Fuel system — carburetor (Mazda Capella GD)

The engine operates with a two-stage carburetor with sequential activation of the mixing chambers. A mechanical fuel pump is used to prepare the fuel.

5.1.1. Removal and installation

When removing the carburetor with the engine installed, ensure that no foreign objects enter the intake manifold opening. To open only the float chamber of a two-stage carburetor, you do not need to remove the entire carburetor.

Remove the air filter. To do this, remove the air release hose, disconnect (if any) remove the exhaust gas control hoses, loosen the filter mounting bolts, and unscrew the wing nut. Lift the air filter and immediately cover the intake opening with a rag.

Separate the wire plug from the carburetor.

Unscrew the fuel line from the carburetor.

Disconnect (where available) exhaust gas regulation hoses.

Remove the distributor vacuum hose from the carburetor.

Disconnect the throttle control outlet pipe.

Remove the sleeve from the diaphragm mechanism of the vacuum regulator of the ignition advance for the device that doses additional amount of fuel at start-up.

Disconnect the fuel shut-off valve plug connections when the ignition is turned off.

Loosen the carburetor nuts and lift it up.

Place a rag over the intake manifold or close the hood to prevent anything from getting into the engine. The carburetor is installed in the reverse order of removal. Check the idle speed after installing the carburetor (chapter 5.2).

5.1.2. Carburetor repair

To disassemble the carburetor, you need to have a set of special keys for its repair, so that all the carburetor parts can be removed without damage. Place all parts in the order of disassembly on a paper-covered workbench. After removal, clean the parts with clean gasoline and, if possible, dry them with compressed air. When assembling, replace all seals and O-rings. If possible, purchase a repair kit for the carburetor. Disassembly and assembly should be carried out using Figures 128 and 129. The figure shows a typical carburetor, however, within certain designs, slight differences can be found.







Remove the carburetor cover using the drawing 128, this work is also necessary to clean the float chamber.

— Remove the carburetor cover mounting bolts and lift it up. At the same time, remove the mounting bracket for the starter rod and the throttle cable return spring. Remove the sealing caps.

— Remove the return spring.

— Remove the connecting rods and the idle acceleration cam levers. It is held at each end by a clamp, spring, and washer.

— Unscrew the pump rocker arm bolts from the carburetor and remove the rocker arm with rods and levers after removing the spring clamp at the lower end.

— Unscrew the fuel line connection.

• Turn the carburetor so that the bottom surface is on top and unscrew the three visible bolts with a screwdriver. Make sure the bolts have vacuum holes between the inlet holes and are screwed back in the same positions.
• To disassemble the throttle body components, unscrew the diaphragm and remove the diaphragm bolts and throttle levers. Adjusting bolts and springs are also installed in this part and can be unscrewed if desired. Do not remove the throttle valve and throttle shaft.
• If the air damper needs to be removed, file down the ends of the bolts on the damper until they can be removed. The valve should only be removed when it needs to be replaced (or air damper axis).
• Remove the pump outlet weight. Turn the carburetor over by hand. This will cause the spring, ball and outlet weight to fall out.
• Using the assembly drawing, remove all air and fuel jets. The first stage main jet is located at the bottom of the float chamber, the second stage main jet is inside the plug. The fuel line shutoff valve can also be removed.
• Unscrew both diffusers and remove the seal.
• Disassemble the carburetor cover using the drawing 128:

- remove the float axis, remove the float and place it in such a way as not to damage it;



- remove the float needle valve parts;

- unscrew the float needle valve using the included screwdriver-like tool and remove the sealing ring;

- turn the carburetor cover and unscrew the accelerator pump piston mounting bolts. Remove the protective plastics and take the piston out of the cover. Remove the spring;

- remove the rubber seals from the pump piston and take out the piston;

- unscrew the vacuum membrane for the device that doses additional fuel at start-up, after unscrewing the connecting rods and levers.

• Disassemble the throttle valve parts using the drawing 129:

— after removing the rods and levers, as well as the idle speed adjusting bolt, the throttle valve parts cannot be disassembled further.

Clean all parts thoroughly. Jets should never be pierced with wire or other sharp objects. Any suspect parts should always be replaced. The following parts must be subject to special control:

• Open the float chamber needle valve and turn the carburetor cover. If the needle is seated, suck out the air in the inlet valve connection bridge with your mouth. If air is sucked out, the needle is not seated perfectly.
• All the flaps can be replaced, but at this point it is established that it may be better to notice the entire carburetor.
• File down the plate bolts until they can be unscrewed. Remove the air damper shaft. To remove the throttle shaft, you first need to remove the control lever.
• To check the membrane sensor, you need to put a small hose on the connection and try to suck out the air. The membrane should move back and forth inside.

The carburetor is assembled in reverse order using the assembly drawing and the following points:

• Both main jets cannot be confused.
• Since the parts of the first and second stages have the same shape, it is important not to confuse them with each other.
• Install the parts on the top side of the carburetor body in accordance with the drawing 128. Particular attention should be paid to the correct insertion of individual balls and jets. If the air or throttle valve is being replaced, the ends of the bolts (new bolts) must be clamped after tightening so that they cannot come loose again.
• Attach the throttle valve to the carburetor body. Ensure that the bolts are installed correctly in the vacuum holes.
• Certain operations during carburetor assembly are carried out using the description in chapter 5.2.
• After assembling the throttle valve, open the first stage fully and check whether the second stage valve is also open. If there are no faults, the connecting rods between the throttle valves must be bent accordingly.