What is the reason for black smoke from a diesel engine?
① Underinflation or air leak in the cylinder, poor compression and overload operation
② Fuel supply; The system is not working properly, for example: injector dripping, pressure is low, atomization is poor, fuel injection pump delivers a large amount of fuel, fuel delivery time is too early or too late and the fuel cam is worn.
③The combustion chamber burns and loses its normal function, resulting in poor mixing of fuel and air.
Causes of black smoke when the engine is running
1 Due to poor maintenance, the air filter is clogged and insufficiently inflated, resulting in incomplete combustion.
2. Improper valve clearance adjustment, dirty exhaust and insufficient inflation, and incomplete combustion.
3. Duepoor compression, poor mixing and incomplete combustion.
4. The fuel supply advance angle is incorrect, or the injection quality is poor, the mixture is not good, and the combustion is incomplete.
5. The exhaust pipe and muffler are clogged, and the exhaust is not properly inflated and combustion is incomplete.
6. Due to slight combustion or cylinder sticking, the internal load of the engine is too large, or the engine has been overloaded for a long time, the mixture is too rich, there is not enough oxygen and combustion is incomplete.
The diesel engine emits black smoke
1. The main causes of black smoke emission from diesel engine are:
(1) The intake air temperature is too high.
(2) The air filter is too dirty or the air intake pipe is blocked.
(3) The fuel injection nozzledrip or has poor atomization.
(4) There is a problem with the fuel injection pump.
(5) The injection advance angle is incorrect.
(6) Valve clearance is incorrect.
(7) The cylinder is seriously worn.
(8) There is a problem with the compressor.
2. Troubleshooting Methods
Check it carefully and handle it appropriately.
The following will analyze the abnormal smoke emissions of diesel vehicles and provide corresponding solutions.
1. Diesel vehicle emitting black smoke
Diesel is a complex hydrocarbon injected into the combustion chamber decomposes at high temperature to form black carbon, which is accompanied by the exhaust gas. gas when exhausted. They are discharged together to form black smoke. Black smoke emitted by diesel vehicles is the most common fault phenomenon during smoke analysis and diagnosisblack emitted by diesel vehicles, it should be treated according to the specific situation.
Phenomenon 1: After the diesel vehicle turns on the starter, the exhaust pipe emits a large amount of black smoke, but the engine cannot start.
This phenomenon occurs before the engine operates normally. There are many reasons why the engine cannot run, mainly in the fuel system and air intake system. The diesel engine is not easy to start, which means that although diesel enters the combustion chamber, for some reason the combustion chamber does not have compression ignition conditions, so that the injected diesel cannot burn or cannot be completely burned.
Common causes of faults and analysis
★ The fixing bolts of the fuel injection pump drive coupling soundt loose or the fuel injection timing is set too early.
★ The fuel injection pump is defective, that is, the piston, tappet or cam of the fuel injection pump is seriously worn, or the screw piston lifter adjustment knob is loose.
★ Fuel injector failure, i.e. the fuel injector needle is sticky and cannot be closed, the needle and valve seat are in poor contact or leaking and the injection pressure spring adjustment screw is loose.
★ When the piston pair of the fuel injection pump is worn, the regulator is incorrectly adjusted and the fuel supply volume is too large.
★ Cylinder pressure is too low.
★ The air filter or air intake passage is clogged.
Fault Diagnosis
First check whether the inlet and exhaust passages are unobstructed,for example if the air filter is blocked, if the air intake pipe is dented, etc.
If the engine makes a knocking noise and emits black smoke, this means that the injection time is too early and the injection timing must be readjusted. This condition is usually caused by a loose fuel injection pump coupling screw, a damaged shaft key, or misalignment of the driven disc. If no problem is found, you can check the injection timing as follows: remove the high pressure oil pipe from the first cylinder, so that the oil level in the center hole of the support seat of the oil outlet valve of the injection system is clearly visible, and position the oil supply rack. In the oil supply position, pump air from the oil circuit from the bleeder plug, slowly rotate the crankshaft and carefully observe the changeslevel of the oil outlet valve of the oil pump. As long as the fluid level changes, it means the oil supply has started. Immediately stop the crankshaft and check whether the injection advance angle is correct. At this time, the distribution line of the fuel injection pump connection plate should coincide with the line engraved on the pump body.
If the above checks are normal, you can check the atomization status of the injector. When the injector is tested on the test bench, the injection pressure, angle and range of the injection cone must comply with the standards, otherwise the needle valve must be dismantled and inspected. Check whether the needle is stuck, whether the needle and seat are sealed, whether the injection pressure adjustment spring is too soft or broken, whether there is carbon deposits on the seat hole seal injector, etc.
If Ali's systemOil supply is normal and the engine emits black smoke and cannot start, the engine cylinder pressure should be checked. If the pressure is insufficient, the cause must be sought at the valve, piston and cylinder seal.
Phenomenon 2: The engine runs unevenly and emits a large amount of black smoke.
If the engine can run, it means that the fuel has entered the cylinder and started working. However, the operating conditions are not very stable. The phenomenon of a large amount of black smoke emitted by the engine. also reflects this problem. The fault at this stage is mainly caused by the fuel injection system. Of course, low cylinder pressure can also cause such defects.
Common causes and fault analysis
★ Fuel injection pump failure, i.e. excessive wear of individual camslles or oil pump lifter rollers, incorrect adjustment or loosening of lifter adjustment screws, and individual plunger sleeves Sector gear mounting screws are loose, individual plungers are stuck or springs are broken, the oil discharge valve is worn or springs are broken, etc.
★ Fuel injector failure, that is, the fuel injector needle is stuck and cannot be closed, the fuel injector needle is poorly sealed, the pressure adjustment spring of the fuel injector is broken or the elasticity is too low, the fuel injector settles on the seal, etc.
★ The pressure in the cylinder is too low, for example the piston ring is leaking or the cylinder seal is not tight.
Troubleshooting
First, check the working condition of the motor. You can try performing an oil cut testcylinder by cylinder while the engine is running. When a cylinder cuts off oil, if the engine speed decreases significantly, the black smoke will decrease and the knocking noise will become quieter or disappear, it means that the fuel supply to the cylinder is too low; if there is no change in the engine or the change is very small, it means that the fuel supply to the cylinder is insufficient if the engine speed changes little; and the black smoke disappears, it means the spray quality of the injector of this cylinder is poor. After finding the faulty single cylinder, further check the cause of the fault, such as the condition of the cylinder fuel injection pump piston pair, whether the sector gear fixing screw is loose and whether the piston spring is broken, etc. . If it is normal, the injector can be disassembled and inspected. If necessary, a new injector can be installedfor comparison ; If the fault disappears when using the new injector, it means the original injector is defective.
If the fuel injection volume of each cylinder is too large, open the regulator cover and check whether the adjustment rod scale moves too much in the injection pump housing of fuel (the scale line should be equal to the rear end surface of the fuel injection pump housing). If the diesel engine emits black smoke and you hear sharp knocking in the cylinder, this means that the injection time is too early and the injection timing must be correctly calibrated. If the air filter is found to be clogged (the filter element is dirty) upon inspection, it should be cleaned and blown immediately.
Secondly, if the fuel injection pump piston lifter has an adjustment screw, check whether the fuel injection timingon of each cylinder is coherent.
If there are no problems with the above items, a pressure test can be performed on the faulty single cylinder to determine if the fault is caused by wear and leakage of the cylinder, piston, piston ring, etc. or poor valve sealing.
Other maintenance items for engine black smoke emission
In addition to the reasons for black smoke emission from the fuel system, it is also necessary to watch out for incomplete combustion due to insufficient air intake. After observing whether the air filter element is blocked and the air intake pipe is leaking, you should also pay attention to whether the exhaust pipe is blocked or the back pressure is too high, causing insufficient air intake and thus affecting the air-fuel ratio. . After solving the above faults, you should check whether the jIf the valves are correctly adjusted, the sealing performance of the valve and seat, and whether the valve spring works normally, etc. The diesel used in some engines is of poor quality or brand, which can also cause black smoke from the exhaust. The appropriate diesel should be selected according to the model, structure and temperature difference conditions, and should be used in strict accordance with. the manufacturer's instructions.
2. Diesel Vehicle Blue Smoke Failure
When it comes to blue exhaust smoke, we will think of the blue smoke emission failure that often occurs in gasoline vehicles. In this fault, the blue smoke emitted by both types of combustion engines is usually caused by lubricating oil escaping into the combustion chamber and being burned. Therefore, it is recommended to carry out inspections onivantes after discovering blue smoke:
★ Check if the oil level in the oil pan is excessive. As the crankshaft rotates at high speed, oil splashes against the cylinder wall and escapes into the combustion chamber. It should be noted that when checking the oil level is too high, you should not remove the oil dipstick to check immediately after stopping the engine, because the lubricating oil splashed on the crankcase wall will not It has not yet flowed back, so you must stop the engine for 10 minutes before removing the oil dipstick.
★ Check the condition of the cylinder liners, pistons and piston rings. If the wear is large and the gap is too large, causing oil leakage outside the combustion chamber for combustion, and accompanied by an increase in engine crankcase exhaust gas, the worn piston should be replaced in time. The piston ring loses its function and alarge amount of engine oil flows to the combustion chamber for combustion, resulting in blue smoke being emitted, the piston rings should be removed, carbon deposits should be removed, each piston ring should be assembled correctly and piston rings should be replaced if necessary. For new or just serviced cars, lubricating oil will generally not leak due to excessive clearance between the piston and cylinder. It is often the inner and outer notches (or corners) of the piston ring that cause lubricating oil to leak, so you need to be careful to check.
★ The gap between the valve and the valve guide is too large, and a large amount of engine oil is drawn into the combustion chamber for combustion. The worn valve and valve guide must be replaced. For a turbocharged engine, if there is burning oil and exhaust smokeblue appearance, but the engine power does not decrease and organic oil stains can be seen adhering to the compressed air outlet or on the intake pipe, it can essentially be determined that it is 'a turbocharged engine. a turbine. The compressor is leaking oil. Engine oil enters the combustion chamber with the air flow and is burned. At this time, the compressor must be replaced. The lubricating oil should also be checked for contamination and replaced if necessary.
★ Check if the air filter is clogged. A clogged air filter will increase the resistance during the cylinder air intake process and make the air intake irregular. There is some negative pressure in the cylinder, which also draws lubricating oil into the combustion chamber. Therefore, when blue smoke appears, the filter should also be checked and cleaned.
3. Echa broadcastdiesel vehicle operation in case of white smoke
The fuel contains water or cooling water escapes into the cylinder, and after being heated, it turns into steam and is ejected from the exhaust pipe. This often causes white smoke. The injection time of the diesel engine is too late, the injection pressure is low, and poor atomization may cause the diesel to be released into white smoke without being completely burned. It should be noted that when cold starting in winter, a large amount of white smoke is emitted from the exhaust pipe, but the white smoke gradually disappears after a period of operation, which is normal.
Common causes and fault analysis
★ The motor temperature is too low. Some diesel fuel turns into oil vapor before burning and is exhausted from the tailpipe with the exhaust gases, emitting white smoke.
★ There is water in the oil supply system. There is water in the fuel or combustion chamber. The water is heated to water vapor by the heat given off by combustion in the cylinder and is exhausted from the exhaust pipe to form white smoke.
★ Fuel injection time is too late. Due to the late fuel injection time, the cylinder temperature dropped during fuel injection, and some of the unburned diesel fuel turns into oil vapor and white smoke is emitted.
★ The fuel injector has poor atomization. Poor atomization results in incomplete combustion of diesel fuel, resulting in white smoke.
★ Cylinder pressure is too low. Some diesel fuel turns into oil vapor without being burned, so white smoke comes from the exhaust.
Troubleshooting and troubleshooting
The diesel engine emits white smoke when first started and turns into black smoke as the temperature increases. This shows that the pressure in the cylinders is insufficient. Although this pressure can keep the diesel engine cranking, due to the low temperature during startup, some of the diesel evaporates into vapor before being burned. Check valve seal for tightness, valve timing, cylinder seal or injection seat hole seal for leaking, excessive cylinder wear, stuck piston ring, or its openings overlap, etc.
The diesel engine runs weakly and emits white smoke. You can put your hand near the exhaust pipe. When white smoke passes and there are water droplets on your hand, it means that water has entered the cylinder. At this time, you can use the mo oil cutting methodnocylinder to find it. the leaking cylinder. If the speed of diesel engine is affected when only one cylinder is cut off, please explain The cylinder is working well, otherwise it means the cylinder is not working. You need to remove the injector and check if there is any trace of water on the injection hole. If water is found, check the cause of water infiltration and find out. whether it is a broken cylinder or a washed cylinder seal; if the cylinder is in the same condition and still not working and emitting white smoke, you need to check if there is water in the diesel. At this point, you can open the fuel tank and fuel filter drain plugs to check if there is water in the fuel.
When the diesel engine runs at high speed, the work is uneven, the acceleration is unresponsive, the temperature is too high, the work is low, and the exhaust pipe emits smoke gris-white. This means that the fuel injection time is too late. You must check and adjust the tightness of the connection plate mounting screws as well as the keys and grooves. Slowly advance the fuel injection time so that the white smoke is cleared and the engine runs normally. there is still no improvement after adjustment, you should check whether the timing adjustment screw of each cylinder piston of the fuel injection pump is unbalanced and take action.
When the diesel engine emits white smoke, the engine operating temperature may be increased. If the color of the exhaust changes from white smoke to black smoke when the water temperature is around 70°C, it can be judged. This is due to poor atomization of the injector. Use the cylinder-by-cylinder oil cut-off method to discover the faulty injector, then checkthe injector; if there is oil dripping during injection, also check whether it is caused by low injection pressure or deformation of the needle valve body or even caused by excessive wear, improving Thus.
Troubleshooting:
According to convention, it is generally believed that the Cummins diesel generator oil system is caused by air, blockage or loose seal, but when This is the specific For diesel generators, maintenance personnel should first check the oil system, filter elements and other related components, and find no leaks or blockages in the engine; check fuel pump, fuel injectors, etc. and find no problem further; Valve clearance, injection advance angle, etc. of the diesel generator were checked and adjusted, but the fault still existed.
Analysis of the causes of failure:
Then, the technical staff analyzed that thegenerator check valve was not damaged, but only a little dust or dust particles adhered to the one-way engine oil return valve. The steel ball and sealing belt of the valve are on the upper surface, which prevents the valve from closing tightly, which will cause the generator set to fail in operation. It sounds simple, but it took several days from when the problem occurred to when it was resolved. Actually, I first suspected that there was something wrong with the oil return bolt, but when I pumped oil with a manual oil pump, I felt that the pressure in the oil system was basically normal, and there was also clear oil return. noise coming from single oil return bolt.