Parisienne V8-305 5.0L (1985)
Fig. 58 Vent & purge valve type vapor storage canister
Vent and Purge Valve Type Vapor Canister
This canister, Fig. 58, is equipped with both a vent valve and a canister purge valve. The rate at which fuel vapor is drawn into the engine is controlled
by a Thermal Vacuum Switch (TVS), which supplies ported vacuum to the purge valve when engine coolant temperature is above a pre-determined
value.
With engine idling at normal operating temperature, the purge valve is forced closed by spring tension and no purging of the canister occurs. On some
models, a small amount of fuel vapor is drawn from the canister through a bleed hole, allowing some canister purge through the PCV system at
idle.
When the carburetor throttle plates are opened, the signal port located above the throttle plates is uncovered and a ported vacuum signal is applied to
the purge valve. Vacuum then overcomes spring tension, opening the valve and allowing vapors to be drawn into the engine for burning.
