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How to improve the overhaul quality of diesel engine?

- Aug 25, 2018 -

How to improve the overhaul quality of diesel engine?

Correctly judge whether the engine needs to be overhauled.

1, engine power significantly decreased, fuel consumption increased significantly.

Check whether the engine power is significantly reduced, conditional dynamometer can be used to check engine power and torque, no dynamometer can be judged by experience. When the throttle is placed at the maximum fuel supply position, the maximum power output of the engine is only about 60% of the rated power, and the fuel system, valve train and transmission mechanism are not very effective after maintenance and adjustment. When the fuel consumption of 100 km increases obviously, the cause should be ascertained, if it is caused by serious engine wear and tear, the need for overhaul should be considered.


2, cooling water temperature at about 60 degrees is still difficult to start or unable to start.

The comprehensive index of the technical state of the compression system is reduced. If the cylinder pressure gauge is used, the compression pressure of the cylinder is less than 60% of the standard value of the original machine.

3. When the engine is running, there are more serious knocks in the body.


4. The oil consumption rate increases, the oil pressure is too low, and the adjustment effect is not significant.

There is no leakage of engine oil. When the percentage of engine oil consumption relative to fuel consumption reaches 3.5%-4.5%, or the oil consumption has exceeded the prescribed double, or the exhaust pipe emits smoke. At the same time, a large number of oil fumes are discharged from crankcase vents. Crankshaft journal wear exceeds the limit, roundness and cylindricity are out of tolerance.


5, the gap between the cylinder and the piston exceeds the limit value.

Each manufacturer stipulates the limit value of cylinder wear cylindricity error, if one cylinder wear to the limit, the engine should be overhauled. If the wear of cylinder is less than the limit value, but the clearance between cylinder and piston reaches the limit value, the new piston and piston ring should be replaced. If the clearance between the cylinder and the piston is not large, but the engine appears oil channeling phenomenon, new piston rings can be replaced.

6. Accidental damage, if tile burning accident occurs, the engine is close to overhaul, overhaul should be used to restore the performance of the entire engine;


The structure of the engine is complex. Special attention should be paid to the sequence and correct method of disassemble. Otherwise, the engine parts will be damaged, and even the diesel engine can not restore its original accuracy and performance. Therefore, we should have a careful plan before disassemble and make adequate preparations for possible problems and difficulties.

                                                        Correct disassemble

Understand the structure, principle and performance of the engine.

Due to their respective structural characteristics, various types of engines have their own unique features in the disassembly procedure. For example, some diesel engine fuel pumps can be removed directly from the engine block, and some must first remove the starter or the clutch chamber cover at the back of the starter before they can be removed. Therefore, in order to achieve correct disassembly, we must first understand the structure of the machine and not blindly dismantle it.


It can be demolished without demolition, and the demolition must be demolished.

Before disassembly, it is necessary to have a clear idea and have a definite aim. It is unnecessary to disassemble the parts that meet the technical requirements without disassembly inspection. This will not only reduce the workload of assembly and disassembly, but also extend the service life of parts. Because once disassembled and assembled, there is always wear and tear, the moving fittings have been in use, once disassembled it is difficult to install back to the original position. However, if it is difficult to confirm its technical status without dismantling, or if it is considered to be faulty or suspicious after preliminary inspection, it must be dismantled for further inspection or repair.


Use suitable disassembly tools.

Use reasonable tools and equipment to avoid hitting hard, and strictly prohibit direct hammering of machine parts. When hammering, wooden hammers, copper hammers, hammer or cushions should be used with soft materials (copper or copper bars). The precision of the non-removable connection or the assembly with reduced precision after disassembly should be protected as far as possible when it has to be disassembled.


Disassembly should create conditions for assembly.

Precision and complex components should be drawn assembly sketch or transmission system diagram, and the disassembly should also be marked (sequence and orientation), in order to facilitate assembly alignment and reduce adjustment time, and ensure that the original fit clearance is not damaged, to ensure the quality of the assembly after reassembly, such as the disassembly of engine crankshaft bearing cover. For parts with high accuracy and low surface roughness, they should be coated with antirust oil and wrapped with oil paper. For slender parts to be hung, for example, multiple support points should be used to avoid corrosion and deformation. For lubricating oil hole, it should be blocked to avoid falling into dirt or dust.


                                                         Correct assembly

Should be familiar with the mechanical parts of the interconnections and assembly technology requirements. Identify appropriate assembly sites and prepare necessary equipment, instruments, tools and auxiliary materials for assembly, such as paper pads, felt, wire, washer, opening pin, etc.


Parts must be cleaned before assembly.

Because any dirt or dust that exists on the mating surface of a relatively moving part causes severe wear and tear. For the parts and components after drilling, reaming, boring, and the oil channel of the parts, it is necessary to use compressed air or high-pressure oil blowing to remove sediment and metal scrap, otherwise it can not be installed.


Parts should be inspected and identified before assembling.

Parts that are not suitable for technical requirements can not be assembled.


The lubricating parts should be applied when installing the moving parts, so as to reduce the wear and tear during the initial operation of the machine.

Felt washer should be immersed in oil after cleaning. Do a good job in checking parts marking and assembly marks to prevent mistakes.