Evaporative Emissions System: Description

Evaporation Control System (ECS) is designed to reduce fuel vapor emissions from entering the atmosphere through use of a closed fuel tank, and carburetor. Fuel vapors from fuel tank and carburetor are vented to crankcase, on 1970-71 systems, and to an activated charcoal canister on later systems. With the engine not running, fuel vapors are collected in crankcase, early designs, or absorbed by activated charcoal in later designs. When the engine is operating, stored fuel vapors are purged from storage and burned in engine. System components consist of vapor-liquid separator, or ECS tank dome, fuel resistant vapor vent hoses, activated charcoal canister with fiber glass air filter, and purge valve on heavy duty system. All fuel tank gas caps have pressure relief valves to prevent excessive pressure or vacuum conditions within tank.