On Sedan models, the fuel tank is located in front of the luggage compartment, while on Estate models it is located under the luggage compartment floor.
Fuel from the fuel tank is taken by the fuel pump through the fuel filter and the pipeline and then supplied under pressure to the float chamber of the carburetor. The float and the needle valve regulate the fuel level in the float chamber. Excess fuel is returned to the fuel tank through the return fuel line.
The air filter, installed on the cylinder head cover or on the carburetor, contains a replaceable filter element. A thermostat with a flap is installed in front of the air filter. The thermostat maintains the temperature of the air entering the engine at an optimal level due to the fact that the flap, controlled by the thermostat, ensures either cold air or air heated by the exhaust manifold enters the engine.
In cars with a STROMBERG CD T175 carburetor, the fuel supply when starting a cold engine and the idle speed are controlled by a delay valve. The valve consists of a bimetallic strip, which is heated by an electric current passing through it and controls the vacuum in the diaphragm housing of the control valve. When starting a cold engine, the delay valve closes the vacuum to the diaphragm and the valve remains closed. In the process of warming up the bimetallic plate after starting the engine, the vacuum gradually increases, and the valve, opening, regulates the idle speed. There is also an electromagnetic valve that closes the fuel supply. This valve excludes engine operation after the ignition is turned off, and also limits the maximum engine speed, cutting off the fuel supply if the engine speed exceeds the maximum permissible.
The idle speed and the supply of the air-fuel mixture in cars with a PIERBURG carburetor are regulated by the actuators of the throttle valve and the air flap. The operating parameters of the engines are monitored by sensors installed on the engine and connected to the electronic control unit (ECU). When the engine speed exceeds the idle speed, the actuator of the air flap changes the position of the flap and, consequently, the amount of air entering the engine. When the engine is idling, the actuator of the flap controls the fuel supply by changing the position of the needle in the air jet. The ECU, comparing the idle speed of the engine with the set value, maintains the optimal idle speed in all operating modes of the engine. The throttle position potentiometer is used as feedback in the control system.
Warning! Gasoline is extremely flammable and explosive, so care must be taken when working on any part of the fuel system.
Attention! Work on the fuel system must be carried out in a well-ventilated area, for which you can open all the windows and doors to create a draft.
Material taken from a web resource Mercedesman.ru
Warning! When working on the fuel system, do not use open flames, electric welding or tools that may generate sparks. Make sure that a charged fire extinguisher is in the immediate vicinity of the work area.
Warning! Use goggles to protect your eyes from fuel getting into them. If fuel gets on your skin, rinse the area with plenty of water.
Warning: The container that held the fuel contains fuel vapor and is potentially explosive.
Caution! When working with the fuel system, keep it clean, as dirt that gets into the fuel system channels can block them, which will disrupt the normal operation of the engine.