There are many possible causes of diesel engine black smoke fault, but for a diesel engine, the cause of black smoke fault may be only one of them. How to judge and confirm the specific cause of diesel engine black smoke is the key to eliminate the fault. When the cause is found, the fault is eliminated.
1. Confirmation and troubleshooting of the causes of diesel engine black smoke caused by oil supply system problems (1). The oil supply advance angle is incorrect. The oil supply advance angle of diesel engine is the best advance angle to ensure that the fuel can burn fully after entering the cylinder. The advance angle is also different for different models.
Incorrect injection advance angle will lead to insufficient and incomplete fuel combustion of diesel engine, which will lead to black smoke of diesel engine.
a. The fuel supply advance angle is too large. If the fuel supply advance angle of the diesel engine is too large, the compression pressure and temperature in the cylinder are relatively low, which will directly affect the combustion performance of the fuel. The early combustion of the diesel engine increases, the fuel combustion is incomplete, and the diesel engine emits serious black smoke. In addition to the black smoke fault of diesel engine caused by large fuel supply advance angle, the following phenomena also occur:
There is a strong combustion noise. The power of diesel engine is insufficient, the fuel consumption increases obviously, and the interface of exhaust pipe is wet or dripping
The exhaust temperature may be high,
The exhaust pipe may burn 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, the post combustion of the diesel engine will increase, and a large amount of fuel will be discharged from the cylinder before it is fully burned, and the diesel engine will seriously emit black smoke. In addition to the black smoke fault of the diesel engine caused by the small fuel supply advance angle, 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 the increase of aftercombustion
Insufficient power of diesel engine
Fuel consumption increased significantly
Troubleshooting: if it is confirmed that the black smoke of the diesel engine is caused by the wrong oil supply advance angle, the fault can be eliminated as long as the oil supply advance angle is adjusted to the design angle.
(2) The plunger or outlet valve of the fuel injection pump is seriously worn, and the serious wear of individual or all plunger or outlet valves of the fuel injection pump will lead to the decrease of the pump oil pressure of the fuel injection pump, so that the pressure build-up of the fuel injector (nozzle) lags behind, the fuel combustion is insufficient, and the aftercombustion increases, so the diesel engine emits serious black smoke. The plunger and outlet valve of individual cylinders have problems, which will not have a great impact on the use of the diesel engine except for the black smoke of the diesel engine. However, if most of the plungers and outlet valves of the fuel injection pump are seriously worn, the diesel engine will emit black smoke and the following phenomena will occur:
It is difficult to start the diesel engine. The amount of diesel engine lubricating oil may increase
Insufficient diesel power. The exhaust temperature of the diesel engine is high, and the exhaust pipe may burn red. The diesel engine may overheat due to the increase of aftercombustion
The basic method to confirm that the black smoke of diesel engine is caused by the wear of plunger or oil outlet valve is as follows:
a. Remove the exhaust pipe of the diesel engine, start the diesel engine at low speed, carefully observe the smoke exhaust at each exhaust port of the diesel engine, find out the cylinder with large smoke exhaust, and replace the fuel injector of the cylinder (it can be exchanged with the cylinder without black smoke). If the cylinder still emits black smoke and the other cylinder does not emit black smoke, it can be confirmed that there is a problem with the plunger or oil outlet valve of the fuel injection pump of the cylinder.
b. You can also preliminarily confirm whether there is a problem with the plunger / oil outlet valve or fuel injector (nozzle) by using the single cylinder fire extinguishing method without removing the exhaust pipe. The specific methods are as follows:
Start the diesel engine at low speed, cut off the oil 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 the oil is cut off in a cylinder, it indicates that there is a problem in the fuel supply system (plunger / outlet valve or injector) of the cylinder.
Troubleshooting: when these problems occur during the operation of the diesel engine, the fuel injection pump should be checked. If it is confirmed that the fault is caused by serious wear of plunger and outlet valve, the fault can be eliminated after overhauling the fuel injection pump.
Special note: when overhauling the fuel injection pump, replace the plunger, oil outlet valve and relevant gaskets in a complete set (all), check the oil supply angle of each cylinder and adjust the oil supply as required.
(3) Fuel injector (nozzle) problem A. poor atomization, jamming or serious oil dripping of the fuel injector (nozzle). When the fuel injector (nozzle) of an individual cylinder is damaged, that is, when the fuel injector (nozzle) of a cylinder is poor atomization, jamming or serious oil dripping, it will cause incomplete fuel combustion of the cylinder and lead to serious black smoke of the cylinder. When there is a problem with the fuel injector (nozzle), in addition to causing black smoke from the diesel engine, there are the following phenomena:
. the interface of exhaust pipe is wet, and diesel oil may drop in serious cases. The piston of dropping cylinder may have top burning or cylinder pulling failure. The cylinder may have strong combustion noise B, incorrect injection pressure and incorrect injection pressure (too large or too 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 during operation. If the fuel injection pressure is too large, it may delay the fuel injection start time and increase the post combustion of the diesel engine. If the fuel injection pressure is too small, it may advance the fuel injection start time and increase the early combustion of the diesel engine. The problems and phenomena caused by the two are not correct with the fuel supply advance angle mentioned above Indeed similar.
The method of confirming whether there is a problem with the injector (nozzle) of a cylinder is basically the same as that of confirming whether there is a problem with the plunger / outlet valve, except that after exchanging the injectors, the cylinder no longer emits black smoke and the other cylinder emits black smoke, it indicates that there is a problem with the injector (nozzle).
Troubleshooting: replace the fuel injector or fuel injector assembly of the cylinder. When replacing the fuel injector, ensure that it is a similar qualified product, check and adjust the fuel injection pressure in strict accordance with the requirements, carefully observe the atomization quality of the fuel injector or whether there are problems such as low-speed oil dripping, so as to ensure that the fuel injector (nozzle) with high quality is used.
（4） There is a problem with the governor of the fuel injection pump. There is a problem with the governor of the fuel injection pump. The main reason is that when the elastic force of the governor speed regulating spring is insufficient, it will lead to the imbalance between the governor and the throttle control mechanism, and the diesel engine will emit black smoke seriously from the start. When the external load changes slightly, the diesel engine will be full of smoke. If there is a problem with the governor of the fuel injection pump, the diesel engine will run as follows: Like:
. the speed of the diesel engine is unstable and may automatically increase or decrease. When running with load, the speed of the diesel engine decreases seriously with the increase of load. The greater the load of the diesel engine, the greater the smoke. When checking with the single cylinder fire extinguishing method, there is no obvious change in the smoke of the diesel engine. Troubleshooting methods: professionally repair the fuel injection pump and replace the speed regulating spring or governor assembly.
(5) If the fuel supply of the fuel injection pump is too large, the diesel engine will emit black smoke, and a large amount of fuel will be discharged from the cylinder without full combustion after entering the cylinder, which is the increase of post combustion of the diesel engine. At this time, in addition to black smoke, the diesel engine also has the following phenomena:
. the fuel consumption increases obviously. The exhaust temperature of the diesel engine is too high due to the increase of afterburning, and the exhaust pipe may be burned red. Cylinder pulling or piston top burning may often occur. Troubleshooting: professionally repair the fuel injection pump and adjust the fuel supply of the fuel injection pump as required.
Special note: when adjusting the fuel supply quantity of the fuel injection pump, the influence of the fuel injection pressure of the diesel engine injector must be considered, because the fuel supply quantity is the fuel supply quantity under the specific fuel injection pressure. If the fuel injection pressure changes, the fuel supply quantity will also change accordingly. If the pressure of the standard injector of the fuel injection pump test bench is high and the fuel injection pressure of the actual injector is low, the actual fuel injection quantity decreases greatly It is used to adjust the fuel injection quantity. On the contrary, it is less than the adjusted fuel injection quantity. The greater the pressure difference, the greater the difference in fuel supply. For example, when the fuel injection pressure of the injector is 50 bar, the fuel injection quantity may be 20% different.
