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Fault Analysis on Diesel Engine Failure to Start（5）
1. Inspection and recovery of individual cylinders of diesel engine not working
The failure of individual cylinders of the diesel engine is mainly caused by the abnormal operation of individual injectors.
Fault phenomenon: When the engine is working, the muffler makes a rhythmic "chugging" sound, emits black smoke, and the power drops. At this time, when the throttle opening is changed, the muffler will make a rhythmic "chunk" sound no matter what speed the engine is running. When idling, if the speed is slightly increased, the sound will be more obvious. Based on the above phenomenon, it can be determined that individual cylinders of the engine are not working.
How to determine which cylinder is not working: Use the cylinder cutting method. That is, use a wrench to loosen the high-pressure oil pipe and observe. If the engine speed does not change or changes little, it means that the cylinder is not working or not working well. If the engine speed changes significantly, it means that the cylinder is working well.
Failure analysis: The reason why some cylinders are not working is caused by the failure of the fuel system. If the diesel oil is mixed with water and impurities, or if the anti-rust oil is not washed out when replacing spare parts, it can cause the injector needle valve to get stuck, preventing the formation of oil mist, and making the cylinder unable to operate normally. In addition, the wear and tear of the high-pressure oil pump oil delivery valve coupling and the reduction of the opening pressure of the fuel injector coupling may cause the leaf oil nozzle to not work properly and cause the engine to work abnormally.
Troubleshooting method: Remove the faulty fuel injector assembly, install the fuel injector on the test bench, and press the test bench hand pump lever to cause the fuel injector to inject fuel. Check whether the opening pressure of the injector meets the requirements. The preload force of the pressure-regulating spring is changed by increasing or decreasing the pressure-regulating gasket in the injector, thereby adjusting the injector opening pressure. Adjust repeatedly to make the pressure gauge reading reach the specified opening pressure of the injector, and the diesel atomization is good, fine and even. If the injector is severely worn, the pressure cannot be adjusted, and the atomization is not good, the injector valve core should be replaced to ensure its pressure and atomization effect. If there is no problem with the fuel injector, you should also check whether the oil delivery valve coupling and oil delivery valve spring of the oil pump are broken. During the process of assembling the injector, pay attention to cleaning the injector mounting hole on the cylinder head. There should be no debris. During installation, place the copper gasket in accordance with the technical requirements. There should be no air leakage after installation.
2. The diesel engine speed is unstable when working
Fault manifestation: The diesel engine speed is unstable and the speed drops too much when the equipment is working.
Analysis of the reasons:
Oil leakage and air leakage in the oil inlet and return pipelines;
Blockage of the diesel filter element;
Insufficient fuel supply and poor diesel quality.
Solution:
Check the leakage fault point;
Clean the diesel coarse filter element and replace the diesel fine filter;
Tighten the oil pump belt; check the pressure and oil return volume of the diesel oil line at high idle speed. If the pressure is less than 5 bar, If the oil return volume is less than 8L/min, replace the oil transfer pump.
Maintenance suggestions: Ensure the quality of diesel and ensure sufficient oil quantity; regularly drain and sewage the diesel in the tank. Strictly implement the diesel engine maintenance regulations, replace the diesel fine filter and oil filter, and clean the diesel coarse filter within the specified time. Frequently check the moving parts of the diesel engine, especially the tension of the diesel delivery pump, fan, generator and water pump belt of the diesel engine.
