Evaporative Emission Control Canister: Description and Operation

Fig. 53 Charcoal canister w/purge control valve:

DESCRIPTION
The carbon canister, Fig. 54, is a carryover design of the one used in previous years, except that routing of the vapors has been change. The carbon has been improved to handle the increased demands which the system has placed on it. The vapors in previous years were fed to the carbon bed from the bottom up. On 1978, the vapors enter the top of the purge side of the canister and travel in a "U" shape pattern to the fresh air vent side.

On vehicles equipped with a dual canister system, two canisters are linked together in which the secondary canister is used for "spill over" fuel vapors. This system is called a "series purge". In a "split purge" system the primary canister collects carburetor bowl vent vapors, and the secondary canister collects fuel tank vapors.