Cause analysis and troubleshooting of black smoke in diesel engine 1

Category:Automobile engine repair - Date:2015-11-15

black smoke from diesel engine is one of the most common faults of diesel engine. When we saw the smoke of vehicles running on the highway, our first reaction was that the power of this car was diesel engine. There are many factors that cause the black smoke of diesel engine. The faults of fuel supply system, combustion system, intake and exhaust system may cause the black smoke fault of diesel engine. Based on the actual work experience for many years, the author summarizes the main reasons and elimination methods for the black smoke of a series of air-cooled diesel engines.

Factors affecting the black smoke fault of a diesel engine.

the following factors may cause black smoke in diesel engine.

the problem of.1 oil supply system

(1) the fuel injection advance angle is incorrect: the advance angle is larger or the advance angle is smaller.

(2) the wear of the plunger or outlet valve of the fuel injection pump is serious.

(3) injector (nozzle) problem: nozzle atomization is bad, stuck or dripping oil is serious, or injection pressure is incorrect.

(4) the fuel injection pump governor has problems;

(5) the fuel supply of the injection pump is too large;

2 combustion system problem

(1) the compression pressure of the cylinder is insufficient: the clearance between the piston top is too large, the valve seal is not strict, and the valve seat ring is too deep.

(2) the valve gap is incorrect;

3 air intake system problem

(1) the problem of air filtration quality;

(2) the problem of intake pipe resistance;

(3) the problem of excessive intake temperature;

4 exhaust system problem

(1) the problem of muffler;

(2) the problem of exhaust pipe resistance;

other factors of.5 cause diesel engine to smoke black smoke

(1) the problem of fuel quality;

(2) environmental factors;

(3) the problem of equipment matching;

Two diesel engine black smoke fault reason confirmation and elimination method.

To sum up, there are many possible reasons for the black smoke malfunction of the diesel engine, but for a diesel engine, the cause of the occurrence of black smoke may be only one of the factors. How to identify and confirm the specific cause of black smoke is the key to eliminate the trouble. The reason was found, and the trouble was ruled out.

the confirmation and elimination of the cause of the black smoke fault of the diesel engine caused by the.1 fuel supply system problem.

(1) incorrect advance angle of oil supply

the oil supply advance angle of the diesel engine is the best advance angle to ensure that the fuel can be fully burned after the fuel enters the cylinder, and the model is different and the advance angle is different. Incorrect fuel injection advance angle can cause diesel engine fuel to burn insufficiently and incompletely, which will cause diesel engine to smoke black smoke.

If the oil supply advance angle is large: If the oil supply advance angle of the diesel engine is 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 diesel engine increases, the fuel combustion is incomplete, and the diesel engine is seriously smoked. In addition to the fault of black smoke caused by diesel engine, there are also the following phenomena.

A has a strong burning noise;

The power of B diesel engine is insufficient;

the fuel consumption of C increased significantly.

there is wet or dripping oil on the interface of D exhaust pipe.

E exhaust temperature may be higher, and exhaust pipe may be burning red.

If the oil supply advance angle is small: If the fuel injection advance angle of the diesel engine is small, the best time is missed when the fuel is injected into the cylinder, and the rear combustion of the diesel engine is increased. A large amount of fuel is not fully burned, that is, the cylinder is eliminated, and the diesel engine will take the black smoke seriously. In addition to the failure of diesel engine to smoke black smoke, there are also the following phenomena.

A exhaust temperature is high and exhaust pipe is red.

the overall temperature of B diesel engine is high, and the diesel engine is overheated due to the increase of rear fuel.

The power of C diesel engine is insufficient;

the fuel consumption of D increased significantly.

Elimination method: if the cause of the diesel engine black smoke is due to the misalignment of the oil supply advance angle, the fault can be eliminated as long as the oil supply advance angle is adjusted to the design angle.

(2) serious wear of fuel injection pump plunger or oil outlet valve.

The serious wear and tear of individual or all fuel injection pump plunger or oil discharge valve will result in the drop of oil pressure of the pump pump oil, the relative lag of the fuel injection device (nozzle), insufficient fuel combustion and the increase of post combustion, so the diesel engine is seriously smoked. Some cylinders and plungers and valves have problems. In addition to causing black smoke from diesel engines, they will not have a great impact on the use of diesel engines. But if most of the plunger and oil outlet valves of the fuel injection pump are seriously worn out, causing serious black smoke in the diesel engine, there are also the following phenomena.

A diesel engine is difficult to start. The amount of diesel engine lubricating oil may increase.

The motor power of B diesel is insufficient

C diesel engine exhaust temperature is high, exhaust pipe may burn red.

the D diesel engine may overheat due to the increase of post combustion

It is confirmed that the basic method of the diesel engine black smoke is due to the wear of the plunger or the oil outlet valve: remove the exhaust pipe of the diesel engine, start the diesel engine at low speed, carefully observe the smoke exhaust in each exhaust port of the diesel engine, find out the large exhaust cylinder, and replace the injector of the cylinder (which can be exchanged with the cylinder that does not smoke the black smoke. " If the cylinder is still emitting black smoke and the other cylinder does not smoke black, it can be confirmed that the plunger or oil outlet valve of the fuel injection pump has some problems. It is also possible to remove the exhaust pipe without removing the exhaust pipe, and confirm the problem of the plunger / oil outlet valve or the injector (mouth) by using the single cylinder fire extinguishing method. The specific methods are: starting the diesel engine at low speed, breaking the oil by cylinder and observing the change of the exhaust smoke of the exhaust pipe. If the diesel engine smoke is reduced after a cylinder is broken, the oil supply system (plunger / oil outlet valve or injector) has a problem.

exclude method: when these problems occur during the operation of diesel engine, we should check the fuel injection pump. If the cause of the failure is caused by serious wear of the plunger and oil outlet valve, the trouble can be eliminated after overhaul of the fuel injection pump.

special hint: when the oil pump is overhauled, the plunger and oil valve and the related seal should be replaced, and the oil supply angle of each cylinder is checked and the quantity of oil is adjusted according to the requirement.

(3) the problem of the injector (mouth)

nozzle atomization is bad, stuck or dripping oil is serious. when the injector (mouth) of the individual cylinder is damaged, that is, when the injector (mouth) of the cylinder is not atomized, stuck or dripping seriously, it will cause the incomplete combustion of the cylinder fuel and cause the cylinder to take a serious black smoke. In addition to causing black smoke in diesel engine, there are also the following phenomena when injector (mouth) has problems.

A may be dripped by diesel at the outlet of the exhaust pipe.

B drops of oil cylinder piston may be burned or the top of the cylinder scoring malfunction

C the cylinder may have a strong burning noise

The injection pressure is incorrect: the injection pressure is not correct (large or small), it will affect the pressure time of the injector, delay or advance the oil supply advance angle, so that the diesel engine runs black smoke when working. The injection pressure is too large, which may delay the start time of fuel injection and increase the afterburning of diesel engine. And the injection pressure is too small, which may lead to the early start of fuel injection and the increase of diesel engine early combustion. The two problems and phenomena are similar to those mentioned above. The method of confirming the problem of the injector (mouth) of a cylinder is basically the same as the method to confirm whether the plunger and the oil outlet valve have problems, but after the injector is exchanged, the cylinder is no longer black smoke and the other is black smoke, which indicates that the injector (mouth) has problems.

exclude method: replace the cylinder nozzle or injector assembly. When replacing the nozzle, it should be guaranteed to be a qualified product of the same kind and to check and adjust the injection pressure strictly according to the requirements, carefully observe the atomization quality of the injector or whether there is a low speed drop oil, so as to ensure the use of high quality injector (mouth).

(4) there is a problem in the fuel injection pump governor

There is a problem in the fuel injection pump governor. When the speed of the governor spring is not enough, it will cause the imbalance between the governor and the control mechanism of the throttle, and the diesel engine will take the black smoke seriously from start to start. When the external load changes slightly, the diesel engine is smoky. If there is a problem with the governor of the fuel injection pump, there are the following phenomena in the operation of the diesel engine.

A diesel engine speed is unstable, it may increase or decrease automatically.

when B is running with load, the speed of diesel engine decreases with the increase of load.

the greater the load of the C diesel engine, the greater the smoke.

when D was checked by single cylinder fire extinguishing method, the smoke intensity of diesel engine did not change significantly.

exclude methods: professional maintenance of fuel injection pump, replacement of speed governing spring or governor assembly.

(5) the fuel supply of the injection pump is too large

The fuel supply of the pump is too large, it will also cause the diesel engine to smoke black smoke. A large amount of fuel enters the cylinder and is not fully burned, that is, the cylinder is eliminated. It is the increase of diesel engine afterburning. At the same time, the diesel engine has the following phenomena besides black smoke.

(1) a significant increase in fuel consumption

(2) the exhaust temperature of diesel engine is too high due to the increase of afterburning, and the exhaust pipe may be burned red.

(3) may often appear in the cylinder or piston top burning phenomenon

exclude method: repair fuel injection pump professionally and adjust fuel supply of fuel injection pump as required.

Special hint: when adjusting the fuel supply of the injection pump, the effect of the injection pressure of the diesel fuel injector must be considered, because the oil amount is the amount of oil supply under the specific injection pressure. If the injection pressure changes, the fuel supply will also change accordingly. If the pressure of the standard injector of the fuel injection pump test bench is high, and the injection pressure of the actual injector is low, the actual fuel injection volume is larger than the regulated fuel injection volume. On the other hand, it is less than the adjustment of fuel injection. The greater the pressure difference, the greater the difference of oil supply. For example, when the fuel injection pressure of the fuel injector varies 50 bar, the fuel volume may vary by 20%.

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