DESCRIPTION
All models are equipped with fuel evaporation emission control systems. This closed system is designed to limit amount of fuel vapor released to the atmosphere. The system consists of a special fuel filler cap, specially designed fuel tank, carbon-filled canister, orifice valve and necessary fuel vent vapor lines. All 6-cylinder models with dual fuel tanks and some V8 models use 2 carbon canisters.
FUEL FILLER CAP
Fuel filler cap has one-way vent. This prevents tank collapse, by allowing air to enter tank as fuel is consumed.
FUEL TANK
In most installations, fuel tank is constructed with dome in top. Fuel vapors rise and gather in this dome.
ORIFICE VALVE
On all vehicles, liquid fuel is prevented from entering vapor lines by restricted orifices. Orifices usually are a .050" (1.27 mm) orifice valve, located in emission control valve in fuel tank dome.
Ford Evaporation Emission Control System (F150/250 Regular Cab Shown, Others Similar) Canister must be at lowest point in system. Courtesy of Ford Motor Co. Scheme 19
CARBON CANISTER
Carbon-filled canister acts as storage system for fuel vapors vented from fuel tank and carburetor. Outlet of canister is connected to carburetor bowl vent.
OPERATION
Fuel vapors, trapped in sealed fuel tank, are vented through orifice vapor separator assembly in top of tank.
Vapors then leave separator through a single vapor line, and continue to the carbon canister in engine compartment.
There, they are absorbed by carbon granules, until they are purged from canister by carburetor vacuum once engine is started.
TESTING
Note. Testing information not available.
MAINTENANCE
No regular replacement of components is required with this system. Periodically inspect components for proper functioning.