Evaporative Emission Control System Operation

Fig. 14 Evaporative Emission Control system (typical):

This system, Fig. 14, is used to prevent fuel vapors emitted from the fuel tank and carburetor from escaping into the atmosphere. This is accomplished through the use of a non-vented fuel tank, a special fuel filler cap, charcoal canister, vapor separators, check valves, non-vented carburetor, and hoses necessary to connect these components together.
The fuel vapors are absorbed and stored in the charcoal canister until the engine is started. These vapors are then drawn either through the air cleaner snorkel or through a ported vacuum port in the carburetor (depending on application) and burned along with the normal air fuel mixture.