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What Causes The Insufficient Power of Diesel Engine

Oct. 18, 2019

After long time operation of diesel engine, problems of insufficient power often occur due to parts wear or operation, improper adjustment, untimely maintenance and so on.there are too main reason which cause insufficient power. The first reason is that the combustion chamber seal is not good, the fuel supply is insufficient, the injector atomization is not good, the gas supply is insufficient, and the fuel supply is not adjusted properly, which results in the incomplete combustion of fuel, which leads to the insufficient power of the diesel engine. The second reason is that the power of friction loss of diesel engine itself is too large due to the excessive wear of parts, poor lubrication, poor cooling, improper installation and so on, which reduces the output power and leads to the insufficient power of the diesel engine. 

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Therefore, when analyzing and troubleshooting the power shortage of diesel engine, starlight Power reminds you that you should grasp the two key problems of burning quality and friction loss. After, Combined with the operator's understanding and mastery of the wear and tear situation and the technical status of the diesel engine parts, several reasons that cause the greatest possibility of the diesel engine power shortage are found out, and then checked and eliminated.

I Insufficient fuel supply

The shortage of fuel supply is one of the common faults in the engine. There are two situations that can easily lead to insufficient fuel supply to the engine,



In the first case, the oil supply resistance is increased due to the half-blocking of the oil path, which makes the oil supply of the machine not smooth. When this happens, the machine performs normally on small loads. In the first case, the oil supply resistance is increased due to the half-blocking of the oil path, which makes the oil supply of the machine not smooth. When this happens, the machine is normal in the small load, but in the large load, the fuel supply is increased because the oil supply is not smooth, the engine will appear obvious fault phenomenon: the speed drops, the sound becomes "hard". Check the oil supply line and diesel oil filter to remove the clogging or replace the filter.


The second situation is that low-pressure oil lines are not strictly closed, resulting in air entry, resulting in air resistance. This kind of fault phenomenon is also obvious. In addition to the lack of power of the machine, the obvious "sizzling" sound can be heard at the tubing joints, increasing the throttle. After air leakage is discovered, retighten the joint screw or replace the gasket according to the situation.


II Air intake and exhaust system failure


When the intake system is blocked, it causes the diesel engine to have insufficient intake, lower power, dull sound and smoke. The most common failure of the intake system is the clogging of the air filter. This fault phenomenon is obvious, easy to judge, as long as the careful cleaning of air filters can be resolved. For turbocharged diesel engines, in addition to air filter blockage, air leakage in the exhaust system will also lead to lack of power. The turbocharged diesel engine is driven by exhaust pressure to drive the turbine to transfer compressed air to the intake pipe, thus increasing the engine power. Therefore, the intake and exhaust system of the turbocharged diesel engine must be completely sealed. If there is leakage in the exhaust system, the exhaust pressure will decrease, the turbocharger speed will decrease, the intake pressure of the engine will also decrease, and the power will eventually decrease. This is manifested as a lack of power. If there is air leakage in the intake system, the power of the machine will also be reduced due to insufficient air intake. The inspection of air leakage in intake and exhaust system can be done by cotton floc, fine cloth strip and so on near the pipe connection. If there is obvious phenomenon of blowing or sucking in the joint, it is indicated that there is air leakage, and the gasket or tightening screw should be installed at the pipe joint.


III Piston group fault


The main failure of piston group is wear and tear of piston assembly. When the piston, piston ring and cylinder liner wear, will result in poor cylinder compression, engine power shortage. The phenomenon is a lack of work, exhaust blue smoke, oil consumption. Severe wear, also accompanied by crankcase gas channeling and engine noise.



Reasons cause the serious wear and tear of the piston group


First, the engine is not fully preheated after starting, in the cold state of sudden acceleration or load. Second, the engine temperature is too high, resulting in excessive expansion of piston components, hardness and strength decrease, so that the parts wear or pull seriously. After this failure, the machine must be overhauled, piston and cylinder liner replaced, and the use of the machine is strictly prohibited, otherwise serious accidents are likely to occur. In order to avoid serious wear and tear, the machine should be operated in accordance with the rules to ensure that the machine works in good condition.


The most important thing is to pay attention to the following three points.


Start after full preheating and then speed up to avoid machine cold tension;

To keep the oil pressure in the prescribed range, not too large or too small;

3. Idle running for several minutes before downtime, make machine temperature drop and then stop, do not stop suddenly in high speed operation.


IV Turbocharger fault

Supercharger is an important part of turbocharged engine, it must maintain good working condition, especially the axial and radial clearance of rotor must be kept within the specified value range. If the supercharger breaks down, it will cause the speed decrease and the inlet pressure lower, resulting in the engine power shortage.


The main features of the breakdown of the supercharger are as follows.


There was a scratch. The main causes of this phenomenon are serious wear of rotor shaft and bearing and damage of seal ring, resulting in oil consumption and noise. When the rotor shaft and bearing wear seriously, affecting the normal operation of the machine, must replace the parts.


The way to avoid accidental wear and tear of the supercharger is to use the equipment in strict accordance with the operating rules. The most important thing is to pay attention to two points.


First, after the engine has just started, it must run at idle speed for 3 to 5 minutes. After the engine oil has formed a cycle in the lubrication system, the oil pressure will rise to the normal value and then speed up and add load;


Second, idle running for about 3 minutes before downtime, and then stop after engine and turbocharger speed drop. It is strictly prohibited that the engine oil pump will stop working and the supercharger will still rotate at high speed after the throttle is suddenly extinguished, which will cause the supercharger to form dry friction due to the lack of oil, aggravate wear and tear, and even damage the turbine in serious cases. The rotor shaft is broken.


V Engine fuel injection time is not correct


Different types of diesel engines have different requirements for fuel injection time, for example, the injection time of Model 4135 diesel engine is 28 °to 31 °before the up-and-down point. Improper fuel injection time will significantly reduce the engine power and damage the engine parts. Fuel injection too early, engine start difficult, black smoke, work vibration increased, voice become "irritable", there is a cylinder knock, the machine temperature rises, exhaust color is thicker than normal. Too late injection, engine start difficult and gray or white smoke, work sounds dull, machine rotation powerless, exhaust black smoke, when the exhaust pipe fire, exhaust pipe temperature significantly increased. The improper injection time is mostly caused by the long time vibration of the machine, which loosens the joint part of the drive shaft and the camshaft of the high pressure oil pump, thus forming a certain angle difference. It is found that the injection time is not at the time, so long as the prescribed data are readjusted to a specified value, And tighten the screws.


VI fittings of a machine abrasion


plunger matching parts, delivery valve matching parts and pintle nozzle matching parts are three main parts of diesel engine. Any failure of them will affect the power output. When the plunger coupling is worn out, the high pressure will not be established quickly, the oil pressure will be too low, and the fuel supply will be insufficient. When the oil valve coupling is worn, it will cause the oil to be cut off, and there will be two times of fuel injection or oil dropping. The speed of the machine is unstable, the vibration is aggravated, and the exhaust is emitting black smoke. When the needle valve couple is worn, the oil droplet will occur, which will make the nozzle glue, seriously affect the injection quality, cause bad atomization of diesel oil and exhaust black smoke. The final result of the damage of the three parts is the power output of the engine, which makes the machine underpowered. These parts can not repair after the damage, can only be replaced as a whole. In addition to the wear and tear caused by normal use, the damage is closely related to the quality of fuel and the operating methods of users. Therefore, in addition to the use of qualified fuel, but also in accordance with the proper operation of equipment. If you try to avoid a sharp acceleration; when long-term parking re-start, check the state of the machine carefully, especially check the flexibility of plunger; regularly check the injector injection pressure and remove carbon deposits, etc.

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