The engine no longer has any cylinders.
When the engine runs out of cylinders, problems such as loud engine noise, unstable idling speed and abnormal body vibration will occur. In this case, check the condition of the cylinder and the working condition of the spark plug. When the engine is running, the piston skirt collides with the cylinder wall, producing a clear "dang-dang" sound, which is usually more obvious at idle or low speeds.
The abnormal noise in the cylinder of the diesel generator set engine can be summarized as the sound of piston knocking on the cylinder, piston pin knocking, etc. impact of the top of the piston against the cylinder head, impact of the top of the piston, and knocking of the piston rings. There are several types of noises, including valve knock and cylinder knock.
1. The impact sound of the top of the piston and the cylinder head
The abnormal sound of the top of the piston hitting the cylinder head is a continuous metallic knock. "tat-tat-tat" sound There is a clicking sound, especially at high speed. The source of the abnormal noise is in the upper part of the cylinder, the sound is solid and loud, and the cylinder head vibrates. The main reasons are as follows.
(1) The crankshaft bearing, connecting rod bearing and piston pin hole are severely worn and the corresponding clearance greatly exceeds the standard. As the piston stroke changes, the top of the piston hits the. cylinder head under the action of the force of inertia.
(2) Due to the incorrect installation of other pistons with similar specifications when replacing the piston, or counterfeit and substandard products, the distance between the center line of the hole of the piston The piston pin and the upper surface of the piston are larger than the original piston, causing the piston to reach top dead center. Collisionwith the cylinder head due to excessive height.
If you encounter such a situation while driving, the first aid method is to remove the cylinder head and add a cylinder gasket to lift the cylinder head to avoid collision again. However, when repair conditions exist, repairs must be carried out immediately to restore its good technical condition.
2. Abnormal noise at the piston ring area
Abnormal noise at the piston ring area mainly includes the metal knocking noise of the piston ring and air. Piston ring leak. Abnormal noise and noise caused by excessive carbon deposits.
(1) Metallic knocking noise from the piston rings. After prolonged operation of the engine, the cylinder wall is worn, but the upper part of the cylinder wall which is not in contact with the piston ring remainsalmost dreams its original geometric shape and size, which creates a step on the cylinder. wall. If an old cylinder seal is used or a new one is too thin, the working piston ring will collide with the cylinder wall step, producing a dull metallic impact noise. If the engine speed increases, the abnormal noise will also increase. In addition, if the piston ring is broken or the gap between the piston ring and the ring groove is too large, it will also cause a loud knocking noise.
(2) The sound of air leaking from the piston ring. The elasticity of the piston ring is weakened, the opening space is too large or the openings overlap, and the cylinder wall has grooves, etc., which will cause the piston ring to leak. The sound is a "drinking" or "hissing" sound, and when there is a large air leak, it will make a "hissing" sound. The diagnostic methodconsists of stalling the engine when the water temperature exceeds 80°C. At this time, you can inject some fresh, clean engine oil into the cylinder, rotate the crankshaft for a few revolutions, then restart the engine. Appear, it can be concluded that the piston ring is leaking.
(3) Abnormal noises caused by excessive carbon deposits. When there is too much carbon deposit, the abnormal noise coming from the cylinder is a high-pitched sound. Because the carbon deposit is burned red, the engine exhibits symptoms of premature ignition and is difficult to stall. The formation of carbon deposits on the piston ring is mainly due to lax sealing between the piston ring and the cylinder wall, excessive opening clearance, reverse installation of the piston ring, overlapping of ring holes, etc., resulting in lubricating oil leakage. escape upwards and gases at high temperatures andHigh pressure escapes downward, causing carbon deposits to build up in the piston. The ring part burns, causing carbon deposits to form and even stick to the piston ring, causing the piston ring to lose its elasticity. sealing effect. Generally, this fault can be eliminated after replacing the piston ring with a suitable specification.
3. Cylinder knocking noise
Cylinder knocking refers to when the piston begins its working stroke, or when the piston rises, the piston is in the cylinder The resulting rocking causes the head and skirt to collide with the cylinder wall, causing an abnormal "popping" or "clicking" sound. If there is a “dang-dang” noise, it is mainly due to poor cylinder wall lubrication. At this time you can pour some oil into the cylinder and restart the engine. If theAbnormal noise is reduced or disappears. this means that the abnormal noise is indeed caused by poor lubrication. If there is a "click" and blue smoke coming from the exhaust pipe, this is usually due to too large a gap between the piston and the cylinder wall. The main reasons for the above situation are as follows:
(1) If this phenomenon only occurs after the car is started from cold. It will disappear automatically when the water temperature reaches normal operation. This is because the fit gap between the piston and the cylinder wall is too large. When the car is cold, the piston shrinks, further increasing the adaptation gap between the two. with an obvious knocking noise. Once the machine temperature rises, the piston expands and the deviation tends to the normal value, so the abnormal noise disappears. This situation will not pose any major problems in the short term.t term.
(2) The quality of the engine oil does not meet the requirements. When the engine restarts after a long period of stalling, the engine oil is viscous and not very fluid. A good oil film cannot form. the cylinder wall in a short time, and the piston and the cylinder wall are directly connected. The collision causes the cylinder to knock. After a period of operation, the viscosity of the lubricating oil will be normal, an oil film will form on the cylinder wall, and the abnormal noise will weaken or disappear. As long as the lubricating oil is correctly selected, the engine crankcase is preheated before starting and lubricated with mixed oil, then press the starting lever several times before starting to allow more lubricating oil to adhere to the machine parts. Avoidable.
(3) The mixture entering the cylinder cannot burn normally, resulting in pre-ignition ou an explosion, or when the accelerator is pressed hard while the engine is empty, the noise of the piston and a collision between the walls of the cylinder will be produced. The engine should operate at normal temperature, use gasoline that meets octane requirements, and adjust the ignition timing accordingly.
(4) The piston skirt is worn and the cylindricity error is too great. As the piston moves upward, its top hits the cylinder wall. The piston and cylinder are badly worn and the space between them. two, it's small. It can be inspected after disassembly and corresponding repair measures can be taken depending on the situation.
(5) Due to the bending and twisting of the connecting rod, the deviation of the piston pin and the pin hole, the non-parallel axes of the crankpin and the pin piston, etc., it the piston will also flex in the cylinder and strikera the cylinder wall. thisIn this case, it can only be inspected after disassembly, and the corresponding parts can be replaced after diagnosis.
4. The knocking noise of the piston pin
Piston pin and piston pin hole, piston pin and big end bushing (or bearing) If the gap is too large, a sharp, sharp, sharp metal knocking sound will be emitted, similar to the sound of a small hand hammer hitting an iron drill. The rule is that the engine does not make noise when it is cold and starts, but it makes noise when the temperature rises, and the higher the temperature, the louder it becomes. If the ignition time is advanced, the sound will speed up and become louder. If the spark plug is cut, the sound will weaken or disappear.
Some engines not only have a large space between the piston pin and the pin hole, but also have a large space between the piston pin and the foot ringconnecting rod (or bearing). the knocking noise is more complicated and may produce a continuous “tacking” sound.
The reason for this failure is that in addition to wear during work that widens the gap, the piston pin, piston pin hole and foot ring connecting rod are made of steel, aluminum and copper during assembly. Their expansion coefficients are very different. If you are a little careless, the gap between the three will become larger due to different thermal expansion during work, causing collisions with each other. In addition, when the gap increases, the axial movement of the piston pin also increases, and the cylindrical end surface of the pin hits the pin ring, adding abnormal sound in the cylinder.
5. Abnormal valve noise
(1) Abnormal exhaust valve leaking noise can be heard from the exhaust pipe muffler.t, such as "squeaking". " sounds when a tire is severely deflated. A valve leak can be heard at the air filter on the top of the carburetor, and the sound resembles the "shh" of a child whistling. The reason is that the working surfaces of the valve and seat are heavily worn or ablated, grooves and stains appear and cannot be tightly sealed. In some cases, the gap between the valve stem and the conduit is too large or. the valve stem is bent, preventing the valve head from being centered and tilted, causing air leakage. If the elastic force of the valve spring is weakened or broken, the valve will not be able to fit tightly. to the working surface of the seat ring, which will also cause air leakage. From the assembly point of view, if the gap between the valve stem and the conduit is too small, it will expand. due to heat during operationnt and get stuck, or if the valve clearance is set too small, the valve stem will be stretched due to heat and the valve will be pushed open by the lifter or rocker arm, which will prevent the valve from closing completely and cause a air leak.
(2) The abnormal noise when the valve spring breaks varies depending on the valve placement method. Once the valve spring is mounted on the broken side, it will make a "click" sound during operation. You can hear it more clearly if you remove the valve cover. After the overhead valve spring breaks, the valve automatically depresses, collides with the piston, and makes a “dang-dang” knocking noise. If it is not extinguished in time, it will cause piston rupture, connecting rod rupture, and even more serious losses.
(3) Too much carbon deposit on the valve will also cause abnormal noise. Because there is too much depositof carbon, the carbon layer will be hot, the piston temperature will be high and the gap between the two. The piston ring groove and piston pin hole will increase, producing a "chatter" sound. This fault is often accompanied by phenomena such as an engine temperature that is too high and an engine that is difficult or even incapable of stalling. The reason is that the proportion of engine oil in the mixed oil exceeds the standard or there is a large amount of engine oil in the oil pan. If it leaks into the combustion chamber , the specific cause must be identified and eliminated.
6. Abnormal noises from the combustion chamber
When the engine load increases, some engines will emit a “click” from the cylinder, which is related The sound during normal operation is different and the Acceleration performance is even worse. This type of abnormal noise is loud and can be heard 5-6 m from the motor. The abnormal noise is especially evident during hard acceleration, which can be taken as a sign of engine knocking. When the combustible mixture burns too quickly in the cylinder, it instantly releases a large amount of heat, causing a sharp increase in pressure in the cylinder. The high pressure gas strongly impacts the top of the piston, cylinder head and cylinder wall, causing knocking. The main reasons for knocking include engine overheating, premature ignition time, excessive carbon deposits in the combustion chamber, low octane rating of gasoline, low calorific value of the spark plug used, etc.