Liquid Vapor Separator: Description and Operation

Fig. 47 Fuel tank vapor valve:

PURPOSE
The fuel tank vapor valve is mounted in the top of the fuel tank and permits fuel vapors to be vented to the charcoal canister, while restricting liquid fuel. A rubber grommet provides a tight seal around the valve in order to keep the vapors from escaping to atmosphere.

Fuel Tank Fuel/Vapor Separator Operation:

OPERATION
Fuel vapors are generated, they enter the valve from the bottom, rise upward past the float, and out through a single vapor line.
If liquid fuel should enter the valve assembly, the float will rise upward and close the orifice. As the fuel is drained back into the fuel tank, the spring attached to the underside of the valve pulls the float downward, exposing the orifice.

NOTE: In the event of vehicle roll-over, the float closes off the valve, preventing fuel from escaping and saturating the charcoal canister.