CARBURETED Engines

When fuel tank pressure exceeds a preset value, 2-way valve opens and allows excess vapor to vent into canister. If excessive vacuum forms in fuel tank, 2-way valve opens and outside air enters fuel tank through canister. Fuel filler cap acts as a safety valve if evaporation system fails.

Thermo valve closes and allows manifold vacuum to open purge control valve when engine coolant temperature exceeds preset temperature.