Evaporative Emission Control System

Description and Operation

Description

The evaporative emission control system prevents fuel vapors stored in the fuel tank from escaping into the atmosphere. When fuel evaporates in the fuel tank, the vapor passes through the vent hoses or tubes into the canister filled with activated charcoal. The canister temporarily holds the vapor in the charcoal. When the ECM determines that the collected vapor can be used under certain operating conditions, it is drawn into the combustion chambers through the intake manifold vacuum.

Circuit Diagrams

Schematic Diagram

Canister

The canister is filled with charcoal and absorbs evaporated fuel vapor from the fuel tank. The stored fuel vapor in the canister is drawn into the intake manifold by the ECM/PCM when the 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-type solenoid valve controlled by an 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.