The nozzle is designed to inject fuel into the engine combustion chamber in a finely atomized state

The engine is equipped with closed-type nozzles with a multi-perforated atomizer and a hydraulically controlled needle

The nozzles are located in the cylinder head (in brass cups) against each cylinder between the valves and are fixed with a bracket.

The nozzle end of the nozzle enters the combustion chamber.

Checking and repairing the MAZ injector

The main parts of the nozzle atomizer 3 with a needle 4, a spring 9 and an adjusting screw 10 are mounted in the body 1 of the nozzle.

Atomizer body 3 is attached to the lower end of the nozzle body with a nut 2, inside which there is a locking needle.

Sealing between the ends of the atomizer and nozzle bodies is achieved by careful processing of these surfaces, followed by grinding them without additional sealing parts.

Just like the plunger pair and the injection valve of the fuel pump, the atomizer with the needle is selected in pairs, and their disassembly during operation is not allowed.

Checking and repairing the MAZ injector

There are four nozzle holes in the lower part of the atomizer body through which fuel is injected into the combustion chamber.

The inner hole of the atomizer body at the bottom passes into a cone, which serves as a seat for the sealing cone of the needle.

The atomizer is fixed relative to the nozzle body with two pins 6.

A nut 11 is screwed into the upper part of the nozzle body, onto which a cap 13 with a sealing washer 14 is screwed.

Adjusting screw 10 is screwed into the nut from below, resting with its shoulders against the spring 9. The other end of the spring through the plate 9 presses on the rod 7, which presses the needle to the spray nozzle with its lower end with a ball, closing the outlet.

The preload force of the spring is adjusted by screw 10, fixed by locknut 12.

In the body, on the side of the thread, a fitting 15 is screwed in, through which fuel is supplied to the nozzle.

A mesh filter 17 is installed at the end of the fitting for the last fuel cleaning before entering the needle.

Rubber seal 18 on the fitting serves to seal the space of the cylinder head in the place where the fitting is covered by the head cover.

A corrugated copper washer is placed under the butt end of the atomizer nut to prevent gas breakthrough.

Checking and repairing the MAZ injector

Checking and adjusting the injectors

After one TO-2, the injectors must be removed from the engine and the pressure at the beginning of the needle lift and the quality of the fuel spray should be checked. It is best to perform this work on the KI-EZEZ device.

The pressure to start lifting the needle should be 200 +15 kgf/cm2. To adjust the nozzle to this pressure, you must:

  • - unscrew and remove the nozzle cap; loosen the adjusting screw locknut;
  • - using the lever of the device, slowly increase the fuel pressure in the nozzle cavity and, observing the readings of the pressure gauge, determine the pressure at which the needle begins to rise, at which fuel injection begins;
  • - use the adjusting screw to set the required pressure to start lifting the needle (when the screw is screwed in, the pressure increases, when the screw is turned out, it decreases);
  • - tighten the locknut of the adjusting screw and check the pressure of the beginning of the needle lift again.

The quality of fuel atomization by the nozzle is checked by moving the instrument lever at a pace of approximately 70-80 strokes per minute.

It is considered satisfactory if the fuel is injected into the atmosphere in a foggy state and is evenly distributed over the cross section of the jet cone and over each nozzle hole.

The start and end of the injection must be clear.

Injecting fuel with a new injector is accompanied by a characteristic sharp sound.

The absence of a sharp sound from used injectors when checking them on a manual stand is not a sign that determines poor-quality operation of the injector.

Injector repair

Checking and repairing the MAZ injector

The nozzle must be disassembled on the fixture in the following order:

  • - unscrew cap 13 of the injector;
  • - loosen the lock nut 12 and unscrew the adjusting screw 10 as far as it will go;
  • - unscrew the nut 11 of the spring, remove the spring 9 and the rod 7 of the injector;
  • - unscrew the nut 2 of the atomizer; remove the atomizer 3, protecting the needle 4 of the atomizer from falling out, in order to avoid breakage fixit is not allowed to remove the atomizer nut without first unscrewing the adjusting screw 10 and spring nut 11;
  • - unscrew nozzle 15 of the injector.

The nozzle parts must be cleaned of carbon deposits and washed in kerosene.

The deposit from the outer surface of the sprayer is cleaned with a brass brush, and the nozzle holes are cleaned with steel wire with a diameter of 0.3 mm.

The inlet channels of the atomizer are cleaned manually with a drill with a diameter of 2 mm.

The internal cavities of the sprayer are cleaned of carbon deposits with brass scrapers, the sharp end of the needle with a brass brush.

Do not use sharp and hard objects, sandpaper or rags to clean the sprayer.

Special attention should be paid to the condition of the nozzle atomizer.

Checking its main parameters is carried out on the nozzle assembly, but before installing it on the nozzle, check the condition of the surface of the needle and the atomizer body.

The body of the sprayer with traces of melting of the nozzle and with a noticeable increase and ellipticity of the nozzle holes is rejected.

Risks and signs of wear on the end surface of the sprayer body are removed by lapping on the plates and finishing to a mirror finish.

If there are matte spots or signs of overheating on the surface of the guide part of the needle, as well as scratches and scratches, replace the atomizer with a new one.

The needle of the atomizer should move smoothly, without jamming and sticking.

The needle (after thoroughly washing the parts of the atomizer in kerosene and lubricating with clean diesel fuel), extended by ⅓ of the length of the guide surface from the body at an angle of inclination of the atomizer axis of 45 °, should smoothly, without jamming, fall to the stop under the action of its own weight.

The injector body may have the following defects: marks, scratches and traces of corrosion on the end surface on the atomizer side, broken threaded connections, mechanical damage and contamination of the fuel channels.

In the presence of scratches, scratches and traces of corrosion on the end surface, the nozzle body is replaced.

The body with damaged threads or with gross mechanical damage is also replaced.

The holes and channels in the body are cleaned in a bath of kerosene with hair ruffs, and the outer surfaces are cleaned with soft metal brushes.

The fitting, cap, spring and atomizer nuts that have crumpled or broken threads are replaced.

It is recommended to blow the nozzle filters with compressed air at a pressure of 5 - 7 kgf / cm2, in the direction opposite to the fuel flow.

The nozzle is assembled in the reverse order of disassembly. In this case, you need to pay attention to the following:

  • - before assembly, all parts of the nozzle must be thoroughly washed in clean kerosene and lubricated with filtered diesel fuel;
  • - install the atomizer before installing the nozzle spring;
  • - tighten the sprayer nut when installing the sprayer assembly on the nozzle body with a torque of 7 - 8 kgcm;

when screwing the nut, turn the spray gun against the direction of screwing the nut until it stops against the locking pins and, holding it in this position, screw the nut on by hand, then tighten it completely.

  • - After tightening the nut, check the ease of movement of the needle: when shaking the nozzle, you should hear the blows of the atomizer needle on the nozzle body;
  • - tighten the fitting when installed in the nozzle body with the application of a torque of 8-10 kgf m, tighten the spring nut - 10-12 kgfm; nozzle cap tightening - 8 - 10 kgcm.

The nozzles on which the atomizers that were in operation are installed must be tested for tightness in the connection between the needle and the atomizer body, for the tightness of the cones and the quality of the fuel atomization.

The density is checked when the nozzle spring is tightened until the start of injection of 300 kgf/cm2.

The time of pressure drop from 280 to 230 kgf/cm2 must be at least 2 s, viscosity 1.4 - 1.5 arb. units at a fuel temperature during the test period of 18 - 22 ° С.

Fuel leakage through the sealing cone and seepage through the thread of the atomizer nut are not allowed.

After checking for density, set the nominal injection start pressure to 200 +15 kgf / cm2, check the tightness of the shut-off cone and the quality of spraying with the fuel injector.

The tightness of the atomizer shut-off cone is determined by the degree of wetting of the atomizer nozzle while maintaining the pressure in the nozzle at 10 kgf/cm2 below the injection start pressure for 1 minute.

The sprayer is unsuitable for further use if 3 drops per minute form and detach from the spout.

The quality of fuel atomization is checked at 90 - 120 injections per minute and nominal fuel supply.

Atomized fuel should be in a misty state. The beginning and end of the injection should be accompanied by a sharp sound.

If these conditions are not met, the sprayer will the nozzle must be removed and cleaned of deposits or replaced with a new one.

Nozzles with nozzles taken from spare parts must be run-in at a special stand.

The tests are carried out on filtered summer diesel fuel at an injection pressure of 185 kgf/cm2.

The injection pressure is regulated by screw 10, when screwed in, the pressure increases, and when screwed out, it decreases.

After adjusting, the screw must be securely locked with the locknut.

The burn-in of the injectors is carried out for 20 minutes with their connection to the TNVL.

The stand pump must be adjusted for a cyclic flow of 120 mm3 at a camshaft speed of 1050 min, the pump rack must be fixed in a fixed position.

After the run-in tests are completed, the nozzle should be checked for density, quality of fuel atomization and tightness.

After setting the fuel injection start pressure to 200 +15 kgf/cm2 , it is necessary to check the quality of fuel atomization; atomized fuel at 40 - 50 injections per minute should be in a foggy state, without individual drops visible to the eye, local thickenings and continuous jets.

The beginning and end of the injection must be clear and accompanied by a sharp sound.

The passage of fuel through the locking cone of the needle at a pressure of up to 185 kgf/cm2 is not allowed.

With a further continuous increase in pressure until injection, a drop is allowed to appear that does not come off the spray nozzle.

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