When a Diesel Generator fails to produce its specified power

Updated: Sep 23, 2020

Reason One: Failure to produce the specified power due to insufficient compression pressure. 


There is a possible air leakage at the sealing part of the cylinder head and the engine body, which shows that a stream of air flow is seeping out of through the diesel generator gasket when there is a change in speed, or the cylinder head is loose or has come loose causing the same... possible other reason for the same could be that one of the piston ring is stuck, the valve stem is jammed, and the power generator cylinder head injector is leaking from its thread, also possible is that the copper washer of the the injector is damaged, the joint surface of fuel injector and fuel injector body is damaged.

How to Fix:

Check the joint surface of cylinder head and engine body, replace the cylinder gasket, clean or repair any of the above mentioned, replace piston rings jammed or damaged, clean the seat of the injector, tighten the fuel injector tight cap or grinding plane.

Reason 2: Failure to produce the specified power due to over high Coolant temperature.


Diesel engine overheating (cooling or lubrication system failure).

How to Fix:

Overhaul the cooling and diesel generator lubrication system and remove scale from the water jacket, cleaning the oil cooler.

Reason 3: Failure to produce the specified power due to abnormal oil supply and fuel system failure.


Possible Air intakes false air into the engine oil system

Possible Fuel injection pump failure

Possible Injector failure.

How to Fix:

Release air from the fuel system;

Repair or replace parts;

Repair or replace parts of injection.

If we want to know whether the diesel generator produce specified power, we need to know how many kinds of power of diesel genset:

Continuous power (COP): the maximum power which under agreed operating maintenance conditions and in accordance with the manufacturer’s specifications, the generator is continuously operated at constant load and the maximum number of operating hours per year is unrestricted.

Perkins Generator Turbo System

Prime power (PRP): the maximum power at which the generator operates continuously at variable load and unlimited operating hours per year under agreed operating conditions and maintenance as specified by the manufacturer. The average power output during the 24-hour operating cycle shall not exceed 70% of the basic power unless agreed with the engine manufacturer. Continuous power (COP) shall be used in applications where the allowable average power output is required to be higher than the specified value. The unit is called rated prime power diesel generator set.

Emergency standby power (ESP): the maximum power which under the agreed operation conditions and in accordance with the manufacturer’s regulations for maintenance, once the main power supply grid is interrupted or under the experimental conditions, the generator operates with variable load and the operation time reaches 200h per year. The average power output allowed during the 24-hour operating cycle shall not exceed 70% of the emergency standby power unless agreed with the engine manufacturer. The unit is called emergency standby power diesel generator set.

Limited running time power (LRTP): the maximum power which under the agreed operation conditions and in accordance with the Diesel Generator manufacturer’s regulations for maintenance, the operation time of diesel generator can reach 500h per year. In accordance with 100% limited running time power, the diesel generator set can operate 500h per year.

The standard also specifies the site conditions for the operation of the generator set: the site conditions are determined by the user. If the site conditions are unknown and there are no other regulations, the following rated site conditions should be adopted:

1. Absolute atmospheric pressure: 89.9kPa (or altitude of 1000m)

2. Ambient temperature: 40 ℃

3. Relative humidity: 60%.

In generally, output power calibrated on generator set nameplate is divided into continuous power, prime power and standby power.

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