The diesel generator set experiences poor combustion during use. The exhaust pipe of the diesel generator emits a "sudden" sound, and white smoke is emitted from the exhaust during idle. When the rated speed reaches 1500, the exhaust of the diesel generator still emits white smoke continuously, increasing but not decreasing.

1、 Cause of malfunction

1. Gas enters the oil circuit of the diesel supply mechanism, reducing the amount of oil in the fuel supply system, resulting in a small amount of oil in the high-pressure oil circuit.

2. The fuel injector of the diesel generator is damaged, the diesel atomization is not good, and the fuel injector drips oil. There are two possible reasons why the fuel injector drips oil based on past experience. Firstly, during the working steps of diesel generators, high-pressure diesel injected from the fuel injection device often carries some mechanical impurities into the fuel injector and adheres to the sealing cone of the needle valve body, making it poorly sealed; Secondly, due to the erosion of high-pressure and high-temperature gases in the combustion chamber, frequent erosion of mechanical impurities during combustion can cause pitting and pitting on the sealing ring of the needle valve and the needle valve body, leading to deterioration of the sealing performance between the fuel injector needle valve and the needle valve body and dripping of oil, resulting in poor combustion.

3. Damage to diesel high-pressure oil pump. The cylindrical pressure reducing ring belt and the oil outlet valve seat are severely worn, and the pressure reducing belt and the upper end of the valve seat are ground into a conical shape, resulting in excessive clearance. This way, when the fuel injection pump pumps oil, the pressure reducing belt will not fully expose the valve seat, causing a decrease in the oil pressure of the high-pressure oil pipe. In the second fuel injection, in order to increase the oil pressure in the oil pipe to the injection pressure, it takes up more fuel supply time, which delays the injection time, The amount of fuel injection has been correspondingly reduced, resulting in excessive residual diesel fuel in the high-pressure oil pipe when the high-pressure oil pump stops supplying fuel. The remaining oil pressure is too high, causing the fuel injection nozzle to spray unevenly and resulting in a situation of rear dripping.

4. Accident of low cylinder pressure. The cause of low cylinder pressure is that the gaps in each piston ring are aligned and not staggered; The piston ring is broken, and the cylinder is pulled; The valve spring suddenly breaks or the valve suddenly bites; Cylinder gasket malfunction, etc. If the pressure is insufficient, a large amount of white diesel vapor or oil mist will inevitably be discharged from the exhaust pipe, causing weak output of the diesel generator.

5. The fuel supply advance angle is too small. When installing the diesel generator, the timing gear mark and the high-pressure oil pump gear mark were not aligned, causing the high-pressure pump to supply oil too late.

2、 Inspection and handling measures

1. Firstly, start from the fuel supply mechanism to search for any gas leakage in the oil circuit of the fuel supply device, which reduces the fuel supply of the injector. After inspecting all the oil circuits from the oil tank outlet pipe to the high-pressure pump once, no looseness or rupture of the pipeline was found. To ensure that there is no air leakage in the pipeline, a new backup hand oil pump is used, and the "hanging bottle" scheme is adopted to directly supply fuel to the fuel pump without passing through the original diesel low-pressure pipeline. Even after starting, the diesel generator is still damaged, proving that the low-pressure fuel supply pipeline is in good condition.

2. Using the cylinder cut-off method, loosen the high-pressure oil pipe in front of the fuel injection pump in sequence, and inspect the combustion status of each cylinder of the diesel generator. It was found that the reaction of each cylinder was not very obvious. Remove the fuel injector and adjust it on the test bench. It was found that the atomization of each cylinder's fuel injection pump was poor, and the dripping situation was severe. Therefore, replace the fuel injection pump and correct the fuel injection pressure of the fuel injector to meet the working standard requirements. At the same time, use a cylinder gauge to measure the pressure of each cylinder. By checking that the pressure of each cylinder is within the normal range, there is no situation of low cylinder pressure. After installing the verified new fuel injector and restarting the diesel generator, it was found that the operation of the diesel generator had slightly improved, but still could not meet the working requirements. Due to the connection between the timing gear and the high-pressure pump gear not being disassembled, and the sudden malfunction of the diesel generator, the reason for the delayed ignition time can be ruled out.

3. In the combustion program of the diesel generator, there is no water spray phenomenon in the exhaust pipe, no bubbles or backflow in the anti rust water tank, and no shortage of coolant, indicating that the cylinder gasket has not been eroded.

After the above steps of accident clearance, it is suspected that there is a malfunction in the high-pressure pump. After removing the high-pressure pump and outsourcing the pump for calibration, it was found that there was significant wear between the distribution pump rotor and the sleeve, which caused a decrease in oil pressure and reduced oil supply to the oil pump. Therefore, the distribution rotor assembly was replaced, and after verification on the test bench, it was found that all fuel injection indicators were qualified. After installation, the diesel generator was restarted, but the diesel generator still could not accelerate the exhaust of white smoke. Open the cover of the timing gear chamber, check and confirm that there is no change in the fuel supply timing. After removing the high-pressure pump again, test it on the experimental bench and find that all indicators of the high-pressure pump are qualified.

4. After replacing the high-pressure pump of another normally used Isuzu diesel generator of the same type with this engine, start the diesel generator, and the exhaust pipe will no longer emit white smoke. The refueling speed will quickly increase and the operation will be strong. Therefore, it is confirmed that the original high-pressure pump is still damaged after calibration. So the high-pressure pump was completely disassembled and carefully cleaned. It was found that the front oil supply port of the distribution pump rotor was blocked by colloidal impurities, which hindered the normal oil supply of the distribution pump. When calibrating the pump on the pump test bench in the early stage, due to the fact that the oil pump used for adjustment testing is not exactly the same as the actual one used, especially the difference in the passing capacity and oil leakage degree of the valve and oil pipe, the high-pressure pump was qualified on the test bench, but the operation of the high-pressure pump was not qualified in actual work. After recalibration, the high-pressure pump was installed on the diesel generator and the damage was completely eliminated.

By analyzing the working mechanism and combining repair experience, all possible causes of the damage caused by the weak operation and white smoke emission of diesel generators were listed one by one. The fault was resolved through a path from external to internal, from easy to difficult, and from non disassembly diagnosis to disassembly diagnosis. Finally, the fundamental cause was found, which was the blockage caused by colloidal precipitates and impurities in diesel. Summarizing the steps taken to clear this accident, it can be seen that the cause of damage to diesel generators is often not a single one, but the result of multiple comprehensive functions. For example, the wear and replacement of fuel injectors discovered in the troubleshooting process, and the replacement of rotor distribution pump distribution rotor wear are also related to this accident. Extracting and summarizing the causes of diesel generator accidents, analyzing damage disposal methods, can provide strong reference value for diesel generator repair workers, and promote peer experience exchange.

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