Common failure phenomena and solutions of diesel generators
Common failure phenomena and solutions of diesel generators
In the process of using the diesel generator set, there will be some failure phenomena. What is the solution? Reed Power, a professional manufacturer of diesel generators, will give you an explanation: The prerequisite for the normal operation of a diesel engine is that the atomized diesel can be accurately and timely injected into the combustion chamber, and the compressed air in the combustion chamber must reach a sufficient temperature to catch fire. break out. To meet these two conditions, it is necessary to have a sufficiently high speed and a certain temperature in the cylinder when the diesel engine is started. When the diesel engine cannot be started, the cause should be found from the aspects of starting work, diesel fuel supply system and compression.
(1) The ambient temperature is too low. In the case of low temperature, the diesel engine should be preheated, otherwise it will not be easy to start.
(2) The starting speed is low. For a crank-started diesel engine, the speed should be gradually increased, and then the decompression handle should be moved to the non-decompression position, so that the cylinder has normal compression. If the pressure reducing mechanism is not adjusted properly or the valve is against the piston, it will often feel difficult to shake the car. Its characteristic is that the crankshaft can't move when it turns to a certain position, but can return. At this time, in addition to checking the decompression mechanism, you should also check whether the timing gear meshing relationship is wrong. For diesel engines that use electric starting, if the starting speed is extremely slow, most of the starters are weak, which does not mean that the diesel engine itself is faulty. The electrical circuit should be inspected in detail to determine whether the battery is fully charged, whether the wires are tightly connected, and the starter is working properly.
Judging the technical status of the engine from the color of the engine exhaust
When the engine is operating, the fuel is burned in the cylinder to generate exhaust gas and discharged outside the engine. When the engine is operating normally and the fuel is completely burned, the exhaust gas mainly contains water vapor (H2O), carbon dioxide (CO2) and nitrogen (N2). The exhaust gas is generally light gray. When the fuel is incompletely burned or the engine is not working properly, harmful substances such as hydrocarbons (HC), carbon monoxide (CO), nitrogen oxides (NOx) and carbon particles will be present in the exhaust gas, making the color of the exhaust gas white, Black or blue. It can be seen that the color of the engine exhaust can reflect the fuel combustion status and the technical status of the engine. Therefore, car drivers and car maintenance personnel can judge the technical status of the engine by the color of the engine exhaust.
First, exhaust smoke
The black smoke in the exhaust gas is mainly carbon particles with incomplete combustion of the fuel. Therefore, the excessive supply of fuel in the fuel supply system reduces the amount of air in the intake system, the poor sealing of the combustion chamber formed by the cylinder block, cylinder head, and piston, and the poor injection quality of the fuel injector will cause incomplete combustion of the fuel, which will cause exhaust. Black smoke. The black smoke from the exhaust is mainly due to the following reasons:
1. The oil supply of the high-pressure oil pump is too large or the oil supply of each cylinder is uneven
2. Insufficient valve seals cause air leakage and low cylinder compression pressure
3． Air filter blockage, large intake resistance, insufficient air intake
4． Heavy wear on cylinder liners, pistons, and piston rings
5. Injector does not work
6. Engine overload
7. The fuel injection advance angle of the injection pump is too small, and it is moved to the exhaust process after the combustion process.
8. Control failure of gasoline EFI system, etc.
For smoky engines, it can be checked and eliminated through high-pressure oil pump adjustment, injector injection test inspection, cylinder compression pressure measurement, intake port cleaning, adjustment of fuel supply advance angle, and gasoline EFI system fault diagnosis.
Second, the exhaust emits white smoke
The white smoke in the exhaust is mainly fuel particles or water vapor that are not sufficiently atomized and burned. Therefore, any failure to atomize the fuel or water entering the cylinder will cause the exhaust to emit white smoke. The main reasons are summarized as follows:
1. Low air temperature and insufficient cylinder pressure, poor fuel atomization, especially the white smoke from the exhaust during the initial cold start
2. Cylinder gasket damaged, cooling water seeps into the cylinder
3． Cylinder block cracked, cooling water penetrated into the cylinder
4． Large water content in fuel, etc.
The exhaust emits white smoke during a cold start. It should be considered normal if the white smoke disappears after the engine is warmed up. If the vehicle still emits white smoke during normal operation, it is a failure. You should observe whether the cooling water in the water tank is consumed normally and whether each cylinder works Normal, check if there is too much water in the oil-water separator, etc.
Third, the exhaust emits blue smoke
The blue smoke in the exhaust is mainly the result of excessive oil penetrating into the combustion chamber to participate in the combustion. Therefore, whatever causes the oil to penetrate into the combustion chamber will cause the exhaust gas to emit blue smoke. The main reasons are summarized as follows:
1. Broken piston ring
2. The oil return hole on the oil ring is blocked by carbon deposits and loses the oil scraping effect.
3． Piston ring openings turn together, causing oil to escape from piston ring openings
4． The piston ring is severely worn or stuck in the ring groove by carbon deposits and loses the sealing effect
5. Install the air ring upside down, scrape the oil into the cylinder and burn it
6. Insufficient elasticity of piston ring and unqualified quality
7. Improper valve duct oil package or aging failure, loss of sealing effect
8. Heavy wear on pistons and cylinders
9. Too much oil is added, so that the oil splashes too much, and the oil ring is too late to scrape the excess oil from the cylinder wall.
Exhaust blue smoke will inevitably be accompanied by increased consumption of oil, and some drivers call it "burning engine oil." The oil and fuel consumption ratio is generally 0.5% to 0.8%, the oil consumption
When this value is exceeded, blue smoke will be generated in the exhaust. Engine blue smoke failure, usually through the engine disassembly, inspection, in order to find out the cause and determine the troubleshooting plan. In the cold state, the exhaust smoke is blue, but if the oil consumption is normal, it is related to the fuel and is considered normal.
Engine exhaust should generally be checked when the engine is warmed up, and analyzed through changes in the exhaust smoke color during low, medium, high, and acceleration of the engine
After using the generator for a period of time, it is found that everything else is normal but the power is reduced. What is the main reason?
a. The air filter is too dirty and the intake air is not enough. At this time, the air filter must be cleaned or replaced.
b. The fuel filter is too dirty, and the fuel injection volume is not enough. It must be replaced or cleaned.
c. The ignition time is not correct and must be adjusted.
The abnormal noise in the engine cylinder can be summarized as the sound of piston knocking, the sound of piston pin knocking, the sound of piston crown hitting the cylinder head, and the piston striking
Knock sound, piston ring knock sound, valve knock sound and cylinder knock sound
1.The impact sound of piston top and cylinder head
The abnormal sound of the piston crown hitting the cylinder head is a continuous metal tapping sound, especially at high speeds. The abnormal sound source is in the upper part of the cylinder, its sound is solid and powerful, and the cylinder head is vibrated. The main reasons are as follows.
(1) The crankshaft bearings, connecting rod bearings, and piston pin holes are severely worn, and the clearance is severely exceeded. At the moment of the piston stroke change, the piston hits the cylinder head on the top under the effect of inertia.
(2) The distance between the center line of the piston pin hole and the top surface of the piston is larger than the original piston due to the misinstallation of other similar specifications or fake products when the piston is replaced. .
If you encounter such a situation during driving, the first aid is to remove the cylinder head and add a cylinder pad to raise the cylinder head without collision. However, when repair conditions are available, repairs should be carried out immediately to restore their good technical condition.
2.The abnormal sound of the piston ring
The abnormal sounds at the piston ring mainly include the metal knocking sound of the piston ring, the air leakage sound of the piston ring and the abnormal sound caused by excessive carbon deposits.
(1) The metal rattle of the piston ring. After the engine has been working for a long time, the cylinder wall is worn, but the upper part of the cylinder wall can not be kept in contact with the piston ring. The original geometry and dimensions are almost maintained, which creates a step on the cylinder wall. If the old cylinder pad or the new one is too thin, the piston ring at work will collide with the cylinder wall step, and a dull “噗噗” metal impact sound will be emitted. 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 large knocking sound.
(2) Leak sound of piston ring. The elasticity of the piston ring is weakened, the gap of the opening is too large or the openings overlap, and the groove on the cylinder wall will cause the piston ring to leak air. The sound is a "drink" or "hissing" sound, and a "snoring" sound is emitted when there is a serious leak. The diagnostic method is to turn off the engine when the water temperature of the engine reaches above 80 ° C. At this time, you can inject a little fresh and clean engine oil into the cylinder, restart the engine after cranking the crankshaft for a few revolutions, and if the abnormal noise disappears at this time, but soon again If it appears, it can be concluded that the piston ring is leaking.
(3) Abnormal sound of excessive carbon deposits. When the carbon deposits are excessive, the abnormal noise emitted from the cylinder is a sharp sound. Because the carbon deposits are burned red, the engine has the symptoms of premature ignition, and it is difficult to stop the flame. The formation of carbon deposits in the piston ring is mainly due to the tight seal between the piston ring and the cylinder wall, the gap between the opening is too large, the piston ring is reversely installed, and the ring ports are overlapped. The burning of the ring part causes the formation of carbon deposits and even sticks to the piston ring, so that the piston ring loses its elasticity and sealing effect. After replacing the piston ring with proper specifications, this fault can be eliminated.
Cylinder knock refers to the "dangdang" or "click" of the piston at the moment when the piston starts working, or when the piston moves upward, the piston swings in the cylinder, and its head and skirt collide with the cylinder wall. Unusual sound. If it is a "dangdang" sound, it is mostly caused by poor lubrication of the cylinder wall. At this time, a little oil can be dripped into the cylinder, and then the engine is started. If the abnormal noise is reduced or disappeared, the abnormal noise is indeed caused by poor lubrication. If it is a "click" sound and the blue smoke is emitted from the exhaust pipe at the same time, it is generally due to the excessive gap between the piston and the cylinder wall. The main reasons for the above situation are as follows:
(1) If this phenomenon occurs only after the cold car is started. When the water reaches normal water temperature, it disappears on its own, because the gap between the piston and the cylinder wall is too large, and the piston shrinks when the car is cold, which further increases the gap between the two, resulting in obvious knocking. After the machine temperature rises, the piston expands and the gap tends to a normal value, so the abnormal noise disappears. This situation will not cause major problems in the short term.
(2) The engine oil grade does not meet the requirements. When the engine is restarted after a long period of flameout, the engine oil is viscous and poor in fluidity. A good oil film cannot be formed on the cylinder wall in a short time. The piston and the cylinder wall directly collide to cause knocking. After running for a period of time, the viscosity of the lubricating oil is normal, a layer of oil film is formed on the cylinder wall, and the abnormal noise is weakened or disappeared. As long as the lubricant is selected reasonably, and the crankcase of the engine is warmed up before starting, and lubricated with mixed oil, step on the starting lever several times before starting to make the parts adhere to more lubricant. In this case, avoid.
(3) The mixture entering the cylinder cannot be burned normally, causing pre-ignition or deflagration, or the moment when the engine is under no load and the accelerator is suddenly applied, the sound of the piston colliding with the cylinder wall will be generated. The engine should be maintained at normal temperature, use gasoline that meets the requirements of octane number, and adjust the ignition timing appropriately.
(4) The piston skirt is worn and the cylinder error is too large. When the piston moves upwards, the top of the piston will hit the cylinder wall, and the piston and the cylinder are seriously worn. The gap between the two? ? wall. After disassembly, check and take corresponding repair measures according to the situation.
(5) Due to the torsion of the connecting rod, the piston pin is deviated from the pin hole, and the two axis lines of the crank pin and the piston pin are not parallel, etc., which will also cause the piston to run deflection in the cylinder and hit the cylinder wall. This situation can only be checked after disassembly, and the corresponding parts should be replaced after diagnosis.
4.The knocking sound of the piston pin
If the gap between the piston pin and the piston pin hole, the piston pin and the connecting rod small head bushing (or bearing) is too large, a sharp, crisp, high-pitched "click" metal percussion sound will be emitted. The sound of a small hand hammer striking the iron drill. The rule is that the engine does not sound when the cold car starts, and it sounds when the temperature increases, and the higher the temperature, the louder. If the ignition time is adjusted forward, the sound will speed up and increase. If the spark plug is cut off, the sound will weaken or disappear.
Some engines not only have a large gap between the piston pin and the pin hole, but also a large gap between the piston pin and the connecting rod small head bushing (or bearing). In this case, the knocking sound is more complicated, and a continuous "click" sound will appear. .
The reason for this failure is that in addition to wear during work, the gap becomes larger. During assembly, the piston pin, the piston pin hole, and the connecting rod small head bushing are made of steel, aluminum, and copper. The expansion coefficients are very different. Slightly sloppy, the gap between the three during work will be enlarged due to different thermal expansion, causing collisions with each other. In addition, when the clearance increases, the amount of axial movement of the piston pin also increases, and the cylindrical end face of the pin will hit the pin ring, which increases a kind of abnormal noise in the cylinder.
5, the abnormal sound of the valve
(1) The abnormal noise of the exhaust valve can be heard at the muffler of the exhaust pipe, such as the "squeak" sound when the tire is leaking seriously. Leakage of the valve can be heard at the upper air filter of the carburetor, and its sound is like a "hush" sound when the child whistles. The reason is that the working surfaces of the valve and the seat ring are severely worn or ablated, and grooves and spots appear, which cannot be closed tightly. Some are because the gap between the valve stem and the catheter is too large or the valve stem is bent, so that the valve head cannot be centered and skewed, causing air leakage. If the spring force of the valve spring is weakened or broken, the valve cannot fit tightly with the working surface of the seat ring, which will also cause air leakage. In terms of assembly, if the gap between the valve stem and the duct is too small, it will be stuck due to thermal expansion during work, or the valve gap is adjusted too small, and the valve stem is heated and extended, and the valve is opened by the lifter or rocker. Will make the valve can not be completely closed and leak.
(2) The abnormal sound when the valve spring is broken depends on the valve placement method. After the side-mounted valve spring is broken, a “beep” sound is emitted during work. If the valve cover is removed, the sound will be clearer. After the overhead valve spring is broken, the valve automatically sinks, and it will collide with the piston, and a "dangdang" knocking sound will appear. If the latter does not turn off in time, it will cause the piston to rot, break the connecting rod, and even more serious losses.
(3) Excessive carbon deposits in the valve can also cause abnormal sounds. Because of excessive carbon deposits, the carbon layer is hot, the temperature of the piston is high, and the gap between the piston ring groove and the piston pin hole is increased. Abnormal sound. This failure is often accompanied by phenomena such as excessive organic temperature, difficulty in stopping the engine or failure to stop the engine. The reason is that the proportion of engine oil in the mixed oil exceeds the standard or a large amount of oil from the sump enters the combustion chamber, and the specific cause should be further investigated and eliminated.
6, abnormal sound from the combustion chamber
When the engine load increases, some engines emit a "click" sound from the cylinder, which is different from the sound during normal operation, and even accompanied by deterioration in acceleration performance. This abnormal sound volume is large, can be heard at 5-6m away from the engine, the abnormal noise is particularly obvious during sudden acceleration, which can be regarded as a sign of engine knock. When the combustible mixture burns too fast in the cylinder, it instantly releases a large amount of heat, causing the pressure in the cylinder to rise sharply, and the high-pressure gas strongly impacts the piston crown, the cylinder head and the cylinder wall, causing knocking. The main reasons for knocking are overheating of the engine, premature ignition time, excessive carbon deposits in the combustion chamber, too low octane number of gasoline, low spark plug heating value, which does not meet the requirements.