Common Fuel Injection Pump Leaks in Diesel Generators

The fuel injection pump is a crucial component of the diesel generator's fuel system. It is responsible for injecting diesel into the engine's combustion chamber at high pressure, ensuring the smooth operation of the diesel engine. The performance of the fuel injection pump directly affects the generator's startup, power output, and long-term operational stability. However, due to the complex internal structure of the pump, many leakage issues are difficult to detect with the naked eye. When a diesel generator experiences difficulty starting, insufficient power, air in the fuel system, or the engine shutting off automatically, it is often caused by leakage in the fuel injection pump. Identifying and repairing these leaks promptly is key to ensuring the normal operation of the diesel generator.

Common Leakage Points in Fuel Injection Pumps

The fuel injection pump has a complex internal structure, and leaks can occur at various points. Here are the six most common leakage areas in diesel generator fuel injection pumps and their effects.

1. Leakage at the Plunger Sleeve Installation Shoulder

The plunger sleeve installation shoulder is a common leakage point. Unlike traditional seals, this part relies on precisely machined mating surfaces to form a seal, which is very narrow and can be easily damaged. If there are signs of compression marks at the installation shoulder, it can cause a significant diesel leak, disrupting the generator's operation. At low speeds, the engine may still work, but as speed increases, air may be drawn into the system, causing the engine to shut down. This problem is usually caused by excessive tightening torque on the fuel pressure regulator seat or increased fluctuations in the high-pressure diesel.

2. Leakage Between the Plunger and Plunger Sleeve

The fit between the plunger and the plunger sleeve is extremely precise, with a gap typically only 0.002–0.003 mm. This tight fit ensures efficient diesel pressurization. However, if the diesel fuel contains impurities or moisture, it can lead to wear or corrosion of the plunger and sleeve surfaces, increasing the gap. This results in insufficient pressurization of the diesel, causing the injection pump to fail in generating enough pressure, which in turn affects engine performance and may even prevent the engine from starting.

3. Leakage at the Plunger Sleeve Positioning Screws

The plunger sleeve is fixed to the pump body with positioning screws, which are sealed by a copper washer. If the washer is installed incorrectly, worn, or cracked, it can cause diesel to leak from the screw area. This type of leak typically occurs under high-pressure conditions and affects the proper operation of the injection pump, leading to insufficient power and unstable operation of the diesel generator.

4. Leakage at the Fuel Outlet Valve

The fuel outlet valve is responsible for delivering high-pressure diesel to the injector. If the gasket (such as copper or nylon) on the outlet valve breaks or deforms, or if the valve seat is not properly tightened, the high-pressure and low-pressure chambers may connect, preventing the generation of sufficient high-pressure diesel. This can lead to starting difficulties, low power, and, under high load, engine stalling. Ensuring the seal integrity of the outlet valve is therefore critical.

5. Leakage at the Return Oil Overflow Valve

The return oil overflow valve maintains the proper pressure in the fuel injection pump's oil system. If the valve or seat is worn, corroded, or has impurities, it can cause insufficient diesel pressure and may introduce air into the system. When air enters the system, the injection pump fails to supply enough diesel, leading to engine startup problems, unstable operation, or even automatic shutdown. This issue is particularly common in multi-cylinder fuel injection pumps and has a serious impact on engine performance.

6. Leakage Between the Oil Pump Push Rod and Bushing

The precise fit between the oil pump push rod and the bushing is essential for the proper functioning of the injection pump. If the push rod or bushing becomes excessively worn, or if the push rod seal is damaged, it can increase the amount of oil discharged, causing diesel to leak into the injection pump's oil system and destabilize the oil pressure. If the oil drain holes become blocked, the leaking diesel can worsen the internal pressure instability of the pump, leading to the failure of the diesel generator.

Hazards of Fuel Injection Pump Leaks

Although leakage in the fuel injection pump may seem like a minor issue, the consequences can be severe. Any leak can cause pressure instability in the fuel system, which in turn affects the diesel generator's power output, leading to starting difficulties, power loss, unstable operation, or even stalling in extreme cases. Leaks also waste diesel, increasing fuel consumption and reducing engine efficiency.

How to Solve Fuel Injection Pump Leakage Issues

If leakage is detected early and the affected areas are properly diagnosed, the problem can generally be resolved. Maintenance personnel should master effective leakage inspection methods and regularly check key areas of the injection pump, especially high-pressure components like the plunger sleeve, plunger, return oil overflow valve, and outlet valve. If leakage is found, appropriate repairs should be carried out, such as replacing damaged gaskets, repairing worn parts, and cleaning the fuel system.
In addition, regular maintenance of the fuel injection pump, such as changing the filters, cleaning the fuel system, and checking oil pressure, can effectively prevent leakage issues, extend the life of the diesel generator, and improve its operational efficiency.

Conclusion

The fuel injection pump is a critical component of a diesel generator's fuel system. Although leakage problems may seem small, their impact on the operation of the diesel generator cannot be overlooked. Understanding the common leakage points, causes, and solutions is key to ensuring the long-term stable operation of the diesel generator. Regular maintenance and timely repairs will ensure the proper functioning of the fuel injection pump, improving the efficiency and reliability of the diesel generator.