Fault Modes of Diesel Engine Mechanical Fuel Injection System 1

The main factors that cause diesel generator failures in the mechanical fuel injection pump fuel supply system of diesel engines are as follows:

(1) Three pairs of precision components are worn. During the operation of diesel generators, faults in the fuel supply system often occur in three pairs of precision components (namely plunger components, oil outlet valve components, and injector needle valve components) in the high-pressure fuel circuit system. These three pairs of precision components are key components of the entire fuel supply system, and their performance directly affects the working performance of the system and even the entire diesel generator.

1. Plunger parts: Plunger parts are usually ground and selected, so their accuracy is high, their roughness is small, and the fit gap between the two is very small. In use, due to the erosion of high-speed, high-pressure, and diesel with mechanical impurities, wear will occur when the plunger moves back and forth. After the wear of the plunger coupling, the gap between the plunger and the sleeve increases, causing an increase in oil leakage and resulting in changes in the fuel supply and injection patterns. As a result, the fuel supply time is delayed, the fuel supply quantity is reduced, the starting and ending fuel injection speeds are reduced, the fuel injection duration is increased, and the fuel spray is poor, causing the diesel engine to emit black smoke at low loads or even idle. In addition, due to the leakage of plunger fuel supply, the fuel supply is insufficient, the injection pressure is reduced, and thus the power of the diesel engine is reduced. Due to the decrease in injection pressure, it can also make the fuel injector prone to carbon buildup and jamming.

2. Oil outlet valve coupling: The oil outlet valve coupling is very precise, and its wear area is on the sealing cone surface of the oil outlet valve. This is due to the reflection and residual pressure of the oil outlet valve spring and the high-pressure oil pressure wave in the high-pressure oil circuit during the pressure reducing effect of the oil outlet valve, which causes the valve core to collide with the sealing cone of the valve seat, as well as the effect of impurities in diesel. After the sealing cone surface of the oil outlet valve wears out, it loses its sealing effect and will cause irregular backflow oil leakage in the high-pressure oil pipe, resulting in a decrease and instability of residual pressure in the high-pressure oil pipe, leading to a serious decrease in oil supply or even no oil supply. Due to the wear of the sealing cone surface of the oil outlet, the quality of fuel atomization decreases and fuel injection is delayed, resulting in a deterioration of the combustion process of the diesel engine and a decrease in its performance indicators. The wear of the pressure reducing ring and the seat hole is caused by the grinding of mechanical impurities trapped in the gap when the pressure reducing ring enters the seat hole after cutting off the oil supply. After the wear of the pressure reducing ring and seat hole, the clearance increases, and the lift of the oil outlet valve decreases during the fuel supply process. The pressure reducing effect decreases during the unloading process, resulting in high residual pressure and large pressure waves in the high-pressure oil pipe. The fuel supply increases, and the fuel supply stops not quickly, which may form a single injection, causing poor spraying and dripping, incomplete combustion, and rough operation of the diesel engine, resulting in a decrease in power. The guide part and seat hole of the oil outlet valve are generally worn lightly, and the gap increases after wear. When the oil outlet valve moves up and down, it will shake, affecting the alignment of the conical surface, reducing the sealing performance, and causing eccentric wear of the pressure reducing ring. For multi cylinder diesel engines, the degree of wear on the output valve or plunger components varies, resulting in uneven fuel supply, inconsistent fuel injection pressure and advance angle, and causing unstable diesel engine operation.

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