Carburetor — removal, inspection and installation

Removal and installation

Disconnect the wire from the negative battery terminal.

Remove the air filter.

Disconnect the accelerator cable and cruise control cable from the carburetor (if it exists).

Disconnect the fuel supply hoses from the carburetor.

Disconnect the connectors from the carburetor.

Disconnect the choke control cable (models with manual choke control).

Disconnect the vacuum hoses from the carburetor, having previously marked their location.

Loosen the nuts and raise the carburetor until the choke heater wire can be disconnected (only on models with automatic choke control), then remove the carburetor from the intake manifold.

Use a screwdriver to remove the gasket or seal from the intake manifold.

Installation is carried out in the reverse order of removal, taking into account the following.

Fill the float chamber of the carburetor with gasoline, which will make it easier to start the engine and reduce the load on the battery.

Replace the gaskets on both sides of the spacer.




After installation, start the engine, check for fuel leaks and check that the fuel level in the float chamber exactly matches the mark on the sight glass (pic. 6.4). If the fuel level is not on the mark, adjust the carburetor.

Check the idling speed of the engine crankshaft and the CO content in the exhaust gases.

Repair and adjustment of the carburetor

Attention! Complete carburetor repair is a complex operation that requires certain skills. An inexperienced motorist should contact a service center or car repair shop.

Attention! Due to changes made by the manufacturer to the design, some elements of the repaired assembly may differ from those installed on your carburetor. However, a car enthusiast with little experience in carburetor repair work is able to identify these differences and carry out repairs.

Disassembly

Before starting work, find out the cost and availability of spare parts for sale. It may be more appropriate to purchase a new carburetor than to repair a knowingly worn unit.

Clean the outside of the carburetor with solvent and dry it. Place the carburetor on a clean, well-lit work bench. Prepare plenty of small containers and markers.




Carefully inspect the throttle and air damper drive rods and the accelerator pump. Draw or label them if they differ from those shown in fig. 6.5.

Disconnect the accelerator pump drive lever from the throttle linkage. Detach the lever spring.

Disconnect the starter air hose from the fitting on the throttle body.

Separate the fast idle pushrod from the choke shaft drive lever.

Remove the eight screws securing the choke body to the carburetor body. The length of the screws is different, so you need to mark their location.

Raise the air damper housing, moving the wires aside. Leave the gasket in place. The piston of the accelerator pump can be removed together with the housing.

Clean the float chamber and remove the fuel and air jets.

Remove the float shaft from the air damper body, remove the float and needle valve, then unscrew the needle valve seat.




Turn out the fuel cut-off valve at idle, then reinstall the spring and accelerator pump piston (pic. 6.6).

Remove the air spring, coast-lean lean solenoid valve, and overrun switch (if they are designed).



If necessary, it is possible to remove the diaphragms of the throttle actuator of the secondary chamber and the air damper together with the brackets. The secondary throttle actuator diaphragm can only be disassembled for inspection, as spare parts cannot be found (pic. 6.7).

If you need to separate the throttle body from the carburetor body, keep in mind that one of the mounting screws is located at the bottom, next to the secondary chamber damper.

Turn out the idle mixture quality screw, remembering the number of revolutions by which it was screwed in, in order to subsequently install the screw in approximately the same place.

Cleaning and checking

Wash all parts with solvent and blow with compressed air. In the absence of a compressor, you can use compressed air from a cylinder. It is not allowed to clean the jets and channels with wire.


Do not immerse the idle shut-off valve, actuator diaphragms, or other rubber or plastic parts in solvent as they may harden, swell, or become irregular.

Make sure that all fuel channels, jets and other calibrated elements are free of dirt and burrs.

Check the top and bottom surfaces of the choke body, carburetor body, and throttle body for damage. Make sure there are no gasket residues on them.

Visually check for wear and ovality of the hole for the drive levers and plastic bushings, replace badly worn parts.

Check the float needle valve and float seat for cleanliness and wear, and replace parts with noticeable gouges and scratches.

Check for deformations on the float, float arms and on the axle, straighten the deformed parts by bending, replace them if necessary.

Check the wear of the rubber cap of the accelerator pump and the presence of cracks on it.

Check the degree of development of the screw for adjusting the quality of the idle mixture (the presence of burrs and annular development).

Check the wear of the air damper plate and the degree of deformation of the rod. In case of severe deformation, bend the rod.



Check air damper diaphragm for leaks and replace if necessary (pic. 6.8).

Check if the air damper turns freely.



If necessary, unscrew the screws, remove and clean the elements of the viewing window of the carburetor body (pic. 6.9).

Check the solenoid valve winding by connecting the terminal to the positive pole of the battery, and the housing to «weight» car. When current passes through the coil, the valve stem must be drawn into the housing. If it doesn't, replace the valve.



The vacuum level in the diaphragm of the pneumatic actuator of the automatic air damper opening device is controlled by a thermal valve, which is screwed into the intake manifold housing. The valve must be airtight at temperatures below 19°C and must open fully at temperatures above 19°C. Temperature spread of operation±3°С. If desired, check the serviceability of the valve by unscrewing it (pic. 6.10).

Assembly

Assembly is carried out in the reverse order of disassembly, taking into account the following.

Replace all gaskets.

Screw in the idle mixture adjustment screw by the same number of revolutions that was determined when it was turned out.

During assembly, make all the adjustments below.

Adjusting the position of the float on the damper body

Before installing the air damper body, it is necessary to measure the distance between the lower surface of the float and the plane of the body (without gasket) and adjust the position of the float. To do this, follow these steps:

• turn the body upside down so that the float drops under its own weight, and measure the gap between the float and the plane of the body. Compare measured value (dimension H in fig. 6.11) with the required value and, if necessary, bend the float tongue;

• turn the body upside down so that the float sinks under its own weight, and measure the distance between the bottom surface of the float and the plane of the body. If the measured value (size L in fig. 6.12) does not correspond to the required, adjust it by bending the float limiter.

Air damper gap adjustment

Apply a vacuum of about 400 mmHg. Art. to diaphragm vacuum tube (pic. 6.13).



Close the choke with a slight push and measure the gap. The nominal clearance is (3,94±0,16) mm. If necessary, adjust the gap, bend the rod (pic. 6.14).

Trigger diaphragm gap adjustment

The check is carried out in the same way as for the air damper opener, but the clearance should be 1.94 + 0.25 mm. If necessary, adjust the gap, bend the rod (pic. 6.15).

Fast idle

Completely close the air damper and use a drill shank or a round gauge to measure the gap between the primary chamber damper and the diffuser wall. The nominal value is given in the technical data. If necessary, adjust the clearance by bending the fast idle drive rod (pic. 6.16).

Throttle Lever Adjustment

Check the opening of the throttle valve of the secondary chamber. It should open only after turning the throttle valve of the primary chamber by 45°, at this angle of rotation, the gap between the throttle valve of the primary chamber and the wall is (6,7±0,5) mm. With a smaller turn of the primary chamber damper, the free play of the secondary chamber damper should not be felt. Also, make sure that the secondary chamber damper rotates freely when the primary chamber damper is fully open. If necessary, adjust by bending the damper actuator lever (fig.6.17).

Attention! Since the opening of the secondary chamber damper is designed for pneumatic operation, it must be operated manually.

Adjusting the quantity and quality of the air-fuel mixture at idle

Install the carburetor, warm up the engine and adjust the engine idle speed and mixture quality. After adjustment, install new protective plugs on the screws.