Evaporative Emission Control System

Description and Operation

Description

The Evaporative Emission Control System prevents fuel vapors stored in the fuel tank from evaporating into the atmosphere. When fuel evaporates from the fuel tank, the vapor passes through vent hoses or tubes into the charcoal canister, which temporarily holds the vapors.

If the ECM decides to draw the collected vapor into the combustion chambers under certain operating conditions, it will use intake manifold vacuum to move it.

Circuit Diagrams

Schematic Diagram

Canister

The canister is filled with charcoal and absorbs evaporated fuel vapors in the fuel tank. Collected fuel vapors in the canister are drawn into the intake manifold by the ECM/PCM when appropriate conditions are met.

Purge Control Solenoid Valve (PCSV)

The Purge Control Solenoid Valve (PCSV) is installed in the passage connecting the canister and the intake manifold. It is a duty cycle-controlled solenoid valve controlled by the ECM/PCM signal.

To draw the absorbed vapor into the intake manifold, the ECM/PCM opens the PCSV. Otherwise, the passage remains closed.

Fuel Tank Cap

The ratchet tightening feature on the fuel tank cap reduces the possibility of incorrect installation and ensures the filler neck is sealed. After the gasket on the fuel tank cap contacts the filler neck flange, the ratchet produces an audible click indicating the seal is installed.