Fuel Evaporation System: Description
The fuel evaporation system is designed to prevent the escape of raw fuel vapor into the atmosphere. Components include a sealed fuel tank with integral expansion chamber, vacuum relief filler cap, charcoal canister with 2 or 3 integral check valves, bi-metallic vacuum switching valve (Camry, Celica, fuel injected Corolla, Cressida, Land Cruiser, MR2, and Supra), restrictor (Celica GT-S manual transaxle).
Additional components include connecting lines and hoses. When fuel vapor pressure builds in tank, a check valve in canister opens and vapor flows into canister for storage. When vacuum forms in tank, a check valve in canister opens and stored vapor is drawn into fuel tank. If fuel tank vacuum should increase above a pre-set level, a vacuum relief valve opens in filler cap and fresh air flows into fuel tank to prevent tank collapse.