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Failure Analysis Of Insufficient Power Of Diesel Engine

There are many reasons for insufficient power of diesel engine, involving many institutions and systems. The following focuses on the common reasons from the supply system.

Insufficient Oil Supply of diesel engine

1. When the engine is running without load, if you increase the throttle, the speed can only increase slowly; Under load, the engine is obviously weak and easy to shut down, but the exhaust does not smoke; In case of overload operation, turn off the engine and there is a little black smoke.

2 reasons

1) The control valve in the oil passage of the pump cover is jacked up by dirt or worn, resulting in loose sealing.

2) Improper adjustment of fuel injection pump.

3) The speed is too low or fails when the governor works.


4) The diesel filter is blocked or the oil delivery pipeline leaks.

5) The diesel brand does not meet the requirements.

3. Treatment method:

1) Check the control valve and repair or replace it according to the specific situation. And go to a qualified repair shop to adjust the governor.

2) Readjust the fuel injection pump.

3) Adjust the cable length of the rocker arm that stops the oil supply.

4) Clean the diesel filter and seal the oil pipeline.

5) Diesel oil of appropriate brand shall be selected according to season and precipitated.

Improper Adjustment Of Fuel Supply Advance Angle

1 signs

1) When the engine is running at low speed, the engine works rough and has obvious cylinder knocking sound; When the accelerator is increased, the speed can be increased rapidly, the cylinder knocking sound is more obvious, but it decreases, and the cooling water temperature is high.

2) When the engine is running, the exhaust pipe emits black smoke and the cooling water temperature is high. The engine is overheated and sometimes there is gunfire. When the “throttle” is increased, the speed increases slowly.

2 reasons

Supply oil too early or too late.

3 treatment method readjust the oil supply advance angle or replace it, and repair the severely worn adjustment cushion block, roller body, camshaft parts, etc.

Insufficient Air Supply

1. When the engine is running without load, it emits serious black smoke, the sound is stuffy, and the power decreases, especially when accelerating. After loosening the connecting pipe between the air filter and the intake pipe, the phenomenon of black smoke is significantly reduced.

2 reasons


1) The air filter is blocked by dirt, the amount of air entering the cylinder is seriously insufficient, and the fuel gas cannot be completely burned.

2) The exhaust pipe is blocked by carbon deposits.

3) The turbocharger speed decreases.

3. Treatment method:

1) Clean the air filter regularly.

2) Regularly remove the carbon deposit in the exhaust pipe and eliminate the poor combustion of the engine in time.

3) Maintain the supercharger on time and check the turbine and sealing device.

Improper Valve Clearance Adjustment

1. When the engine is running without load, the exhaust pipe emits black smoke intermittently, and there is a slight “clatter” knocking sound on the valve mechanism

2. The reason is that the valve clearance is adjusted too large, so that the inlet valve and exhaust valve open late and close early, and the total opening time of the valve is shortened. As a result, the exhaust gas is not exhausted, the air inlet is insufficient, the engine power is reduced, and the exhaust pipe emits black smoke.

3 treatment method: adjust the valve clearance according to the regulations, and check and adjust the valve clearance regularly in the future.

The Machine Temperature Is Too High Or Too Low

1. The engine water temperature is too high or too low, and the power is insufficient.

2 reasons

1) High water temperature is usually caused by overload operation for a long time, serious scale of cooling system, excessive oil supply or too late oil supply time.

2) The low water temperature occurs shortly after the start-up in winter.

3 treatment method


1) Avoid long-term overload operation of locomotive, remove scale of cooling system, reduce oil supply and adjust oil supply time.

2) After starting the vehicle in winter, it shall not start until the water temperature rises to 40 ℃, and the normal working water temperature shall be maintained at 75 ℃ ~ 90 ℃.

Air Leakage Caused By Wear Of Relevant Parts

1. Signs: air leakage sound in air inlet pipe and exhaust pipe; There are bubbles around the cylinder pad (edge); serious gas channeling at the gasoline filler, blue smoke from the exhaust pipe, and abnormal oil consumption in the oil pan.

2. The valve and valve seat are not closed tightly; The cylinder head screws are not tightened according to the standard torque; Severe oil burn.

3 treatment method

1) Clean, scrape and grind the valve and valve seat.

2) If the joint surface of cylinder head and cylinder block is uneven or warped, scrape or grind it to ensure that the installation projection of cylinder liner is within the specified range, and tighten the cylinder head nuts according to the specified sequence and torque.

3) When the parts of cylinder liner and piston bank are not seriously worn, the piston ring can be replaced, and the cylinder liner can be installed by rotating 90 ℃. If the fit clearance exceeds the specified value, the cylinder shall be bored and the piston with enlarged size shall be replaced.

Loose Or Stuck Moving Parts

1. Signs: black smoke when the engine is running; After parking, rotate the engine and feel great resistance.

2 reasons

1) The adjusting arm of the fixed plunger is loose, and the adjusting fork on the fastening oil supply pull rod is loose

2) The plunger and roller body are stuck, and the spring force of the plunger is too weak or broken.

3 treatment method

1) Fasten relevant parts

2) Repair worn rolling elements

3) Replace the plunger cartridge with standard size and elastic force

Related Reading:

If the diesel engine can also “break the cylinder”, it will save a lot of fuel

Double and a half of high horsepower to check the sales of diesel engines in 2014

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