Captiva

Evaporative Emission Control System Description

The evaporative emission (EVAP) control system limits fuel vapours from escaping into the atmosphere. Fuel tank vapours are allowed to move from the fuel tank, due to pressure in the tank, through the vapour pipe, into the EVAP canister. Carbon in the canister absorbs and stores the fuel vapours. Excess pressure is vented through the vent pipe and EVAP air inlet to atmosphere. The EVAP canisters store the fuel vapours until the engine is able to use them. At an appropriate time, the control module will command the EVAP purge solenoid valve open, allowing engine vacuum to be applied to the EVAP canister. Fresh air will be drawn through the EVAP air inlet and vent pipe to the EVAP canisters. Fresh air is drawn through the EVAP canister, pulling fuel vapours from the carbon. The air/fuel vapour mixture continues through the EVAP purge pipe and EVAP purge solenoid valve into the inlet manifold to be consumed during normal combustion.

The EVAP system is made up of the following components:

The EVAP canister is a sealed unit with 3 ports.

The canister is filled with carbon pellets used to absorb and store fuel vapours. Fuel vapour is stored in the canister until the control module determines that the vapour can be consumed in the normal combustion process.

The EVAP purge solenoid valve controls the flow of vapours from the EVAP system to the inlet manifold. This normally closed valve is pulse width modulated (PWM) by the control module to precisely control the flow of fuel vapour to the engine.

The EVAP air inlet filters air entering the EVAP canister.