Fault Analysis of Air Intake in the Fuel System of Diesel Generator Sets

Aug. 17, 2023

Once air enters the fuel system of a diesel generator, the engine is difficult to start, unstable to operate, or directly unable to start. Taking the most common plunger pump fuel supply system as an example, the following will systematically analyze various phenomena of air in the oil circuit.


1. If air enters the fuel supply system, the diesel generator will be difficult to start or easily stall.

Air has great compressibility and elasticity. When there is a leak in the oil pipe from the fuel tank to the diesel generator fuel pump section, air will seep in, reducing the vacuum in this section of the pipeline, weakening the suction of the fuel in the fuel tank, and even causing a cutoff, resulting in the engine being unable to start. In the case of less air mixed, the oil flow can still be maintained and sent to the fuel injection pump by the fuel transfer pump, but the engine may have difficulty starting, or it may self stop after being maintained for a short time after starting.


When a slightly higher amount of air is mixed in the oil circuit, it can lead to fuel cut-off or a significant decrease in fuel injection, making it impossible for the diesel generator to start at all.


2. How to find and repair leaks in pipelines.

The fuel supply system of diesel generators can be divided into low-pressure oil circuit and high-pressure oil circuit. The low-pressure oil circuit refers to a section of oil from the fuel tank to the low-pressure oil chamber of the fuel injection pump, while the high-pressure oil circuit refers to a section of oil from the plunger chamber in the high-pressure pump to the fuel injection nozzle. In the supply system of the plunger pump, there is no air infiltration in the high-pressure oil circuit, and there are leakage points that can only cause fuel leakage. Find a way to plug the leakage points. Below, we will focus on the leakage points in the low-pressure oil circuit.

Fault Analysis of Air Intake in the Fuel System of Diesel Generator Sets


Soft rubber hoses are mostly used in the low-pressure fuel supply system of diesel generators, which can easily cause friction with parts, resulting in oil leakage and intake. Oil leakage is relatively easy to find, while a damaged inlet in the pipeline is not easy to find. The following is a method for identifying the leakage point in the low-pressure oil circuit.


Method 1 to determine the leak point: exhaust the air in the oil circuit, start the engine, and find the location of the diesel leak, which is where the leak point is located.


Method 2 to determine the leakage point: Loosen the exhaust screw of the engine fuel injection pump and use a manual oil pump to pump the oil. If a large amount of oil bubbles are found to be discharging from the exhaust screw, and after repeated manual pumping, the bubbles still do not disappear, it can be determined that there is a leakage point in the negative pressure oil circuit between the fuel tank and the fuel delivery pump. The section of pipeline should be removed, then pressure gas should be introduced and placed in water to identify the location of the bubble, which is the leak point.


In addition to pipeline issues, various gaskets at pipeline joints can also leak due to improper installation, deformation, aging, and damage, becoming leakage points. Before conducting a detailed inspection of the pipeline, these nodes should be checked first.


The hard oil pipe outside the fuel tank is generally less prone to failure. If no leakage point can be found after the above inspection, it can be finally inspected.


The above is the fault analysis of the air intake in the fuel system of the diesel generator set, hoping to be helpful to you. Guangxi Dingbo Power Equipment Manufacturing Co., Ltd. is a generator manufacturer with 17 years of production and manufacturing experience. Our products have strong comparative advantages in terms of performance, price, after-sales service, and delivery time. If you are interested in diesel generators or would like to learn more about them, please feel free to contact us via email dingbo@dieselgeneratortech.com.

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