Starting a cold engine
The air damper is closed due to the operation of the element expanding under the influence of heat. During start-up, the engine vacuum causes intensive fuel suction with a reduced amount of air. After the engine starts, the vacuum starting device, acting on the traction mechanism, causes the air damper to open slightly. The throttle valve is slightly open (additional opening) so as to obtain idle speed with increased engine speed.
During engine warm-up, the element that expands under the influence of heat is heated by the coolant and has less effect on the starting device.
Idling
The throttle valve is closed, fuel flows through the main fuel jet and reaches the idle fuel jet, where it forms a mixture with air. The amount of mixture supplied can be adjusted by the mixture composition screw.
Special slot (hole of the so-called smooth transition) allows to avoid sudden leaning of the mixture when opening the throttle valve of the 1st chamber.
[Text taken from the website: PEUGEOTBOOK]
In the 2nd chamber, the smooth transition system feeds a special circuit. A tube equipped with a jet is immersed in the float chamber. At its end in the cover, a special air jet supplies air, and the mixture reaches the place where the throttle valve opens. The second chamber does not have an idle system.
Normal operation
Fuel is fed through a needle valve into a float chamber, where a float mounted on an axis controls the opening of the needle valve so as to maintain a constant fuel level. Fuel leaves the float chamber through the main fuel jet and is fed into the well. The first chamber is open, fuel is sucked in and mixed with air in the emulsion tubes. The mixture is fed to the diffuser, where atomization occurs. The same process occurs in the second chamber when its throttle valve is open.
Acceleration
When the first chamber throttle valve opens, a cam mounted on its axis pushes a lever that acts on the pump diaphragm via a pusher equipped with a shock-absorbing spring. Fuel is injected (simultaneously in two chambers) through the sprayer. When the throttle valve is closed, fuel is sucked into the pump chamber from the float chamber. Ball check valves separate the suction and pumping circuits.