General System Description

PURPOSE
The Evaporative Emission (EVAP) control system limits fuel vapors from escaping into the atmosphere.

OPERATION
The EVAP transfers fuel vapor from the sealed fuel tank to an activated carbon (charcoal) storage device (EVAP canister). The EVAP canister will store the vapors until the engine is able to use the extra fuel vapor.

When the engine is able to use the extra fuel vapor, the fuel vapor is purged from the carbon element by intake air flow and consumed in the normal combustion process.

TESTING SYSTEM INTEGRITY
The system is required to detect evaporative fuel system leaks as small 0.040 between the fuel filler cap and purge valve. The system can test the evaporative system integrity by applying a vacuum signal (ported or manifold) to the fuel tank to create a small vacuum.