine valve phase regularly, if not in line with the requirements should be adjusted in time.


5. Check the pressure and leak.


Pressure gauges can be used to measure cylinder pressure and find out cylinders with poor sealing. 


The reasons for the poor seal of the cylinder are as follows: Valve clearance or clearance is too small, piston and cylinder sleeve and piston ring end surface clearance is too large, ring groove carbon, etc. In the operation of diesel engine, if "hoarseness" can be heard when the air filter is close to the air filter, the leakage is related to the valve. At this point, combined with the smoke situation can confirm the cause of the fault.


6. Check the exhaust and smoke.


Diesel engine normal operation, generally not smoke or some light gray smoke, sometimes with the naked eye difficult to see. If black smoke, then the cylinder oil less gas, combustion is incomplete. If blue smoke is emitted, the wear gap between cylinder sleeve and piston, valve and valve duct is too large; if white smoke is emitted, fuel oil is mixed with water, or diesel oil is not completely burned, and after vaporization, it comes out from the exhaust pipe.



7. Check fuel injection and chaka lag.


The injection pump should not be biased, not dripping oil, good atomization, appropriate range, can be heard when the injection of the "punching, fighting" sound, with the hand touch high pressure tubing pulse dynamic. Good fuel injection does not completely mean that the fuel system is free from problems. Therefore, it is also necessary to check whether the throttle rod and joint are sticking or loosening.


8. Check injection timing


Check timing is to check the timing of injection, that is, whether the fuel supply advance angle conforms to the regulations. The fuel supply is too late, the diesel engine is difficult to start, the combustion is not complete, the exhaust smoke, the engine temperature is too high, the power is insufficient. If the fuel supply is too early, the diesel engine will have percussive sound while working, and the parts will easily be damaged, and the engine power will also be affected.


9. Check Phenomenon, and circuit


For electrically controlled diesel engines, the following two conditions will also lead to insufficient power. 


Thermal protection state: If the temperature of the electronically controlled diesel engine is abnormal, it may be that the coolant temperature is too high. The intake temperature is high and the fuel temperature is too high, it is caused by cooling fluid temperature sensor circuit failure (e.g. open circuit); intake temperature sensor circuit fault (such as open circuit).


Failure protection mode: If the electronic control components of the electronically controlled diesel engine fail, it may be the damage of the rail pressure sensor or the fault of the line, the driving fault of the fuel metering valve, the damage of the valve or the malfunction of the line, etc.


Once the diesel generator set breaks down in the process of operation, it is easy to cause the power shortage of the genset. It can be found on the ammeter or on the control panel of the generator set. What are the reasons for the insufficient power of the diesel generator set?



1. The diesel generator set is overheated and the ambient temperature is too high.


The oil and cooling water temperature is very high, the exhaust temperature also greatly increases. 


Exclusion methods: Overhaul coolers and radiators to remove scale; check if the pipe is too small. If ambient temperature is too high, ventilation should be improved and cooling measures should be strengthened temporarily.


2. Fuel system failure


After the throttle is added, the power or speed is still not high.


1) Fuel filter entering air or blocking

Exclusion methods: Remove fuel system air or replace fuel filter core.


2) Insufficient fuel supply for fuel injection pump

Exclusion methods: To inspect the repair or replacement of a pair.


3) Poor atomization of injectors or low injection pressure

Exclusion methods: Spray observation or adjustment of injection pressure, and check injector coupling or replacement.


3. Intake and exhaust system failure

The exhaust temperature is higher than that under normal conditions, and the smoke color is worse. 


1) Air filter obstruction

Exclusion methods: Clean the core of the air filter or remove dust from the paper filter, and replace it if necessary and check if the oil level is normal.



2) The exhaust pipe is blocked or the nozzle is too long, the turning radius is too small, and there are too many bends.

Exclusion methods: Remove carbon in exhaust pipe; reinstall exhaust pipe, not more than three bends, and have sufficient exhaust section.



4. Fuel injection advance or intake, exhaust phase change: the performance of the various speed deterioration.


Exclusion method: Check whether the two screws are loose at the propeller shaft of the fuel injection pump, and adjust the injection advance angle after the tightening, it is necessary to check the distribution phase and valve clearance.



5. Turbocharger failure: A drop in speed; a decrease in intake pressure; a leak or abnormal sound, etc.


1) Turbocharger bearing wear, rotor rubbing phenomenon

Exclusion method: Inspection and replacement of bearings


2) To contaminate, clog, or leak the inlet of a compressor or turbine.

Exclusion methods: Clean inlet, shell, wipe impeller; tighten joint nuts, clamps, etc.


6. Cylinder head assembly failure. At this time, not only the power is insufficient, the performance is degraded, but also there is air leakage, black smoke from the intake pipe, abnormal knocking sound and other phenomena.


1) The cylinder head leaks when combined with the body, and a stream of air flushes out of the liner when the speed changes. Cylinder head large stud nut loosened or liner damaged.

Exclusion methods: Tighten large stud nuts or replace cylinder head gaskets as required torque, and repair curettage joint if necessary.


2) The inlet and exhaust valve leak.

Exclusion methods: Check in, exhaust valve, repair valve and valve seat fit surface.



3) Valve spring damage

Exclusion methods: Replace damaged spring


4) Valve clearance is incorrect

Exclusion methods: Re calibration of valve clearance to specified values.


5) Oil injector hole leakage or steel washer damage; piston ring clamping rod bite caused cylinder compression pressure is insufficient.

Exclusion methods: Remove and repair. Clean and replace damaged parts.



7. Connecting rod bush and crankshaft connecting rod journal surface bite. There is abnormal sound, and oil pressure drop and other phenomena.


Exclusion methods: Remove side cover plate of diesel generator set, check the lateral clearance of connecting rod head, see whether the big end of connecting rod can move back and forth, if it can not move, it means gnawing, trimming the journal and replacing the connecting rod bearing bush.


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