How to Prevent Internal Leaks in Diesel Generator Injectors
Diesel generator sets are essential equipment for many industrial and commercial facilities, and injectors are critical components of their fuel systems. Internal leaks in injectors can be difficult to detect visually, yet their impact is significant. Symptoms such as the generator failing to start, weak power output, air in the fuel lines, or even automatic shutdowns, as well as abnormal heating of the injector pump casing or oil pan, may indicate internal injector leaks. Here are six common leak points in diesel generator injectors and their detailed descriptions.
1. Leakage at the Plunger Sleeve Assembly Shoulder
The plunger nozzle sleeve's large cylindrical shoulder and the upper body of the pump have no sealing gasket; sealing is achieved through precision machining of the two mating surfaces. If there are noticeable compression marks on this tiny annular sealing surface, substantial diesel leakage may occur, preventing the generator set from operating properly. The unit may struggle to run at low speeds and may draw in air at higher speeds. This issue is primarily caused by excessive torque on the oil pressure adjustment seat and the fluctuating stress of high-pressure diesel during operation, accelerating fatigue strain.
Solution: Pay special attention to the torque setting of the oil pressure adjustment seat during installation and maintenance, ensuring the mating surfaces are free of compression marks. If compression marks are found, replace the damaged parts promptly.
2. Leakage Between Plunger and Plunger Sleeve

The fit between the plunger and plunger sleeve is extremely precise, with a clearance of only 0.002 to 0.003 mm. Impurities and moisture in the diesel can damage or corrode the plunger coupling, increasing the clearance and causing diesel leakage, preventing the generation of high-pressure diesel.
Solution: Regularly check and replace the diesel filter to ensure fuel cleanliness. Use high-quality diesel to avoid impurities and moisture entering the fuel system. Replace the plunger coupling immediately if wear or corrosion is detected.
3. Leakage at the Plunger Sleeve Positioning Screw

A pure copper gasket under the plunger sleeve set screw provides sealing. If this small gasket assembly leaks, frays, or cracks, diesel from the plunger sleeve will leak through the set screw.
Solution: Regularly inspect and replace the pure copper gasket to ensure it is intact. During installation, ensure the screw is securely fastened to prevent loosening.
4. Leakage from the Delivery Valve

If the copper (or nylon) gasket between the high-pressure oil chamber on the delivery valve and the large end face of the delivery valve seat breaks or deforms, or if the delivery valve seat is not tightened, the high-pressure oil chamber will connect with the low-pressure oil chamber, causing injector pump failure and preventing the generation of high-pressure diesel.
Solution: Regularly check the condition of the delivery valve gasket and replace it promptly if it is broken or deformed. Ensure the delivery valve seat is securely tightened to prevent loosening.
5. Leakage from the Return Oil Safety Valve

Multi-cylinder injectors have a return oil overflow valve to maintain the diesel pressure in the horizontal oil passage of the injector upper body above 150 kPa. If the return oil safety valve and valve seat are worn, rusted, have debris on the door, or experience return oil issues, the diesel pressure at the plunger oil inlet will decrease, drawing in air and causing the generator to fail to operate or shut down automatically.
Solution: Regularly inspect the return oil safety valve and valve seat, and clean any debris. Replace worn or rusted parts promptly. Maintain stable diesel pressure to prevent air from entering the system.
6. Leakage Between the Oil Pump Push Rod and Housing

If the plunger oil pump push rod and bushing are excessively worn or the push rod seal is damaged, the oil discharge volume will significantly increase. If the drain hole is blocked, some diesel will flow into the injector's oil passage, causing a leak.
Solution: Regularly check the wear of the push rod and bushing to ensure good sealing. Keep the drain hole clear to prevent diesel from flowing into the injector oil passage.
7. Maintenance and Care Recommendations

To prevent the aforementioned issues, the maintenance and care of diesel generator injectors are crucial. Here are some recommendations:
  • Regular Inspections: Regularly inspect each component of the injector to detect and resolve potential issues promptly.
  • Use Quality Fuel: Ensure the cleanliness of the fuel and avoid using diesel with impurities and moisture.
  • Replace Worn Parts: Replace worn parts, such as sealing gaskets and plunger couplings, in a timely manner to ensure the proper functioning of the injector.
  • Professional Maintenance: Have professionals conduct regular maintenance to ensure that all parameters of the injector meet standards.
By implementing these measures, internal leakage issues in diesel generator injectors can be effectively resolved, ensuring normal operation and extending the service life of the equipment. Regular maintenance and the use of high-quality fuel are crucial for preventing injector internal leaks. Establishing a comprehensive maintenance mechanism, timely replacement of worn parts, and clearing impurities can significantly enhance the efficiency and reliability of diesel generator sets, providing stable power supply for industrial and commercial facilities.
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