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(s) with 2 or 3 integral check valves, and outer vent control valve.

Additional components include vacuum switching valve, emission computer, temperature switch, speed sensor, and 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.