1. phenomenon

The diesel engine is not easy to start, or the speed is not easy to improve after starting.

2. reasons analysis

In addition to overcoming the friction resistance of each part of the engine and driving all the auxiliary devices (such as the Baotou North run heavy card accessories pump, the injection pump, the fan, the air compressor, the generator, the oil pump and so on), the power of the fuel in the engine cylinder is finally passed out by the flywheel. If the heat in the engine cylinder is small or the heat efficiency is not high, the friction resistance of the engine is too large or the power of each auxiliary device is driven to increase, the engine output power will be reduced and the engine is weak. The reasons for the above phenomena are as follows:

(L) the impact of the failure of the fuel supply system

Insufficient oil supply

The fuel system should be able to timely and properly spray atomized fuel into the cylinder. If the fuel system fails and the oil in the cylinder is less, the heat generated by the combustion is reduced, and the engine is weak when the heat is reduced to the engine's load.

Poor spray mass

When the engine is working, the spray quality of the injector is poor, the fuel surface area of the ejector cylinder is small and the oxygen binding rate is reduced. Even if the quantity of oil in the cylinder is quite a few, the heat of the atomization is less and the heat is less because of the poor atomization quality.

The effect of injection advance angle

The amount of fuel in the cylinder should be suitable. If the pressure rise rate of fuel during the fast and tender period increases, it will easily cause the engine to work rough. Rough work will consume part of the power, that is, the utilization of thermal efficiency is not high, the effective output of external output will be reduced. The fuel injection advance angle is too small, and the combustion process is mostly moved to the expansion and work process. The pressure rise rate decreases, the maximum pressure drops, the exhaust temperature increases, the heat loss of the cooling water is much, and the thermal efficiency decreases significantly.

The effect of inflating volume

The fuel can be burned in the cylinder, mainly the result of the chemical reaction of carbon atoms in the diesel and oxygen atoms (producing carbon dioxide) to release the heat. If the air filter is blocked by the Baotou North running heavy card accessories air filter, the cross section of the air is reduced (the turbocharger with a turbocharger has a miasma. " Reduced) or the influence of the gas distribution mechanism causes the engine to be inadequately inflated, causing the carbon atoms in the fuel to not fully react with the oxygen atom, so the heat of the release is reduced and the engine is weak.

Bad sealing of machine parts containing working medium

If the cylinder mats are broken, the valve is closed, the gap between the piston and the cylinder wall is too large, the air leakage can be caused by the bad compression, and the combustion effect of the fuel in the cylinder is not good and the engine is weak.

The influence of environmental temperature

When the ambient temperature is too high, it often causes the engine to overheat. Under the dual action of high ambient temperature and engine overheating, the air expands, thus affecting the aeration volume of the engine and reducing the power of the engine. When the ambient temperature is too low, it will cause the evaporation of fuel in the cylinder is bad, resulting in incomplete combustion, that is, the heat generated by the working medium in the cylinder will be reduced.

(2) the influence of engine resistance

If the engine assembly is too tight and the oil is too thick, the engine resistance will be too high. In addition to overcoming the friction force of the engine and the resistance of the auxiliary device, the power generated by the engine reduces the effective power of the output, that is, the engine is powerless.

3, diagnosis and elimination

Diagnosis is made according to the cause of the analysis and the phenomenon of failure.

(1) if the exhaust is less and not easy to start at the start of the engine, the reason is that the fuel supply system is deficient in oil supply and should be diagnosed and eliminated according to the fault described in the fuel system.

(2) if the engine starts to start smoothly, the exhaust pipe is smoked, and the engine speed is not easy to improve. The main reason is that the air in the cylinder is too small. The air filter of the intake part should be checked (with the turbocharger engine to check the turbocharger) and be excluded.

(3) if the engine overheating occurs, most of them are caused by the late injection time, which is the reason for the inability of the engine to be adjusted and should be adjusted. The adjustment method can be seen in the narrative part that the engine can not start.

(4) if the exhaust pipe of the engine has blue and white smoke, it indicates that the engine's inability is caused by air blow in the cylinder and should be treated.

(5) inspection of air leakage

To move the engine flywheel to make the piston of the inspected cylinder compress to the stop point, remove the injector, hang the low speed gear and pull the hand brake, and then use the hose to fill the air with the air from the nozzle hole to the combustion chamber, then another person is leaking at the inlet pipe or exhaust pipe, the oil filling port, the cylinder pad, or the radiator filling port. Sound. If a leak is heard somewhere, it indicates that the cylinder is poorly sealed. For example, the air leakage is heard in the exhaust pipe or inlet pipe, indicating that the gas is closed, or the air leakage is heard in the water inlet of the heavy card accessories radiator in the north of Baotou, indicating that the cylinder pad is damaged. After ascertainment, it should be excluded.

(6) check engine resistance

Use the crowbar to pry the engine flywheel. If the feel is more difficult than the other type diesel engines or more normal use, it shows that the resistance of the diesel engine is too large. If the newly repaired diesel engine is mostly caused by too tight assembly, it should be run in or reassemble.

(7) check the phase of gas distribution

If the above inspection is normal, then the diesel engine may be unable to cause the gas distribution phase, and then check the valve clearance of the valve and the crankshaft angle when the inlet and outlet door open or close, and then it can be found out with the matching map.Valve timing check method: valve clearance adjustment should meet the specified value of technical documents. Open the engine flywheel shell to observe the window cover, and use the crowbar to move the flywheel to make the first cylinder piston compress to the stop point, make a 3 fertilizer dial and pointer, and fix the dial on the pulley, the pointer is fixed on the front cover plate to point the pointer to the "J" of the dial. The valve chamber cover is removed, the dial and the frame are placed on the cylinder head to detect the rotation of the flywheel, and the push rod of the valve will be rotated by hand. When the push rod is not moved, the valve will be opened. At this time the pointer indication value on the dial is the opening angle of the valve, and the needle contact rod is counterbalanced to the valve rocker arm (the push rod end). The table is adjusted to zero, then the crankshaft continues to rotate. When the dial pointer returns to the zero position, the push rod is rotated by hand, which is turned to the boundary of the rotation, and the valve is closed, when the indicator on the dial is the valve closing angle.

From valve opening to closing, the angle that the crankshaft turns is the angle of valve opening. Compare the inspection results with the matching gas phase diagram stipulated in the technical documents of the machine. If the super difference is large, the reasons for the excess difference should be found out, such as the serious wear and tear of the transmission gear, the correctness of the installation position of the transmission gear, the damage of the key slot and key of the camshaft, the grinding loss of the cam working surface and so on. The general diesel engine only checks the first cylinder, and the valve timing of other cylinders is ensured by the camshaft.