How to check the working condition of each cylinde

2022-07-24
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The proportion of exports to emerging countries will also be greatly increased. How to check the working condition of each cylinder of the diesel engine

when there is a fault in the cylinder of the diesel engine of construction machinery, there will be abnormal sound, abnormal smoke color and other phenomena. At this time, do not disassemble blindly to avoid wasting repair time and delaying production. The following methods can be used to analyze the fault position before maintenance

1. hearing judgment

touch a metal rod at the injector position of the cylinder head to listen to the working sound in the cylinder. If the condition is normal, it should be a crisp and uniform metal knocking sound. If the sound of a cylinder is low or discontinuous, it means that the oil supply is small or the combustion in the cylinder is poor; If the sound is rough, the fuel supply quantity may be too large or the fuel supply time may be too early. If the air inlet valve leaks, a "snap" sound can be heard at the air filter, and the temperature of the intake and exhaust manifolds of this cylinder is also higher than that of other cylinders; If the exhaust valve leaks, the high-temperature combustible gas in the cylinder will blow out, so the "fluttering" sound of leakage can be heard at the exhaust pipe of the cylinder. If the "shooting" of the exhaust pipe is caused by too late oil supply time, too much oil supply or oil dripping from the fuel injector, the exhaust pipe can also be seen to be on fire at night. If the valve clearance is too large, a regular "clicking" sound will be emitted during idling, especially when the engine is cold. If the fit clearance between the piston pin and the copper sleeve is too large, a light and rhythmic sharp sound will be emitted. The lower the speed, the more obvious the sound. In addition, if the fit clearance between the bearing bush and the crankshaft is too large, the diesel engine will make a heavy metal knocking sound when running at high speed

2. color observation and discrimination

for diesel engines that work normally, the smoke exhaust shall be colorless or light gray. If black smoke is emitted, it means that the diesel injected into the cylinder cannot be completely burned, so the exhaust gas contains a large amount of carbon particles. The main reasons are that the diesel engine is overloaded, the cylinder pressure is insufficient, the valve clearance is incorrect, the intake and exhaust system is not smooth, the oil supply is too large or the oil supply time is too late, the oil injector drips or atomizes poorly, and the diesel quality or brand is incorrect. If blue smoke is discharged, it means that excessive raw oil is saved from channeling into the cylinder for combustion. The main reasons are that there is too much oil in the oil pan or wet air filter, the piston ring is seriously worn, or the ring ports are in the same line, the clearance between the valve and the guide pipe is too large, or the diesel engine is put into heavy-duty work without full running in after overhaul. If white smoke is emitted, it indicates that the diesel oil contains moisture or the engine temperature is too low. If the smoke exhaust is intermittent, it means that the diesel oil in a cylinder has not been completely burned, so it continues to burn after entering the exhaust pipe. If there are water drops in the smoke exhaust, it means that water is entering the cylinder. Check whether the cylinder gasket is damaged and whether there are cracks in the cylinder head or cylinder wall. If the air filter exhausts smoke outward, the exhaust valve may not be opened, and the exhaust gas in the cylinder is forced to be discharged from the intake valve to the air filter through the intake pipe; At this time, the machine shall be shut down immediately to prevent the high-temperature exhaust gas from ablating the inlet valve and inlet valve seat and even the valve from falling into the cylinder and ramming the cylinder. Then, check whether the valve adjusting bolt is loose, whether the valve push rod is dropped and whether the valve rocker arm is broken

3. determination of cylinder disconnection

in order to determine which cylinder has fault, loosen the joint nut of high-pressure oil pipe cylinder by cylinder, and use the method of stopping oil supply for inspection. If the diesel engine speed drops after a cylinder is cut off, it indicates that the cylinder is working normally; If the speed change can not only save working time, it indicates that the cylinder is not working well. If the smoke exhaust does not disappear after the cylinder is disconnected, it indicates that the cylinder is working normally; If the smoke exhaust disappears, it indicates that the cylinder is faulty

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4. temperature sensing level

this inspection should be carried out after the cold start of the diesel engine. First, put the throttle at the medium and low speed positions, and touch the temperature of the exhaust manifold of each cylinder with your hand after idling for several minutes. If the temperature of a cylinder is lower than that of other cylinders, it indicates that the fuel supply of the cylinder is less or the diesel combustion is not good; If the temperature of a cylinder is too high, it indicates that the oil supply of the cylinder is too large

5. pulse size

when the diesel engine is running at the rated speed, hold the high-pressure oil pipe of a cylinder by hand. If you feel that the pulse momentum of the oil pipe is small, it indicates that the oil supply of the cylinder is low, or the injection pressure is low, or the atomization of the injector is poor; If the high-pressure oil pipe of a cylinder has a large pulse, it indicates that the oil supply of the cylinder is too large or the injection pressure is too high

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