Diagnosis and Treatment of Cummins Engine Low Speed and High Speed

by Starlight Generator dieselgeneratortech

1. Diagnosis and treatment of engine with normal low speed and short time high speed with too little smoke exhaust


The engine idle speed is good, and the throttle speed can be increased rapidly. However, the continuous boom throttle speed is not easy to rise, the driving is weak, or the medium speed is not able to drive. This is caused by insufficient low pressure oil supply.




a. Fuel filter or the oil-water separator is blocked.

b. Low pressure oil circuit is not smooth.

c. Insufficient oil supply in oil pump or the oil filter is blocked.

d. The inlet valve of fuel tank cover is invalid.


All of the above conditions can cause the fuel pressure of the low pressure oil chamber of the fuel injection pump to be insufficient, and only the oil supply amount required for the small load can be maintained. when It is necessary to use more oil supply for large and medium load, it cannot be satisfied, resulting in a weak driving.


Diagnosis and treatment


a. Check whether the intake valve of the tank cover is invalid, if it fails, a certain vacuum degree will be formed in the tank, and the diesel oil cannot be sucked out. Most of this phenomenon is caused by the loss of fuel tank cover and sealing with airtight plastic cloth.


b. Check if there is any concavity in the low pressure oil pipe and whether there is any blockage at the inlet pipe joint filter.


c. If the fuel filter or oil-water separator is not replaced for a long time, it should be replaced in time.


d. Check if the oil pump is working properly. If the oil supply is insufficient, replace or repair the oil pump in time.


2. Diagnosis and repair of low engine speed but no high speed, too little smoke exhaust


The low speed of the engine is good, but the speed can not be increased at the time of acceleration, and the driving is weak, which is caused by insufficient circulating oil supply.




a. The fuel injection pump is not adjusted properly, so that the fuel supply is reduced.


b. The governor spring is reduced in elasticity due to fatigue. When the throttle is stepped to the end, the oil adjustment lever can not move forward to the head, so that the fuel supply of the fuel injection pump is reduced and the engine cannot reach the rated speed.


c. The fuel pump plunger and the sleeve, the injector needle valve and the needle valve body are seriously worn, so that the diesel oil leakage increases when the oil is pumped, and the oil supply amount is relatively reduced.


d. Improper adjustment of the throttle control lever, or the accelerator pedal pin is too far, the accelerator pedal cannot be placed in place, resulting in too little oil supply at full load.


e. There is air in the oil circuit


Diagnosis and treatment


When the engine power is insufficient, if the low speed is good and the smoke exhaust is normal, it means that the engine burns well, that is, the diesel injection quality is good, the fuel supply start time is normal, the cylinder sealing is good and the intake air is sufficient.


a. In the case of normal low-pressure oil circuit, first check whether the degree of looseness of the accelerator pedal connecting pin and the length adjustment of the connecting rod are properly adjusted. When the throttle is stepped to the end and the governor arm is at the maximum position, the high speed limit screw should be in contact with the limit block. Otherwise it should be adjusted.


b. Drain the air from the oil circuit.


c. Debug the fuel injection pump on the test bench to eliminate the fault.


Hope the above methods can help you solve common problems about Cummins generator.

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About Starlight Generator Senior   dieselgeneratortech

176 connections, 3 recommendations, 624 honor points.
Joined APSense since, April 16th, 2017, From Guangxi, China.

Created on Sep 10th 2019 21:51. Viewed 377 times.


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