How to Deal with Air Ingress in Diesel Generator Fuel System
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During the operation of diesel generator set, difficulties in starting or abrupt shutdown shortly after starting are often attributed to air ingress into the fuel system. The presence of air can cause serious obstacles to the operation of diesel generators, causing the generator set to be difficult to start or run smoothly. To delve into this issue, this article will discuss in detail the causes, symptoms and solutions of air ingress in the fuel system, and provide effective preventive measures to help users better maintain and use diesel generator sets.
Causes of Air Ingress in the Fuel System
There are various reasons why air can enter the fuel system of diesel generator sets, seriously affecting the start and normal operation of the diesel generator.
1. Diesel Exhaustion
When the diesel runs out or the tank cap vent is blocked, a vacuum is formed in the tank and air is drawn into the fuel system. When there is a lot of air mixed in the fuel system, it will cause a number of cylinder blocks to cut off oil or significantly reduce the amount of fuel injection, and the diesel engine cannot start.
2. Issues with Transfer Pump
The sealing gasket between the hand primer pump and the pump body on the oil pump is broken or uneven, and air will escape from here. In addition, when the piston or leather cup is severely worn, air will enter the low-pressure fuel system from the upper part of the hand pump through gaps between the hand primer pump and the pump cylinder..
3. Fitting Problems in Fuel Lines
Imperfect or damaged sealing gaskets in fittings along the low-pressure fuel lines, or improperly tightened hollow screws, can cause air ingress. A rupture in the low-pressure fuel line supplying fuel to the fuel delivery system can also introduce air.
4. Return Valve Issues
Mechanical impurities can prevent the proper closure of the return valve, causing diesel to discharge through it. This lowers the pressure in the injector fuel path, reduces fuel delivery, and prevents the expulsion of residual air from the fuel system.
Symptoms of Air Ingress in the Fuel System
The presence of air in the fuel system of diesel generator sets manifests in several noticeable ways.
Difficulty in Starting: Air reduces the vacuum in the fuel system, weakening the suction force of fuel from the tank, thereby preventing smooth engine starting.
Unstable Operation: With a small amount of air mixed in the fuel flow, the fuel can still be delivered to the injectors by the transfer pump. However, the engine may have difficulty starting or may shut down shortly after starting.
Severe Starting Issues: A significant amount of air in the fuel system can lead to reduced fuel delivery to multiple cylinders or injectors, rendering the diesel engine unable to start.
Corresponding Effective Solutions
To address the challenge posed by air ingress in the fuel system of diesel generator sets, the following solutions are recommended:
1. Air Bleeding from the Fuel System
Using Bleed Screws: Unscrew the bleed screws on either side of the injector several turns using a screwdriver or spanner. Continuously press the hand primer pump until air-free diesel is expelled and a chirping sound is heard. Then tighten the bleed screws and return the hand primer pump to its original position.
Fitting Junction Method: If suitable tools like screwdrivers or spanners are unavailable, first unscrew the hand primer pump. Then loosen any junctions between the diesel filter and injectors. Repeatedly press the hand primer pump until the junction expels air-free fuel. While pressing the hand primer pump, secure the junction. Finally, return the hand primer pump to its original position.
Overflow Valve Method: When unable to loosen junction screws, repeatedly press the hand primer pump until the pressure in the low-pressure fuel system between the transfer pump and injectors is sufficiently high. Fuel flowing into the overflow valve will expel air from the system.
Driving Mechanical Transfer Pumps: To eliminate air from the fuel system, first loosen the bleed screws on the injectors or loosen any junction between the diesel filter and injectors. Start the mechanical transfer pump, and fuel should spray out from the leakage point without air bubbles. Tighten the loosened leakage point to expel all air from the fuel system.
2. Identifying Leaks in the Fuel Lines
Check for Oil Leakage Points: After eliminating air from the fuel system, start the engine and locate the leaky fuel spots.
Exhaust Bubble Inspection: Loosen the bleed screw on the injector pump and manually pump the fuel. If a large number of air bubbles appear at the bleed screw and do not disappear after repeated manual pumping, there may be a leak in the vacuum fuel system from the tank to the pump.
Check Gaskets: In addition to pipeline issues, various gaskets at pipeline junctions can cause air leaks due to improper installation, deformation, aging, or damage.
Preventive Measures
To prevent air ingress into the fuel system of diesel generator sets and ensure their smooth operation under various conditions, the following preventive measures are crucial.
Regular Inspection of Fuel Tanks and Lines: Ensure the vent hole in the fuel tank cap remains clear to prevent vacuum formation. Regularly inspect seal gaskets in transfer pumps and hand primer pumps to prevent rupture or unevenness.
Maintenance of Fitting Junctions: Regularly inspect sealing gaskets in fittings along low-pressure fuel lines to ensure they remain intact. Replace damaged gaskets promptly and tighten hollow screws securely.
Cleaning of Return Valves: Regularly clean return valves to prevent mechanical impurities from causing improper closure. Ensure normal pressure in the injector fuel path to prevent residual air in the fuel system.
Regular Maintenance of Injectors: Regularly maintain all injectors and repair or replace needle valve components as needed to prevent inadequate sealing due to wear.
In conclusion, air ingress into the fuel system of diesel generator sets significantly impacts engine performance and reliability, causing difficulties in starting and unstable operation. Therefore, regular inspection and maintenance of the fuel system, especially critical components such as transfer pumps, injectors, and fuel line fittings, are essential measures to ensure smooth operation. By implementing effective preventive measures and timely repairs, the risk of air ingress into the fuel system can be significantly reduced, thereby safeguarding the reliability and stability of diesel generator sets.
