Evaporative Emission Control System

Vacuum Routing Schematic:

PURPOSE
The Evaporative Emission Control System prevents the release of unburned hydrocarbons (from liquid gasoline or gasoline vapor) into the atmosphere.

OPERATION
When pressure in the fuel tank is below 21 kPa (3 psi), the pressure relief/rollover valves open. This allows fuel vapors to flow to the evaporative canister where they are absorbed by a charcoal mixture. This prevents excessive pressure build-up in the fuel tank. Most canisters are equipped with a calibrated orifice at the inlet to the canister. Refer to the appropriate Vacuum Hose Routing Schematic for orifice location.

Fuel vapors stored in the canister are used during combustion once the vehicle is again operated. The manner in which vapors are removed from canister (canister purge function) and into engine for combustion, will vary. This will depend on engine and vehicle application.