Evaporative Emission (EVAP) control system prevents the escape of fuel vapors from a vehicle's fuel system. A purge valve opens when the engine is running, allowing a vacuum to pull fuel vapors into the engine. EVAP codes are common and can be a challenge to fix, even for professional mechanics.
- The evaporative control; system captures the gasoline vapors that come from the fuel tank and carburetor float bowl and prevents them from escaping into the atmosphere.
- When the engine is not running. fuel vapors feed on the tank and float the bowl into a carbon or charcoal canister. The activated charcoal in the canister traps or adsorbs the fuel vapors. Adsorb means gasoline vapors are trapped by sticking to the outside of the charcoal particles
- When the engine starts, fresh air flows through the canister and picks up the gasoline vapor. The air then flows into the intake manifold and becomes part of the air-fuel mixture entering the engine cylinders. In this condition, the clearing of the trapped fuel vapor from the canister is called purging. Running the engine removes or purges the vapor from the canister.