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 and outside air enters fuel tank through canister. Fuel filler cap acts as a safety valve if evaporation system fails.
Thermovalve closes and allows manifold vacuum to open purge control valve when engine coolant temperature exceeds set temperature.
When engine is not running, air vent cut-off solenoid valve opens outer air vent passage. This allows float bowl vapors to vent into canister. When engine is running above 500 RPM, air vent cut-off solenoid valve and inner vent solenoid valve open float bowl inner and sub-inner air vent passages to air cleaner. On hot engine starts, when coolant temperature is above 158°F (70°C), delay timer delays opening of inner air vent passage to ease hot engine start up.