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Why Is There Always Air In The Diesel Generator Oil Circuit System

Oct. 18, 2021

If the air in the oil circuit of the diesel generator cannot be discharged, after the generator set runs for a period of time, the exhaust of the exhaust pipe will change, white smoke will be emitted intermittently, the speed will drop, and the work will be weak. In severe cases, it is difficult to self-extinguish and start. The air in the oil circuit mainly comes from two sources.


(1) The low-pressure oil circuit sucks in air. Reasons for inhaling air in the low-pressure oil circuit:


1. When the diesel is used up, the vent on the fuel tank cap opens and air is sucked in.


2. The sealing gasket between the hand oil pump and the pump body on the oil transfer pump is broken or uneven, causing air to flow in.


3. The piston or cup of the hand oil pump is severely worn, and the air enters the low pressure oil circuit from the upper part of the hand oil pump through the gap between the piston or the cup and the pump barrel.


4. The sealing gasket of the oil pipe joint in the low pressure pipeline is uneven, damaged or the hollow screw is not tightened, and air flows into it.


5. The low-pressure fuel pipe of the fuel supply system ruptured, causing air to flow in. The inspection method for oil pipe damage is: remove the low-pressure oil pipe, wipe the joint, block one end of the oil pipe with your fingers, and use the mouth to exhaust the other end. If the tubing is not broken, a vacuum is basically formed in the tubing, and the tip of the tongue is sucked. If the tip of the tongue is always not sucked, the tubing is broken.


6. Mechanical impurities make the overflow valve not close tightly, causing the pressure in the fuel injection pump tubing to be too low, and the fuel injection pump tubing cannot be reduced.


diesel generator

(2) High pressure oil circuit enters gas. The high-pressure gas rushes back from the nozzle to the fuel supply circuit. At this time, if the nozzle needle valve is stuck in the open position, the oil outlet valve of the same cylinder is not tightly sealed, the needle valve and the guiding part of the needle valve body are severely worn, the high-pressure spring in the injector is broken, and the fitting hole of the injector tappet and the needle valve is worn out, then every time the cylinder works for one cycle, high-pressure air will enter the fuel oil circuit.


1. The reason for the high-pressure air flow fuel supply system: After the compression stroke of the diesel generator is completed, at a certain angle before the top dead center of the piston, the fuel injector sprays diesel to the cylinder. When the nozzle is opened, the gas in the cylinder forms a passage with the oil path (there is a pressure difference that varies with time between the gas in the passage). When the quality of the injector is not good, the high-pressure gas in the cylinder will flow from the nozzle through the sealing cone, through the gap between the needle valve of the nozzle assembly, the tappet hole in the injector body, and the fuel return pipe of the injector to flow back to the diesel filter. Until the oil circuit. Over time, the diesel supply will be blocked by gas.


For diesel generators whose oil return pipe is not directly connected to the diesel filter (take 4115 diesel generator as an example), high-pressure air can pass through the nozzle through the sealing cone, through the oil inlet hole, high-pressure oil pipe, oil outlet valve and the gap of the seat enters the nozzle cover, and returns to the oil transfer pump through the oil return valve hole on the pump cover.


2. The method to check whether the fuel injector is leaking: Connect the main return pipe of the fuel injector from the main return pipe of the diesel to make it communicate with the atmosphere, and then block the return pipe hole of the diesel filter to discharge the air in the oil circuit. Then start the diesel generator. If there is no gas in the fuel injection pump, it can be judged that the fuel injector is leaking.


At this time, all the oil return pipe joints of each injector should be removed to further determine which injector is leaking, if the oil return hole of a certain injector is gas, it can be judged that the injector has a leak fault.


For diesel generators that are not connected to the diesel filter, the fuel return pipe of the fuel injector can discharge air first, and then loosen the high pressure fuel pipe joints on the fuel injection pump one by one while the diesel generator is running. If a connector is loosened and continuously vented, it indicates that the injector is leaking.


Jiangsu Starlight Electricity Equipments Co.,Ltd. was founded in 1974, as a wholly-owned subsidiary of Jiangsu Starlight Power Group, it is one of the earliest manufacturers of generator sets in China. Starlight Power has 64 sales services, long-term technical advice for users, free debugging, free maintenance, free training services. For more details, please contact us with sales@dieselgeneratortech.com

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