Adjusting the throttle drive and carburetor air damper
When the drive is properly adjusted, it is necessary that the throttles and air damper open and close in accordance with the positions of the pedal and manual control buttons
Incomplete opening of the throttles leads to a decrease in engine power, and insufficient closing of the throttles causes increased engine speed when idling and increased fuel consumption.
If the air damper does not open completely, the fuel mixture becomes richer, which causes excessive fuel consumption, and if it is not closed completely, starting a cold engine becomes difficult.
First, adjust the foot and manual throttle drives, and then the air damper drive.
The foot drive is adjusted using a threaded fork on the carburetor rod and a threaded rod of the throttle control pedal so that when the throttles are fully opened, the pedal does not reach the floor by 3-5 mm.
The travel of the throttle control pedal must be at least 160 mm.
After completing the adjustment, the rods are secured with locknuts.
The manual drive of the throttles is regulated by a clamp, which is installed at the end of the drive cable so that when the drive handle is fully retracted, there is a gap of 2.0-3.0 mm between the clamp and the bracket mounted on the rod.
This gap is necessary so that when the manual throttle control handle is retracted, the return spring ensures that the throttles are covered.
The chokes in the closed position should tightly cover the channels of the mixing chamber; A gap of no more than 0.05 mm is allowed between the channel wall and the edge of the throttles.
When adjusting the air damper drive, you must install the manual control handle so that it does not reach the stop of the cabin shield by 2.0-3.0 mm.
In this position, with the air damper fully open, connect the drive cable to the damper lever and clamp it with a screw, then secure the cable sheath in another clamp.
In the closed position, that is, with the handle fully extended, the air damper should completely cover the neck channel for air passage; A gap of no more than 0.15 mm is allowed between the channel wall and the edge of the damper.
Adjusting low engine idle speed. Adjusting the idle speed should ensure stable operation of the engine at idle speed with the lowest fuel consumption.
Adjustment is carried out with the engine running, warmed up to normal temperature (80-95°C) of the coolant, with normal clearances in the valves and between the electrodes of the spark plugs and with the air damper fully open.
In Fig. Figure 1 shows a diagram by which you can trace the operation of the idle system of the K-88A carburetor and the process of adjusting the carburetor. The K-88 carburetor circuit is similar.
At low engine idle speeds, vacuum from the intake manifold is transmitted through hole 43 of the idle system and rectangular hole 42 into channel 44.
Under the influence of vacuum, fuel from the carburetor float chamber, passing the main jet 47, is directed to the idle jet 6 progress.
To obtain the required mixture composition, air is added to the fuel, entering through cutout 7.
The resulting emulsion enters the mixing chamber through holes 43 and 42.
When leaving the holes, the emulsion is mixed with the main air flow passing into the chamber through the gap formed by the edge of the throttle 45 and the wall of the mixing chamber.
When adjusting, it should be taken into account that the K-88A carburetor is a two-chamber carburetor and that the qualitative composition of the combustible mixture in each chamber is regulated by its own adjusting screw 41, independently of the other chamber.
It must be remembered that when tightening the adjusting screws, the mixture becomes leaner, and when unscrewing them, it becomes richer.
In Fig. Figure 4 shows how to adjust the K-88A carburetor on a ZIL-1Z0 car.
Before starting the engine and starting the adjustment, you need to tighten the screws 1 for high-quality idle speed adjustment as far as possible, but not too tightly, and then unscrew each three turns.
After this, start the engine and perform a quantitative adjustment, i.e., set the throttle opening with the thrust screw 2 to the minimum opening at which the engine should operate quite stably.
Then you should gradually tighten one of the screws 1 with each test by 1/4 turn until the engine begins to operate with obvious interruptions due to a large lean mixture in the cylinders.
After this, enrich the mixture by unscrewing screw 1 1/2 turn.
Perform the same operations with the second adjusting screw 1.
Having adjusted the mixture composition, you should try to reduce the idle speed by gradually unscrewing the thrust screw 2 of the throttles, and then again try to lean the mixture composition with both screws 1 in turn, as indicated above.
Usually, after two attempts, it is possible to find the correct position for all three adjusting screws and thereby complete the qualitative and quantitative adjustment of the low idle speed of the engine.
To check the adjustment, press the throttle pedal and immediately release it. If the engine stops, the idle speed must be increased.
With a properly adjusted carburetor, the engine should run stably at 400-500 rpm of the crankshaft.
The method of adjusting the carburetor on the ZIL-1Z1 car is the same as on the ZIL-130 car.
Control and adjustment of K-88 and K-88A carburetors can be performed using simple installations and using templates that can be made in a motor transport company.
Checking the fuel level in the float chamber
The main reasons for an increased or decreased fuel level in the carburetor float chamber may be the following: leaking float, incorrect weight (normal weight 18.7-19.8 g), jamming or leaking fuel supply valve 2 (Fig. 1).
One of the reasons for an increased or decreased fuel level in the float chamber may also be incorrect installation of the fuel supply needle valve when assembling it on the carburetor air neck body.
Therefore, before you start adjusting the fuel level, you need to make sure that all components and parts included in the float mechanism are in good condition.
The tightness of the assembled fuel supply needle valve is checked using a vacuum installation (Fig. 5, a). The needle valve assembly 4 with gasket 5 is installed in the housing 6, the tube of which is screwed into the tee 7.
The installation works as follows
When the tap 8 is open and the piston 9 is moved using the rod 10 in the direction indicated by the arrow, a vacuum is created in the cylinder, under the influence of which the needle valve is pressed against its seat, and the water in the glass tube 2 rises up.
The level of the water column is equal to the vacuum in the cylinder.
The piston must be moved until the water is in glass tube will reach a height of 100 cm on a scale of 3 from the water level in tank 1, after which tap 8 should be closed.
If the needle valve is sealed, then the water in the glass tube will not fall down; if there is no seal, the water will fall down.
The permissible value of the fall of the water column in 0.5 minutes can be no more than 10 mm on a scale of 3.
To obtain tightness, grinding of the needle valve to the seat is allowed. If after this the seal is not obtained, the needle valve must be replaced with a new one.
When installing the needle valve assembly 12 (Fig. 5, b) on the air neck body 11, it is necessary to correctly maintain the distance from the top point of the needle valve sphere to the plane of the neck body.
This size is adjusted with spacers 14, and it should be equal to 13.5-13.8 mm according to template 13.
The fuel level in the carburetor float chamber at a pressure in front of the needle valve is within 125-170 mm Hg. Art. should be 18-19 mm from the upper split plane of the float chamber body.
You can check the fuel level in two ways
The first method is that when the engine is running at low idle speed, you should unscrew the control plug (Fig. 6, a) and through the control hole located at eye level (Fig. 6 , b), monitor the fuel level.
If the level is correctly adjusted, the fuel will be visible, but it should not leak out of the hole.
The second method of checking is to unscrew the plug that closes the valve channel of the mechanical economizer, and in its place screw in adapter 1 (Fig. 7), ending in glass tube 2 with marks marked on it , indicating the limits of fluctuation of the fuel level in the float chamber.
The fuel level in the float chamber should be up to the upper or lower mark, i.e., at a distance of 18-19 mm from the split plane of the float chamber.
To obtain the correct fuel level in the float chamber (if the needle valve is installed correctly), bending the float bracket is allowed: at a high level, the float must be bent down, at a low level, upward.
Checking the throughput of the carburetor metering elements
Maintaining carburetor jets includes not only washing and purging their calibrated holes, but also checking their flow capacity.
The efficiency of the carburetor, and therefore the operation of the engine, depends on the normal flow rate of the jets, which is checked once a year.
The throughput of the jets is checked using two types of devices: to check the jets for water outflow with an absolute determination of flow and to check the jets with a relative measurement of water flow.
Instruments with absolute determination of jet capacity provide greater accuracy and stability of readings compared to devices with relative determination.
Therefore, it is better to use a device with absolute definition (Fig. 8).
The throughput of the nozzle is expressed in cubic centimeters of water flowing through the nozzle being tested in 1 minute, at a height of the water column of 1000 ± 2 mm (counting from the supporting surface of the nozzle) at a temperature of 20 ± 1 ° C, which is determined by thermometer 4.
When checking the throughput, the jets must be installed in the devices so that the liquid flows through them in the same direction as in the carburetor.
Before checking for flow, all jets must be cleaned of burrs, dirt and oil, washed in clean gasoline and blown with compressed air.
During calibration, the dimensions of the nozzle holes are adjusted to the required size by gradually expanding them.
Chasing or soldering of holes to reduce their throughput is not allowed.
If the diameter of the calibrated hole of the nozzle is larger than normal, the nozzle must be replaced with a new one.
Dosing elements are checked in the following order.
Water from the upper tank 1 (see Fig. 8) through tap 2 through the tube enters the float chamber 16, in which the float mechanism maintains a constant water level equal to 1000 mm from the supporting surface of the jet being tested.
From the float chamber, water through tap 15 and tube 13 enters housing 12, rises through glass tube 3 and simultaneously flows out through the nozzle 5 being tested, screwed into holder 11.
The water flowing out through the nozzle being tested enters the measuring beaker 6 or tray 7, from where it enters the lower tank 10 through tap 9.
From the lower tank, water, as needed, can be supplied with compressed air from a compressor or hand pump to the upper tank 1 through tube 14; taps 8 and 9 must be closed.
After filling the upper tank, first open tap 8, and then tap 9 to avoid overflowing tray 7 with water.
To determine the throughput of the nozzle, you need to place a measuring beaker 6 under the flowing stream of water and use a stopwatch to determine the time it takes to fill it with water.
The throughput of the nozzle is determined as the quotient of dividing the amount of water in the beaker in cubic centimeters by the time of filling it in minutes.
If the flow of water stops after exactly 1 minute, then its volume in the beaker will indicate the throughput of the jets in cubic centimeters per minute.
For normal operation of the carburetor, it is also necessary to check the tightness of valve 34 (see Fig. 1) of the mechanically driven economizer; the check can be carried out on a vacuum installation (see Fig. 5, a) in the same way as the fuel supply needle valve is checked.
You should also inspect the fit of the ball 29 (see Fig. 1) and needle 40 valves of the accelerator pump to their seats, as well as their freedom of movement.
It is also necessary to check the correct operation of the moving mechanisms of the economizer valve with a mechanical and pneumatic drive, the accelerator pump, the air damper 15 and the chokes 45, the freezing and jamming of which is not allowed.
When checking the needle valve 40, you need to unscrew the hollow screw 14 and remove the valve, remembering that the valve is not secured in its seat, and therefore can spontaneously fall out and get lost.