Fuel Evaporation System: Operation
The fuel evaporation system is controlled by a bi-metallic vacuum switching valve (BVSV) and a vacuum control valve (VCV). At low engine temperature, ported vacuum to the VCV is cut off and no fuel vapors are drawn into intake manifold.
When the engine is warmed to normal operating temperature, BVSV opens and allows ported vacuum to reach the VCV. When engine is running above idle, the ported vacuum signal opens VCV and manifold vacuum purges canister, drawing vapors into combustion chambers for burning.