Depending on the car model, different types of carburetors are installed.
In models with carburetor engines, carburetors of the Sofex, Zenith, Pferburg type are installed, depending on the volume and power of the engine. The designation of the carburetor type is located on the side of the body.
The carburetor serves to form a mixture of fuel and air in the appropriate proportion, as well as to regulate the amount of mixture entering the combustion chamber (at all engine speeds).
The engine power at a given moment depends on the amount of mixture supplied.
The ideal carburetor would be one that would produce the optimal mixture under all conditions. Of course, this is impossible, but carburetors are being equipped with an increasing number of systems, both mechanical and electronic, to optimize the mixture composition.
Main carburetor systems:
- Starting system.
- Idle system.
- Main fuel system.
- Accelerator pump.
- Enrichment system (at full load).
These systems only work at a certain moment (starting system or accelerator pump) or at a certain rotation speed (as an idle system or main fuel system). Since this is not enough, additional auxiliary systems are also used to obtain the optimal mixture composition.
These are systems that enrich or deplete the mixture depending on the ambient temperature, engine temperature, rotation speed, throttle angle, etc. The gasoline injection system performs the same functions as the carburetor. The main differences are in the device. The executing element of the injection system is the electromagnetic valve, which opens under the influence of pulses from the electronic control module.
The feed pump creates pressure in front of the valve. To inject the appropriate amount of fuel, it is enough to open the valve for a longer or shorter period of time. The microprocessor decides how long the valve will be open, which determines the portion of fuel, depending on even more parameters than those given for the carburetor. Among other things, this is the ignition timing, the composition of the exhaust gases in the exhaust pipe, the amount of air passing through the drive manifold, the gear currently engaged, etc. This allows for much more precise control of the fuel supply.
The mechanical fuel pump in models with 1.1 and 1.3 dm³ engines is mounted on the engine head and is driven by a pusher from the camshaft.
In 1.6 and 1.8 dm³ engines, the fuel pump is attached to the engine body and is driven directly through the intermediate shaft cam. Its main task is to suck fuel from the tank and feed it into the carburetor float chamber.
The carburetor consists of a housing in which two check valves are installed. One prevents the fuel column located in the pipe between the pump and the carburetor from moving backwards. The second prevents fuel from entering the fuel tank from the pump during the compression stroke. The fuel tank is located in the rear of the car, under the trunk floor. The filler funnel is located in the rear right wing. Air is removed by an external air removal system.
The fuel system includes a return pipe, which is connected either to a tee located between the carburetor and the fuel pump, or directly to the carburetor float chamber. The narrowing in the return pipe regulates the fuel supply to the tank.
The fuel flow through the return pipe must be under pressure, otherwise the fuel will go into the tank instead of the float chamber.
The return pipe is used to eliminate the pressure in the pipe between the fuel pump and the needle valve after starting the engine. In engines without a return pipe, pressure remains in the pipe after starting the engine. Even a small leak in the needle valve contributes to the fuel getting into the carburetor neck, from where it evaporates and gets out, polluting the environment.
A regular fuel filter is mounted in the feed pipe before the fuel pump, which serves to trap debris and prevents it from entering the carburetor. In models of cars with fuel injection, instead of a carburetor, there is a Bosch K-Jetronic fuel injection system. In this case, the electric fuel pump is mounted in the rear of the car near the fuel tank. The fuel tank supply unit includes a feed pump and a fuel filter. Carburetor (or injection) the fuel system is the most important component of the engine, determining its performance and fuel efficiency.
The carburetor is precisely adjusted to suit the particular engine it is running on and should not be adjusted unnecessarily.
Since most carburetor adjusting bolts are protected by caps, plugs or paint to make it impossible to change their setting, adjustment is impossible without destroying these protections. It is therefore recommended that the adjustments described in this section be made only when necessary. All other work should be entrusted only to a specialist. For most carburetors, repair kits are available that include all the necessary spare parts. In the case of a carburetor that has significant mileage (more than 150000 km) it would be better to replace the entire carburetor with a new one or a refurbished one with a warranty.
Caution: When working on any part of the fuel system, always disconnect the battery ground cable clamp first. Keep all fuel system components clean. Before removing fuel system components or fuel lines, thoroughly clean the areas around these components or connections before disassembling them. Where necessary, install new washers, sealing rings, flexible hoses, clamps, etc
The air filter unit includes a replaceable paper filter insert, as well as an automatic temperature regulator. The temperature regulator serves to switch the valve located in the air filter housing. At low temperatures, this valve opens a channel through which warm air is sucked near the exhaust manifold into the air filter. This improves the conditions for fuel evaporation. The exhaust system in all car models is divided into sections in order to facilitate the replacement of its individual components.
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