Diagnosis Of Internal Leakage In Fuel Injection Pump Of Diesel Generator

Internal leakage occurs in the diesel generator fuel injection pump, which is generally difficult to detect with the naked eye. If the diesel engine is difficult to start, the power drops, the oil circuit has endless air, and sometimes it automatically shuts down, and the oil level in the fuel injection pump housing or oil pan rises abnormally, it can be diagnosed as an internal leakage of the fuel injection pump.

The main parts of the leakage in the fuel injection pump are as follows:

1. There is leakage at the installation shoulder of the plunger sleeve. There is no sealing gasket between the large cylindrical shoulder of the plunger sleeve of the plunger type fuel injection pump and the upper body of the oil pump, and the sealing is realized by the fine machining of the two joint surfaces. This is an annular, small-area sealing plane. If there are obvious extrusion marks here, it will cause a large amount of diesel leakage, which will make the diesel engine unable to work normally. The main reason for the extrusion marks on the installation shoulder of the plunger sleeve is that the torque for tightening the oil outlet valve seat is too large, and the fluctuating stress of the high-pressure diesel oil during work will also accelerate the fatigue damage here.

2. There is leakage between the plunger and the plunger sleeve. The cooperation between the plunger and the plunger sleeve was originally very precise, and the gap was only 0.002-0.003mm. After the two have been selected and ground, the surface roughness and precision are particularly high. In use, if the diesel oil contains impurities and moisture, it will cause wear or corrosion of the plunger coupler, the gap will increase, and the diesel oil will leak, so the high pressure of the diesel oil cannot be established.

3. Oil leakage at the positioning screw of the plunger sleeve. There is a 1mm thick pure copper pad under the positioning screw of the plunger sleeve, which mainly plays the role of sealing. If this small gasket is missing, or it is fluffed or cracked, the diesel fuel in the plunger sleeve will leak from the set screw.

4. The oil outlet valve leaks. When the pure copper (or nylon) sealing gasket between the oil outlet valve seat and the large end face of the oil outlet valve seat is broken or deformed or the oil outlet valve seat is not tightened, the high pressure oil chamber above the oil outlet valve will be connected with the lower pressure oil chamber. The cavities are connected, so that the fuel injection pump cannot produce high-pressure diesel.

5. The oil return overflow valve leaks. The purpose of setting the oil return relief valve in the multi-cylinder fuel injection pump is to maintain the pressure of the diesel oil in the horizontal oil passage of the upper body of the fuel injection pump above 150kPa. If the oil return relief valve and valve seat are worn or corroded, the reading door is cushioned by debris, or there is oil return phenomenon, the diesel pressure at the oil inlet of the plunger sleeve will drop, or air will be sucked into the fuel injection pump, resulting in the inability of the diesel engine to work. It even shuts off automatically.

6. Oil leakage between the push rod of the oil pump and the bushing. When the plunger type oil pump push rod and bushing are worn out or the sealing ring on the push rod is damaged, the oil leakage will increase greatly. If the oil drain hole is blocked, this part of the diesel will flow into the oil passage of the fuel injection pump.

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