Evaporative Emission Control System Description

Evaporative Emission Control System Description

(1) EVAP Canister Purge Solenoid Valve

(2) EVAP Canister

(3) Fuel Fill Cap/Fill Neck

(4) Fuel Tank

(5) EVAP Air Inlet

(6) EVAP Vent Pipe

(7) EVAP Vapor Pipe

(8) EVAP Purge Pipe

The evaporative emission (EVAP) control system limits fuel vapors from escaping into the atmosphere. Fuel tank vapors are allowed to move from the fuel tank, due to pressure in the tank, through the vapor pipe, into the EVAP canister. Carbon in the canister absorbs and stores the fuel vapors. Excess pressure is vented through the vent pipe and EVAP air inlet to atmosphere. The EVAP canisters store the fuel vapors 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 vapors from the carbon. The air/fuel vapor mixture continues through the EVAP purge pipe and EVAP purge solenoid valve into the intake manifold to be consumed during normal combustion.

EVAP System Components

The EVAP system is made up of the following components:

•	The EVAP canister purge solenoid valve

•	The EVAP canister

•	The fuel fill neck/fill cap

•	The fuel tank

•	The EVAP air inlet

•	The EVAP vapor pipe

•	The EVAP vent pipe

•	The EVAP purge pipe

EVAP Canister

The EVAP canister is a sealed unit with 3 ports.

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

EVAP Purge Solenoid Valve

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

EVAP Air Inlet

The EVAP air inlet filters air entering the EVAP canister.