Fuel Evaporation System: Description
Carbon-canister storage is the system used for fuel evaporation control on all vehicles. This reduces the amount of gasoline vapor emissions (hydrocarbons).
Fuel vapors are stored in the carbon canister until they can be drawn into the engine for burning during the combustion process. This system burns fuel vapors in the engine rather than venting vapors into the atmosphere.
The fuel tank and carburetor fuel bowl are vented through a hose into a canister containing activated carbon. The carbon adsorbs the fuel vapors when the engine is not operating. When the engine is started, fuel vapors are drawn from the canister into the engine. See Fig 1 and Figure .
Carbon-canisters are either open or closed-bottom in design. Open-bottom canisters draw outside air into system through a filter in bottom of the canister. Some models use an electric solenoid or a thermostatically controlled vacuum valve, combined with ported vacuum, to control the canister purge function. See Fig 2 .