Evaporative Emissions System: Operation
Expanded fuel (caused by high ambient temperatures) and fuel vapors pass from the fuel tank to the expansion tank. Any liquid fuel entering expansion tank is returned to the main fuel tank as fuel level lowers during normal engine operation. Fuel vapors pass from the expansion tank through a ventilation line to the carbon canister where they are absorbed by activated charcoal. High ambient temperatures will also cause fuel in carburetor float chamber to expand. When the engine is not running, the carburetor float chamber control valve is open to the carbon canister and fuel vapors from the float chamber pass to the canister where they are absorbed by activated charcoal. A ventilation line is connected between the carbon canister and the carburetor. When the engine is running, intake manifold vacuum, acting on this vent line, causes fresh air to be drawn into the canister. This fresh air mixes with the fuel vapors and together they are drawn into the carburetor and intake manifold where they enter the combustion system and are burned. This action cleanses the charcoal and renews its storage capacity.