How To Prevent Diesel Pump Plunger Wear

ForewordIn:  Recent years, the research on the wear and wear protection of components and parts has been gradually strengthened. Many countries in the world are intensively carrying out the research on wear and wear protection, because the research can greatly improve the life of diesel generator wearing parts and save materials. and energy. Taking the wear of the plunger and the sleeve as an example, the wear is mainly caused by the action of debris in the generator and the flushing of the high-pressure generator. Its common wear parts are the middle part between the top of the plunger and the spiral side and the periphery of the inlet and outlet of the sleeve. The finish is dull in color after wear.

Symptoms

There is a diesel generator with large vibration and abnormal exhaust sound. After stopping, the diesel generator runs smoothly at idle speed, and the diesel generator vibrates greatly when transitioning from idle speed to medium speed. It was preliminarily considered that the fuel injectors were not working well. For this reason, the 6 fuel injectors were removed from the diesel generator for cleaning and calibration. As a result, the 6 fuel injectors atomized well, and only the fuel injection pressure was different (the difference was about 1MPa ). Adjust the injection pressure of the 6 injectors to 25 MPa (specified as 24.5-25.3 MPa) by adjusting the thickness of the internal gasket. Loading test, the result is still faulty.

Fault Finding Analysis

According to the above fault symptoms, the problem may lie in the fuel injection pump (the fuel injection pump matched with the diesel generator is a VE distribution type fuel injection pump). Remove the fuel injection pump from the vehicle, after cleaning, install it on the fuel injection pump test bench for testing and inspection. It is found that the fuel supply volume of each cylinder is basically the same when the fuel injection pump is idling, but the fuel supply volume of the fuel injection pump at 800r/min is 4mL/100 times for the second cylinder, 8mL/100 times for the sixth cylinder, and 8mL/100 times for the other cylinders. The fuel supply is 7mL/100 times, and the fuel supply difference of each cylinder is relatively large, which is not a normal phenomenon, because the distribution type fuel injection pump has good fuel supply uniformity as a major feature of it. Disassembled this distributing fuel injection pump for inspection. It was found that the plunger was severely worn, and the edge wear of the oil inlet grooves on the plunger head was inconsistent, resulting in a large gap in fuel supply at the above-mentioned medium speed and unstable operation at medium speed. large vibration, and abnormal exhaust sound from the exhaust pipe.

Causes and troubleshooting

The specific reasons for the wear of the plunger and the sleeve are as follows:

• The diesel oil used has neither been filtered nor precipitated, so that the diesel oil contains more impurities.
• The diesel filter does not function as a filter. It should be replaced with a new one.
• The grade of diesel oil is not selected correctly. For example, diesel oil with too low viscosity is used when the temperature is high, which makes the plunger and sleeve poorly lubricated.
• The plunger coupling is not installed vertically in the fuel injection pump body and is easy to wear.
• The fuel injector or oil delivery valve is stuck in the closed position. In this way, when the fuel injection pressure of the injector is too high, the plunger continues to pump oil, causing the plunger to be damaged. According to the above inspection and analysis, a new pump head of the diesel generator set was replaced and debugged on the fuel injection pump test bench. After installation, the fault phenomenon of diesel generator is eliminated.

Precaution

• Save the spare diesel oil in advance. The purpose of doing this is to prevent water or very small debris from being injected into the diesel tank together with the diesel oil when filling the engine with diesel oil. If the filter protection measures in the fuel tank are not If it is complete, moisture or sundries may enter the plunger sleeve together with the diesel oil, causing abnormal wear of the plunger.
• Observe the oil level of the fuel tank as frequently as possible, so as to avoid the failure of fuel interruption during the operation of the diesel generator to the greatest extent, because if this happens, after the fuel is filled, the low-pressure oil circuit will There will be a lot of air, which will affect the starting of the engine. Therefore, the gas inlet must be vented at the oil inlet where the low-pressure oil pipe is connected to the diesel pump. If the cleaning work is not done well at this time, a small amount of oil or debris will enter the diesel pump, which will inevitably wear the plunger up.
• The diesel filter should be cleaned regularly. If it is not cleaned for a long time, the water or debris inside will be mixed into the diesel oil and enter the low-pressure oil circuit, causing wear to the plunger. The diesel filter element should generally be cleaned and replaced every 200 hours.
• Try to refuel at a reputable gas station, because the quality of the oil is also one of the reasons for the wear of the plunger.