Volkswagen Air-Cooled 1970-1981 Repair Guide

Evaporative Emission Control System


Required by law since 1971, this system prevents raw fuel vapors from entering the atmosphere. The various systems for different models are similar. They consist of an expansion chamber, activated charcoal filter, and connecting lines. Fuel vapors are vented to the charcoal filter where hydrocarbons are deposited on the element. The engine fan forces fresh air into the filter when the engine is running.The air purges the filter and the hydrocarbons, which are forced into the air cleaner to become part of the air/fuel mixture, are burned.


Refer to General Information And Maintenance for more details.