Fuel Evaporation System: Operation

When fuel tank pressure exceeds a preset value, two-way valve opens and allows excess vapors to vent into canister. If excessive vacuum forms in fuel tank, two-way valve opens to allow outside air into fuel tank through canister. Fuel filler cap acts as a safety valve if evaporation system fails.

When coolant temperature is above 131°F/55°C, purge cut-off solenoid valve and thermo valve direct manifold vacuum to purge control valve to draw vapor into throttle body port. When coolant temperature is below this temperature, no vacuum is applied to purge control valve.