Evaporative Emissions System: Description and Operation

Fig 4 Evaporative System Monitor:

Evaporative System Components:

PURPOSE
The evaporative emission control (EVAP) system prevents the emission of fuel tank vapors into the atmosphere.

OPERATION
When fuel evaporates in the fuel tank, the vapors pass through vent hoses and tubes to the EVAP canister (charcoal canister).

The canister holds the vapors, until certain operating conditions are met.

When operating conditions are right (Operating temperature reached and time delay elapsed), the PCM allows vacuum through the signal hose to open the valve in the top of the canister. This is done through PCM actuation of the duty cycle EVAP purge solenoid.

This allows intake manifold vacuum to draw the stored fuel vapors into the combustion chamber, where they are burned in the combustion process.

NOTE: The evaporative system uses specially manufactured hoses. If they need to be replaced use only fuel resistant hoses.