Seven Reasons for Self-extinguishing Motor Vehicles

1. The oil return pipe joint bolts are installed in the wrong way. A tractor equipped with 495 diesel engine will be tested after major repair. The operator removes the air pump bleeder bolts and the air exhaust pump is always exhausted. The replacement of the diesel engine coarse and fine filter assembly and all the tubing fitting gaskets will not work. The reason: The oil pump return pipe joint bolts are wrong. The No. 1 pump is equipped with a pressure limiting valve at the return pipe joint. Only when the diesel oil in the oil gallery of the oil pump cover reaches a certain pressure, it begins to return oil. After mistakenly installing the general oil pipe joint bolt into the oil return port of the oil pump, when the hand oil pump pull button is lifted, the diesel oil in the oil pump is accompanied by the air sucked from the oil pump air release hole and enters the fine filter through the return oil pipe joint bolt. , and with the tank to join the oil into the pump inlet valve upper chamber. When the fuel pump pull button is depressed, the diesel in the upper cavity of the oil inlet valve passes through the outlet and enters into the oil pump inlet passage along with the air. In this way, there will be endless air. Replace the oil return pipe joint with limit pressure valve bolts, troubleshooting. 2. Severe wear of needle valve and valve hole A Changchun-12 small four-wheel tractor is all normal when traveling uphill and in peace, but as long as the downhill is loose, the diesel engine will automatically shut down. After a number of checks, it was found that the above fault was caused by severe wear of the needle valve and the valve hole. When the needle valve and valve hole are seriously worn, it will not only affect the quality of atomization, but also return oil, and it will cause air intake phenomenon. When the tractor is driving on flat ground and going uphill, there is high-pressure oil in the high-pressure oil path, there is no opportunity for air intake; when the tractor is on a downhill slope, a throttle is released and the high-pressure oil path is stopped, the high-pressure gas in the cylinder passes through the injector and The oil return pipe enters into the oil pipeline and the fuel injection pump, and the diesel engine turns off on its own. After replacing the nozzle, troubleshooting. 3. Deformation of the cylinder block causes the deformation of the cylinder liner. A Jiangling vehicle is running dry. As a result, the diesel engine holds the shaft at a high temperature. After the crankshaft, connecting rod, cylinder liner, piston, piston ring, and piston pin are replaced, they are often extinguished by themselves. Does not work properly. Symptoms of flameout: The diesel engine starts and accelerates. It is normal. After the engine is started for about 30 minutes, the rotation speed becomes unstable, and it turns off quickly. After the flameout, it can no longer be started. After the air is removed, the engine starts and accelerates to return to normal. After about 30 minutes of operation, the above symptoms were repeated. Based on the above symptom analysis, the initial judgment of the fault is caused by air entering the oil circuit. Further inspection found that a large amount of air bubbles existed in the fuel return pipe of the fuel pump during the period from engine instability to stall. Obviously, the judgment of the cause of the malfunction is correct. The question now is where the air comes from. First, verify the injector. If the needle valve is stuck in the open position, the high pressure air in the cylinder will flow back down the injector and enter the oil circuit. The verification results show that all 4 injectors are working properly. Second, check the oil inlet pipe for oil leakage. No oil leakage was found in the inspection results. The third step is to check if the low pressure oil line of the fuel injection pump leaks. Inspection results showed that the injection pump seals well. At this time, we noticed that the injection pump driving part of the diesel engine communicated with the timing gear chamber and also communicated with the oil pan. If the air pressure in the oil pan increases, the front oil seal of the injection pump camshaft can enter the fuel injection pump. For a diesel engine that has just replaced the piston connecting rod assembly, the reason for the increase in the air pressure in the oil pan is likely to be that the cylinder block is deformed after installation, causing serious under-exhaust. The lack of water in the vehicle causes the high temperature of the diesel engine, which should be the cause of deformation of the cylinder block. Then open the cylinder head, detect the cylinder liner diameter, found that each cylinder liner is out of round, but pulled out of the cylinder liner detection, but returned to normal. It can be seen that the fundamental reason for the self-extinguishing of the diesel engine is the deformation of the cylinder block. Because the cylinder sleeve is thin, it deforms with the deformation of the cylinder block after being pressed into the cylinder block. 4. After the flywheel gear ring pulls out a Dongfanghong-75 tractor and replaces the main clutch front driven plate assembly, the driver turns off when the clutch is depressed. The driver removed the inspection of the driven plate, and found that the new plate was 2 mm thicker than the old one (the thickness of the new plate was 14 mm, and the old plate was 12 mm). No other problems were found, but the failure persisted after the repair. After further inspection by the driver, only 7 mm of the flywheel ring gear was found. When the driven disc assembly was not replaced, the flywheel ring gear was out of order, but because the driven disc was thin, the clutch was depressed, and the flywheel was snagged before reaching the extent that the engine brake could be turned off. When the new driven plate assembly was replaced, the flywheel moved forward by 2mm due to the thickness of 2mm and the clutch was pressed. The flywheel was immediately on the flywheel housing and the engine was braked and turned off. After adjusting the flywheel ring gear to test, the fault disappeared. 5. Steel balls rust and springs are weak. A tractor of the Dongfanghong-75 suddenly turns off its own work. After checking the oil circuit, the operator confirms that there is no air in the oil path and starts the locomotive. When the auxiliary engine ignites, the main engine will ignite. When the auxiliary engine is separated from the main engine, the auxiliary engine is turned off and the main engine is turned off. . The operator removed the check of the pressure limiting valve on the pump head and found that the steel ball was rusted and the spring was weak. As a result, the oil pressure in the oil pump head was insufficient, and the host and the auxiliary machine were extinguished together. Clean the steel balls and springs, and then spring the seat cushions, repair and repair, the fault disappeared. 6. The pressure limiting valve of the low-pressure oil chamber of the fuel injection pump fails. A tractor of the Dongfanghong-802 type often fails to self-extinguish during operation. After inspection, the operator discovered that there was air in the fuel pump and it was difficult to remove. After careful inspection, the repairman found that the pressure limiting valve of the low pressure oil chamber of the fuel injection pump failed, causing the fuel from the fuel pump to enter the low pressure oil chamber and return to the oil pump through the pressure limiting valve. Because the oil pressure in the low pressure oil chamber was insufficient, the fuel injection pump was When the plunger is supplied with oil, a vacuum is instantaneously formed in the sleeve and the air is sucked from the outside. As time passes, the air resistance is generated, so that the fuel injection pump stops supplying oil, and the engine itself is turned off. Replace the pressure relief valve, troubleshooting. 7. The two fixing bolts of the fuel pump spline adapter fell off. A tractor of the Dongfanghong-75 suddenly turned off by itself during operation. The reason why the operator found the fault after multiple inspections was that the two fixing bolts of the fuel injection spline adapter fell off, the bolts on the transmission gear had been slipped, and the adjustment holes on the spline adapter plate had also become oval. Replace the drive gear and spline adapter, troubleshooting. Author: Heilongjiang Province A City Agricultural Machinery Supervision Station Heilongjiang Province A City Agricultural Machinery Promotion Station

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