General System Description

Evaporative Emission Control System:

PURPOSE
Controls emission of hydrocarbons from raw fuel.

Canister and Purge Valve:

OPERATION
The purge valve is an integral part of the canister. When the engine is running, vacuum (control vacuum signal) is supplied to the top of the purge valve to lift the valve diaphragm and open the valve. The lower tube on the purge valve is connected to manifold vacuum through the ECM controlled vacuum solenoid valve.
The control valve only opens when sufficient vacuum is applied and the ECM has commanded the solenoid ON, thus preventing purge under conditions of low ported vacuum.


CONSTRUCTION
The system consists of the following components:
- Canister - stores vapor
- Piping and hoses - routes vapor between the components
- Fuel cap - seals fuel tank inlet and allows air to enter the tank to displace fuel that has been consumed (also vents excessive tank pressure)
- In-tank pressure control valve - prevents fuel from escaping if the vehicle rolls over and controls fuel vapor transfer between the tank and canister
- Vacuum solenoid valve - allows the ECM to control purge operation