There are many possible reasons for the black smoke failure of diesel engines, but for a diesel engine, the cause of black smoke failure may be only one of the factors. How to judge and confirm the specific cause of black smoke from diesel engine is the key to eliminate this fault. When the cause is found, the fault is eliminated.
1. Confirmation and elimination of the cause of the black smoke failure of the diesel engine caused by fuel supply system problems (1). The fuel supply advance angle is incorrect. The fuel advance angle of the diesel engine is the best advance angle to ensure that the fuel can fully burn after entering the cylinder , Different models have different advance angles.
The fuel injection advance angle is not correct, so that the diesel engine fuel combustion is incomplete and incomplete, which will cause the diesel engine to emit black smoke.
a. The fuel advance angle is too large. If the diesel engine advance angle is too large, the compression pressure and temperature in the cylinder will be relatively low at this time, which will directly affect the combustion performance of the fuel. Severe black smoke. In addition to the large fuel supply advance angle, in addition to the black smoke caused by the diesel engine, there are the following phenomena:
There is a strong burning noise. The power of the diesel engine is insufficient. The fuel consumption is significantly increased. The exhaust pipe interface is wet or dripping
The exhaust temperature may be higher,
The exhaust pipe may be red
B. The fuel supply advance angle is too small
If the fuel supply advance angle of the diesel engine is too small, and the best time is missed when the fuel is injected into the cylinder, it will increase the post-combustion of the diesel engine. If the large amount of fuel is not fully burned, the cylinder will be excluded, and the diesel engine will seriously emit black smoke. In addition to the small fuel advance angle, in addition to the black smoke caused by the diesel engine, there are the following phenomena: the exhaust temperature is high, and the exhaust pipe is red.
The overall temperature of the diesel engine is high, and the diesel engine is overheated due to increased afterburning
Diesel engine power is insufficient.
Fuel consumption increased significantly
Elimination method: If it is confirmed that the black smoke of the diesel engine is caused by the incorrect fuel supply advance angle, as long as the fuel advance angle is adjusted to the design angle, the fault can be eliminated.
(2) Severe wear of fuel injection pump plunger or outlet valve Individual or all severe wear of fuel injection pump plunger or outlet valve will cause the fuel pressure of the fuel injection pump to drop, causing the pressure of the fuel injector (nozzle) to lag relatively, fuel combustion does not Fully, the post-combustion increased, so the diesel engine seriously emits black smoke. The plunger and outlet valve of some cylinders have problems. In addition to causing black smoke from the diesel engine, it will not have a great impact on the use of the diesel engine. However, if most of the plunger and fuel outlet valve of the fuel injection pump are seriously worn, it will cause the diesel engine to emit serious black smoke, and the following phenomena:
Diesel engine is difficult to start. The amount of diesel engine lubricating oil may increase.
Diesel engine power is insufficient. The exhaust temperature of the diesel engine is high, and the exhaust pipe may be red. The diesel engine may be overheated due to increased post-combustion
The basic method to confirm that the black smoke from the diesel engine is caused by the wear of the plunger or the oil outlet valve is:
a. Remove the exhaust pipe of the diesel engine, start the low-speed operation of the diesel engine, carefully observe the smoke exhaust of each exhaust port of the diesel engine, find the cylinder with large smoke exhaust, replace the fuel injector of this cylinder (it can be used with non-black smoke) If the cylinder still emits black smoke and the other cylinder does not emit black smoke, you can confirm that there is a problem with the plunger or fuel outlet valve of the fuel injection pump of the cylinder.
B. Without removing the exhaust pipe, use the single-cylinder fire-fighting method to initially confirm whether there is a problem with the plunger / oil outlet valve or the fuel injector (mouth). The specific methods are:
Start the low-speed operation of the diesel engine, cut off the fuel cylinder by cylinder and observe the change of the smoke at the outlet of the exhaust pipe. If the smoke of the diesel engine decreases after a cylinder is cut off, it means that the fuel supply system of the cylinder Oiler).
Elimination method: When these problems occur during the operation of the diesel engine, the fuel injection pump should be checked. If it is confirmed that the cause of the fault is due to severe wear of the plunger and the outlet valve, this fault can be eliminated after the fuel injection pump is overhauled.
Special note: when overhauling the fuel injection pump, the plunger and the oil outlet valve and related seals should be replaced (completely), check the oil supply angle of each cylinder, and adjust the oil supply amount as required.
(3) Problems with the fuel injector (mouth) a. Poor atomization of the fuel injector, stuck or severe oil dripping. When the fuel injector (mouth) of an individual cylinder is damaged, that is, when the fuel injector (mouth) of a cylinder Poor atomization, seizure, or severe dripping will cause incomplete combustion of the fuel in the cylinder and cause the cylinder to emit black smoke. When there is a problem with the fuel injector (nozzle), in addition to causing black smoke from the diesel engine, the following phenomena are also observed:
The exhaust pipe interface is wet, and in severe cases, diesel may drip. The drip cylinder piston may have a burning top or pull the cylinder failure. The cylinder may have strong combustion noise b. The injection pressure is incorrect. Small) will affect the pressure build-up time of the fuel injector, delay or advance the fuel supply advance angle, and make the diesel engine emit black smoke when working. The injection pressure is too high, which may delay the start of injection and increase the afterburn of the diesel engine. However, the injection pressure is relatively small, and the start of injection may be advanced, and the pre-ignition of the diesel engine will increase. The problems and phenomena generated by the two are similar to the aforementioned incorrect fuel supply advance angle.
The method of confirming whether there is a problem with the injector (mouth) of a cylinder is basically the same as the method of confirming whether there is a problem with the plunger / outlet valve, except that after replacing the injector, the cylinder no longer emits black smoke and the other cylinder Black smoke indicates that there is a problem with the fuel injector (mouth).
Removal method: replace the fuel injection nozzle or fuel injector assembly of the cylinder. When replacing the fuel injection nozzle, you should ensure that it is a similar qualified product and strictly check and adjust the fuel injection pressure according to the requirements, carefully observe the atomization quality of the fuel injector or whether there are problems with low-speed oil dripping, etc., and ensure that the high-quality fuel injector is used mouth).
(4) There is a problem with the fuel injection pump governor. There is a problem with the fuel injection pump governor. The main reason is that the lack of elasticity of the governor speed spring will cause an imbalance between the governor and the throttle control mechanism. Black smoke will be serious. And when the external load changes slightly, the diesel engine is even thicker. If there is a problem with the fuel injection pump governor, the diesel engine still has the following phenomena when running:
The speed of the diesel engine is unstable and may increase or decrease automatically. When running with a load, the speed of the diesel engine decreases seriously as the load increases. The greater the load of the diesel engine, the greater the smoke. When the single-cylinder fire extinguishing method is checked, there is no significant change in the smoke Remedy: professionally repair the fuel injection pump and replace the speed spring or speed governor assembly.
(5) The fuel pump's fuel supply is too large, the fuel pump's fuel supply is too large, it will also cause the diesel engine to emit black smoke, after a large amount of fuel enters the cylinder and is not fully burned, it is excluded from the cylinder. At this time, in addition to black smoke, the diesel engine also has the following phenomena:
The fuel consumption is obviously increased. The exhaust temperature of the diesel engine is too high due to the increased post-combustion and the exhaust pipe may be reddish. Cylinder pulling or piston burning may occur frequently. Remedy: professional maintenance of the fuel injection pump, adjust the injection according to the requirements The oil supply of the oil pump.
Special reminder: When adjusting the fuel supply of the fuel injection pump, the influence of the fuel injection pressure of the diesel fuel injector must be considered, because the fuel quantity is the fuel supply quantity under a specific fuel injection pressure. If the injection pressure changes, the fuel supply will also change accordingly. If the pressure of the standard fuel injector in the fuel injection pump test stand is high, and the actual fuel injector's fuel injection pressure is low, the actual fuel injection volume drop is greater than the adjusted fuel injection volume. On the contrary, it is less than adjusting the injection quantity. The greater the pressure difference, the greater the difference in fuel supply. For example, when the injection pressure of the fuel injector differs by 50 bar, the fuel injection amount may differ by 20%.
