Evaporative Emissions System: Description

All Light and some Heavy Duty Emissions models are equipped with an Evaporative Control System (ECS), designed to prevent raw fuel vapors from escaping to the atmosphere. System consists of a special fuel tank with an expansion section, a venting system which allows only vaporous fuel to be drawn into the system, a pressure-vacuum relief valve in the gas cap to control tank pressure, and a vapor-storing charcoal canister.