Fuel Tank: Description and Operation

Fig. 37 Evaporative emission system. (Typical):

Refer to Fig. 37 for a typical evaporative emission system. Complete system schematics are located in ``Vacuum Hose Routings.''




The evaporative emission control system is used to reduce hydrocarbons emitted to the atmosphere from the fuel system. This reduction of hydrocarbons is accomplished by activated charcoal in the carbon canister.
This system consists of a fuel tank with positive sealing filler cap, vapor vent line, carbon canister, vacuum signal line canister purge line, and depending on model, a vapor/liquid separator, a check valve, or both.
Fuel vapors from the sealed fuel tank are led into the carbon canister.
The canister is filled with activated charcoal to absorb the fuel vapors when the engine is at rest or at idling.
As the throttle valve opens and car speed increases, vacuum pressure in the vacuum signal line forces the purge control valve to open and admits an orifice to intake manifold and fuel vapor is then drawn into the intake manifold through the canister purge line.