What Causes Cummins Diesel Generator Failure to Produce Specified Power

by Generator D. Diesel Generator

When diesel generator set is failure to produce specified power, firstly we should check whether air intake and fuel injection are sufficient, whether the combustion process is normal and the compression pressure is large enough to analyze and judge step by step, find out the cause of the fault and eliminate it.

The specific causes and solution methods are as follows:

1.Failure to produce specified power due to failure of valve mechanism and air inlet and exhaust system.


Incorrect clearance between intake, exhaust valves and rocker arms;

Incorrect actual opening and closing time of intake and exhaust valves;

Valve spring is damaged;

The valve has carbon deposits and the sealing surface leaks;

Air filter blocked;

Exhaust pipe and silencer have serious carbon deposits and poor exhaust.

Treatment methods:

Check and adjust to specified clearance;

Check and adjust the opening and closing time of intake and exhaust valves;

Replace new valve spring;

Remove the carbon deposit and grind the valve;

Clean air filter and remove carbon deposit.


2.Failure to produce the specified power due to insufficient compression pressure.


There is air leakage at the sealing part of the cylinder head and the engine body, which shows that a stream of air flows out of the gasket when changing speed, and the big nut of the cylinder head is loose;

The piston ring is stuck, the valve stem is not flexible, and the cylinder head injector hole is leaking. The copper washer of the tight cap of the injector is damaged, and the injector hole plane is not cleaned;

The joint surface of fuel injector and fuel injector body is damaged.

Treatment methods:

Check the joint surface of cylinder head and engine body, replace the cylinder gasket, clean and repair;

Replace piston ring;

Clean the seat hole;

Tighten the fuel injector tight cap or grinding plane.

3.Failure to produce the specified power due to over high water temperature.


Diesel engine overheating (cooling or lubrication system failure).

Treatment methods:

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

4.Failure to produce the specified power due to abnormal oil supply and fuel system failure.


Air intakes into oil system;

Fuel injection pump failure;

Injector failure.

Treatment methods:

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.


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 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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About Generator D. Senior   Diesel Generator

111 connections, 1 recommendations, 676 honor points.
Joined APSense since, September 11th, 2017, From Jiangsu, China.

Created on Oct 22nd 2019 21:58. Viewed 272 times.


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