General System Description

Evaporative Emission Control System:

PURPOSE
Controls emission of hydrocarbons from raw fuel.

OPERATION
Fuel is contained within a closed fuel system. When the engine temperature reaches 46° C (115° F) a thermal valve opens allowing fuel vapors stored within the canister to be drawn into the intake flow. The vapors are then consumed in the combustion process.

CONSTRUCTION
The system consists of the following components:
- Canister - stores vapor
- Thermal vacuum valve (TVV) - controls when system operates
- 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