Liquid Vapor Separator: Description and Operation

Fig. 47 Fuel tank vapor valve:

All fuel tank vapor valves, Fig. 47, use a small orifice which allows only vapor and not fuel to pass into the line going to the vapor storage canister. This assembly is mounted on the fuel tank. Fuel vapors trapped in the sealed fuel tank are vented through the vapor valve assembly. The vapors leave the valve assembly through a single vapor line and continue to the charcoal canister for storage, until they are purged into the engine. On vehicles equipped with fuel/vapor return lines, vapors created in the fuel line is continuously vented back to the fuel tank. This prevents engine surging from fuel enrichment.