The forum friend “Chengdu fat man” encountered a wonderful problem when repairing a Hongyan Jieshi 6×4 dump truck. We analyzed it together in group Q for a long time. After we sorted out our ideas, we found the problem through gradual disassembly and inspection. This kind of engine damage accident caused by water inflow is by no means an exception in the dump truck working on the beach.
The car is a Hongyan Jieshi 6×4 dump truck. It pulls sand and gravel on the beach and starts with Koso 9 / 340 HP engine. The car owner complained about the car’s fault phenomenon. The cold start engine emits serious white smoke, which becomes blue smoke after reaching the normal operating temperature, accompanied by abnormal engine noise and insufficient power.
Check that the fuel injection nozzle is normal, and there is no fault display after detection with the diagnostic instrument. And there is no sign of cylinder gasket damage, oil and water do not cross, and the water tank has no bubbles. The car owner ran a lot of places without solutions. He was very distressed.
After listening to the owner’s fault description, according to the conventional thinking, first determine which cylinder has a problem; By first removing the exhaust manifold and then starting the engine, it is found that the sixth cylinder works poorly and the basic diesel oil is discharged without combustion during cold start; It is preliminarily determined that cylinder 6 works poorly, and it is suspected that the valves are poorly sealed or defective.
After determining that there is a problem with cylinder 6, open the cylinder head and check that the valve is intact. After removing the valve, it is found that the valve works well and the seal is tight; The cylinder gasket is not damaged, and the fault is not here.
Since it is not here, continue the inspection and analysis. When turning to check whether the piston of cylinder 6 has perforation or crack, it is found that the piston of cylinder 6 has no damage and perforation, but the piston can not reach the top dead center. There is still 3mm away from the top dead center. The fault point has been found.
The piston could not reach the top dead center, resulting in insufficient compression ratio and failure to reach the compression ignition temperature, so the cylinder did not work when the vehicle was cold, resulting in white smoke, so the piston connecting rod mechanism of cylinder 6 was disassembled and inspected; During disassembly and inspection, it was found that the connecting rod of cylinder 6 was bent and had interfered with the skirt of cylinder sleeve, resulting in the defect of cylinder sleeve skirt. After replacing the cylinder sleeve and piston connecting rod mechanism, the fault was eliminated.
Why does the connecting rod bend so badly? We can’t figure it out. After repeatedly questioning the owner, I found the problem. Before the fault, the engine was flooded because there was no time to evacuate the vehicle due to the flash flood; Check the water inlet of the engine oil after the water returns, and start the engine after changing the engine oil.
Did not check whether there was water in the cylinder. It was found that it was very difficult to start the engine, accompanied by the sliding phenomenon of the starter commutator. The sliding phenomenon of the starter commutator occurred before it was flooded. Therefore, insufficient attention was paid at that time. After replacing the starter commutator, the engine was forcibly started. Because water cannot be compressed, the piston top cylinder connecting rod is compressed and bent.
In summer, the sudden outbreak of mountain torrents and heavy rain in urban areas lead to the failure of timely drainage of rainwater, which makes the vehicles too late to evacuate and flooded from time to time. In most cases, after the water retreats, they do not pay attention to check whether there is water in the engine cylinder, but simply change the engine oil and the gear oil of transmission and main reducer.
As everyone knows, when the vehicle is flooded, water will pour back into the engine from the exhaust pipe. If the exhaust valve of a cylinder is open when the engine is stopped, the water will enter the engine. If it is forced to start again at this time, it is an inevitable consequence to damage the engine.
After the vehicle is flooded, be sure to check whether there is water in the cylinder. The method is very simple. Find a mechanic to remove the fuel injector and turn the engine for cylinder by cylinder inspection. If there is water, the water will be discharged from the fuel injector hole. After the inspection, there will be no problem to install the fuel injector and start the engine. Small actions can avoid large losses.
The working environment of the dump truck is relatively bad, especially the dump truck working in the river beach. In case of flash flood, it may be too late to transfer the car. After flooding, we must do a detailed inspection before starting the engine to avoid some unnecessary economic losses.
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