Adhere to the four "don 'ts" to ensure a long service life of diesel engines

Faults of diesel engines in the operation of construction machinery occur from time to time, mainly due to improper application and maintenance of diesel engines. Due to some operators' low technical proficiency or insufficient attention, they adopt some improper operation and maintenance methods when using and maintaining construction machinery. This not only affects the power performance and economy of the engine but also becomes an inducing factor for certain faults, directly affecting the service life of engine components and even the entire machine. Therefore, when using diesel engines, the following four "don's" must be followed.

The speed of the diesel engine should not be too slow

Many engine operators are reluctant to operate diesel engines at their rated speed, believing that a lower speed will prevent malfunctions. In fact, an excessively low speed can lead to some adverse consequences: (1) An excessively low speed will reduce the output power of the diesel engine and lower its power performance; At the same time, reducing the rotational speed of the linkage mechanism will also affect the performance of the working machinery, such as reducing the water output of the water pump and decreasing the head of the water pump. (2) Due to the low rotational speed, the fuel injection pressure decreases, resulting in poor atomization of diesel and incomplete combustion of the mixture, which leads to the formation of carbon deposits. Carbon deposits can easily clog the fuel injector holes, causing a decrease in diesel engine power and black smoke from the exhaust pipe. Excessive carbon deposits can sometimes clog components such as the exhaust pipe muffler and turbocharger, causing the diesel engine to malfunction. (3) When a diesel engine operates at low speed for a long time, the oil pressure drops and the oil circulation speed slows down. As a result, the cleaning capacity decreases, the sealing and cooling effects deteriorate, and the amount of lubricating oil received by the splash-lubricated parts reduces, which intensifies the wear on the surface of the moving parts and shortens their service life. For instance, the wear between the piston, piston rings and cylinder walls increases, the wear of each transmission part of the valve train intensifies, and the service life of the main bearing bush and connecting rod bearing bush decreases, etc. (4) It reduces the reserve power of the diesel engine, causing the diesel engine, which should be operating normally, to be in a state of full load or overload.

Don't add too much engine oil

When adding engine oil, it is better to add more than less. If there is too little engine oil, it will be sucked out, the oil pressure will drop, and the oil will not reach all the lubricated surfaces, which will accelerate the wear of components and even cause bearing seizure accidents. Some users are afraid of burning the bearing shells due to lack of oil and think that adding more engine oil is always better than adding less. Therefore, they often fail to add oil as prescribed, causing the oil to exceed the standard in order to "solve the problem once and for all". In fact, excessive engine oil has many hazards: (1) It is prone to leakage at the front and rear ends of the crankshaft, increasing the consumption of engine oil, polluting the environment, and increasing the difficulty of maintenance. (2) When the engine is running, due to the agitation of the crankshaft, the engine oil foams and deteriorates, increasing the rotational resistance of the crankshaft. Additionally, if the oil level is too high, it will also impede the movement of the connecting rod, thereby reducing mechanical efficiency. (3) Due to the upward flow of engine oil into the combustion chamber, the combustion increases and the consumption of engine oil rises. After engine oil burns, it is prone to form carbon deposits on the piston rings, the top of the piston, the valve seats and the fuel injectors, which can lead to faults such as piston ring seizing and fuel injector blockage. (4) Excessively high oil levels, when stirred by the big end of the connecting rod, are prone to generating oil vapor. When exposed to high temperatures, they can catch fire and burn, causing an explosion of the crankcase. Therefore, it is incorrect to use more engine oil than less. Generally, the oil level should be slightly lower than the mark on the dipstick. If the oil level is too high, it will have the opposite effect.

3. The fuel supply advance Angle should not be too large

Some operators tend to adjust the fuel supply advance Angle of diesel engines a little, and some even exceed the specified value by 2° to 3°. It is believed that if the fuel injection advance Angle is adjusted a bit larger, the engine will work more powerfully. However, both overly large and overly small fuel supply advance angles are harmful: Firstly, the excessively high burst pressure makes it easy for high-temperature gas to seep into the lower crankcase, causing the oil to undergo high-temperature cracking. The oil is also prone to evaporate into oil vapor, leading to a crankcase fire and combustion. Second, the rapid combustion of excessive fuel in the cylinder will increase the thermal load on the piston top, causing overheating and damage to the piston. Thirdly, the vibration of the cylinder liner intensifies, accelerating the formation of cavitation between the cylinder liner and the engine block, leading to damage. Fourth, it will cause knocking on the cylinder, increase the impact force of the piston on the cylinder liner, intensify the vibration of the cylinder liner, and lead to fatigue damage of the cylinder liner. The fifth reason is that an overly large fuel supply advance Angle causes excessive fuel accumulation in the cylinder before the top dead center. After combustion, the burst pressure increases, which will increase the mechanical load on the piston connecting rod and cause damage to these components. Sixth, excessive heat load can cause cracks in the cylinder head and deformation or detachment of the valve seat ring.

4. The temperature of the cooling water should not be too low

There are clear regulations on the water temperature usage requirements for diesel engines, but some operators prefer to set the outlet water temperature very low, with some approaching or even falling below the lower limit of the outlet water temperature. It is believed that when the water temperature is low, cavitation will not occur in the water pump, the cooling water (liquid) will not be interrupted, and the safety factor will increase. In fact, as long as the water temperature does not exceed 95℃, cavitation will not occur and the cooling water (liquid) will not be interrupted. On the contrary, if the water temperature is too low, it is extremely harmful to the operation of the diesel engine: (1) It will cause the temperature in the combustion chamber of the diesel engine to be too low. After the diesel is injected, it is difficult to atomize and burn, and some of the diesel will still be in the form of droplets and discharged with the exhaust gas, with a white smoke color. (2) Incomplete fuel combustion forms gum, causing the piston rings to get stuck in the piston ring grooves and jam the valves. As a result, the pressure inside the cylinder drops at the end of compression. (3) After combustion, some of the products combine with condensate water in the cylinder to form acidic substances, which corrode the cylinder and significantly increase engine wear. (4) When the water temperature is too low, the oil temperature also drops, the oil thickens, its fluidity deteriorates, and the oil pump's oil output decreases, resulting in insufficient oil supply. Coupled with the reduced clearance of the crankshaft bearing, lubrication is poor. Tests have proved that if the coolant temperature drops from 85℃ to 30℃, the engine power will decrease by approximately 8%, fuel consumption will increase by 30% to 40%, and wear will increase by about six times. Therefore, when in use, avoid making the water temperature too low.

The above-mentioned issues are common mistakes made when using and maintaining diesel engines, which should be given sufficient attention by users. During the operation of construction machinery, diesel engines should be used correctly to fully leverage their power and economy, prevent accidents from happening, and extend the service life of diesel engines and their components.