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Diesel engine maintenance.

Date:2018-03-14 Author: Click:

1. Maintenance skills.

1. The phenomenon of "flying cars" of diesel engines and emergency measures.

"Flying car" or speeding is a unique phenomenon of the engine.
The speed of the diesel engine is out of control in the "flying car", and it is getting faster and faster, exceeding the permitted maximum speed and accompanied by a loud noise, which causes the machine parts to be damaged and scrapped.
There are two main reasons for the "flying car" : first, the fault of the governor of the fuel injection pump, which makes it lose its normal adjustment characteristics;
On the other hand is the change of diesel engine speed regulation characteristics, which is characterized by the fact that the governor of the fuel injection pump has no fault, while the diesel engine has extra diesel or oil to enter the combustion chamber during operation.
The phenomenon of "flying car" should take emergency measures, the engine speed up to a certain degree will fail.
Emergency measures to stop speeding are:

(1) quickly pull the accelerator pedal back to the stop position.

(2) with the deceleration device, quickly pull the pressure relief handle to the stop position (or reduced pressure position).

(3) put the brake pedal under the brake pedal in a timely manner, and hold the clutch, so that the engine is out of fire.

(4) quickly disconnect the high pressure oil pipe and stop the oil supply.

(5) quickly pack the air filter with the clothes to shut off the engine.

The above five steps are referred to as "deceleration, decompression, braking, and disconnection".

2. Check methods of each cylinder of diesel engine.

The working conditions of each cylinder of diesel engine can be checked as follows in idle operation:

(1) listen to the sound method: use the stethoscope or the metal rod, near the body of the injector, listen to the sound of the explosion of each cylinder, and the normal sound is similar to the "dangdang" of metal.
If only "ho-ho" continues to make a continuous noise, the cylinder oil supply is too little or does not catch fire in time, such as a loud tapping, indicating that the cylinder is too large or too early.

(2) colorimetric method: when the diesel engine is working normally, the exhaust gas emission is light gray, which is slightly deep when the load is large.
For example, the exhaust gas indicates that the combustible gas combustion is incomplete.
The blue smoke indicates that the lubricating oil enters the cylinder and burns.
White smoke, which means that diesel engine has water, flammable gas not burning also exhaust white smoke.
The exhaust pipe continuously discharge abnormal smoke, indicating that the individual cylinder work is abnormal.

(3) temperature: in the initial stage of diesel engine starts (work after a period of time the exhaust temperature is very high, with the hand touch will burn) by hand touch each cylinder exhaust temperature, can identify each cylinder working condition.
If the temperature of each cylinder exhaust pipe is higher than that of other cylinders, it indicates that the oil supply of the cylinder is on the high side.
If the temperature is low, the cylinder oil supply is small, or not spray oil, or spray oil is not completely burnt or not burning.

(4) pulse method: pinch the high-pressure oil pipe with the hand, and feel the pulsation of the oil when the oil is sprayed, the pulsation is small, the sound is weak, and the oil supply of low temperature is small.
Abnormal sound and high temperature are the oil pressure drop of the injector, the spray oil atomization is bad, or can not catch fire and complete combustion in time.
Large pulsation, strong sound, high temperature cylinder for oil supply.
Low sound and low temperature for injector hole or needle valve card die.

(5) oil breaking method: in order to accurately determine which cylinder has the failure, it can cut off the high-pressure oil pipe to the injector oil road, and stop working to observe the change of the working condition of the diesel engine.
When cutting off a cylinder of oil, if the diesel engine speed and sound does not change or change, indicating that the cylinder works normally.
If intermittent tapping cylinder, when the black smoke, when cutting off a cylinder of oil road, the failure phenomenon disappeared, the fault in the cylinder.

3. Diesel fuel economy 5.

(1) use of fuel - saving smoke reducer.
The economizer is fixed vertically in the front end of the fuel injection pump and connected to the dc power supply.
Use on diesel engine, reduce smoke significant.
It can reduce environmental pollution and save about 5% of oil.

(2) install the inertia supercharger.
Inertia supercharger is installed on diesel engine, which can increase power by 15% and fuel consumption by 3% ~ 5%.

(3) wrap toilet paper in the filter element.
2 ~ 3 layers of absorbent toilet paper are arranged on the diesel oil filter, which can improve the cleanliness of oil and reduce fuel consumption.

(4) add foam plastic air filter element.
In the two-layer filter screen of air filter, an 8-20mm thick foam plastic with good air permeability is added, which can improve the filtering effect, keep the oil normal burning, and reduce the fuel consumption.

(5) turn back the tubing.
The diesel engine is connected to the high pressure oil pipe, and the return oil to the low pressure oil road can ensure normal combustion, and the oil saving effect is very significant.

2. Maintenance skills.

1. "three leaks".
Repair diesel engine, prevent and solve "three leakage" problem, can adopt "five word" criterion, namely strict, clean, wipe, grind, tight.


Strict: the disassembly and installation of parts should be strictly required, comply with the operating rules, strictly prohibit disorderly knock.
If the bolt is screwed, it should be fastened in order and several times. Do not twist in order to prevent the deformation of parts.

Jie: the parts must be cleaned before they are assembled.
If the oil valve and seat contact ring are mixed with minimal sundries, it will not only leak oil, but also directly affect the work of the engine.

Smear: asbestos oil is applied to asbestos MATS, paper MATS, various kinds of screw plugs and oil spills.
The oil should be thin and even, not too thick, and do not wipe the entire surface of the pad, just apply the oil spill.

Grinding: the combination surface of grinding or milling parts. The function is to restore the surface finish and precision, so that the tubing joint or gasket can be kept sealed without oil leakage.

Tight: the tightening of the sealing device should be appropriate, not too tight or too loose.
If the various contact surfaces and sealing nuts of the diesel engine, the appropriate tightening must be maintained.

2. Cylinder pressure off.
In order to ensure adequate cylinder pressure, fitting clearance of the piston and cylinder liner, piston ring, side clearance must conform to the requirements of end, valve and valve seat sealing, injector front end sealing better, cylinder pad, and thickness conform to the requirements.
3. Volume of combustion chamber.
When the diesel engine is repaired, the volume of the combustion chamber will change and the original compression ratio will be changed, which will directly affect the normal operation of the diesel engine.
The factors of the volume change of the combustion chamber are: the piston position is reversed, the cylinder cushion is improper, the crank connecting rod is worn or bent, the eddy chamber is dislocated, and the valve is too large.
When repairing, pay attention to these situations.

4. Timing.
Timing including fuel supply timing and valve timing, if the oil supply is not timing, S195 type, X195 diesel engine can use between the fuel injection pump and the gear chamber cover gasket adjustment, each increase or decrease in 0.1 mm thick gasket, equivalent to the flywheel arc length 6.3 mm.
If the distribution is insufficient, should check and correct the error of the timing gear installed on, and then adjust the valve clearance, valve clearance changes every 0.1 mm, 3 ° crank Angle changes, the equivalent of the flywheel arc length 11.1 mm, adjustment should be paid attention to when the piston compression to the check point on the inlet and exhaust valve clearance (cold) not less than 0.2 mm, in case of parts heat expansion valve closed lax, or valve head impact piston.

5. "three filters".
The technology of air filter is not good, it will make the dust enter the cylinder, and accelerate the early wear of piston ring, cylinder, valve and valve seat, causing difficulty in starting and reducing power.
Diesel oil, oil filter technology condition is bad, can make the impurities into the relevant parts, and between the three big precision coupling early wear and tear, accelerate the crankshaft and bearing wear, severe cases can cause diesel engine early scrapped.


6. Diesel atomization switch.
Plunger vice, delivery valve and injector needle valve deputy technical condition is bad, will cause the fuel injection spray, diesel engine starting difficulty, incomplete combustion, carbon deposit increased, so that engine power, fuel consumption increase, therefore, the fuel oil system, especially the precision matching parts to check carefully.

7. Pass through holes and holes.

(1) pass hole: now, take S195 diesel engine as an example, and the 5 holes of bearing and bushing should be correct in the installation.

A. Main bearing.
Each pair of main bearing oil hole is drilled on the groove, respectively, and the cylinder block, the oil hole on the main journal, when installation, as long as the main bearing flange gap alignment positioning pin, and can prevent the main bearing rotation, guarantee the oil hole alignment, make the lubricating oil road unimpeded, avoid damage.
B. Rocker arm bushing.
When pressing the bushing in the rocker arm, if the hole is not aligned, the rocker shaft and bushing will be burnt due to the lack of dry friction, which will cause the valve clearance to become larger and produce a serious tapping sound.

C. Connecting rod bushing.
Connecting rod small head set oil hole is drilled, and the connecting rod bushing oil hole, the connecting rod little head inside set of copper set, if the two oil hole is not aligned, copper sleeve and the piston pin "dangdang" tapping, or even killed.

D. Starting shaft bushing.
Starting shaft bushing, the installation of two bushing oil hole respectively with the body and gear to cover those corresponding oil grooves are interlinked, or starting shaft and bushing will speed up the wear and tear, caused by oil supply Angle and the distribution of phase change, resulting in a decline in the diesel engine power.

(2) hole clearance: there are four main holes.

A. The oil box cover vent.
The hole plugging, fuel tanks and atmosphere are interlinked, no longer tank top for oil level down there will be a negative pressure, oil supply disruption caused fuel heated evaporation, make the tank pressure increases, will cause oil tank switch place, therefore, this hole is not blocked.
B. The crankcase for air holes.
In pores blocked, inside the crankcase emission is piling up, inside the crankcase pressure increases, can make the engine oil leakage, high temperature exhaust gas mixed with oil, and will also speed up the oil metamorphism, accelerate the parts wear, therefore, must open the hole in the maintenance.

C. Drain oil hole of oil pump.
The drain hole in the oil pump is blocked, which causes a small amount of diesel leakage between the pusher and the pipe to enter the fuel injection pump, and the lubricating oil in the shell can accelerate the wear of the parts. Therefore, this hole cannot be blocked.


D. water pump drain hole.
If the hole is blocked, the leaking water will not discharge the pump body and into the bearing seat, it will accelerate the damage of the bearing. Therefore, it is necessary to dredge the hole during maintenance.


(1) cold running-in.
Fuel injector, with external force driving operation of diesel engine, check the oil pressure and temperature of different parts at the same time, pay attention to listen to the voice parts, cold after running-in, while at high temperature out oil, wash oil filter and oil.

(2) heat runing.
Without heat load running-in, pay attention to each part of the diesel engine working conditions and noise, the thermal load and the stipulated time, always pay attention to each part sound and oil into gas and smoke exhaust, fuel injector oil return, etc., found that the problem should be ruled out in time.



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