Comanche 4WD L6-242 4.0L VIN S MFI (1992)
Evaporative Check Valve: Description and Operation
Pressure Relief/Rollover Valve
PURPOSE
The fuel tanks of all Jeep models are equipped with two pressure relief/rollover valves. These dual function valves relieve fuel tank pressure. They
also prevent fuel flow through fuel tank vent hoses in the event of accidental vehicle rollover.
OPERATION
The valve consists of a plunger, spring, and orifice/ guide plate. The valve is normally open. This will allow fuel vapor to vent to the canister. Here
it is stored until it can be consumed by the engine under controlled conditions. If bottom of plunger is contacted by fuel sloshing in tank when
vehicle is cornering, the plunger seats in guide plate at orifice. This will prevent liquid fuel from reaching the canister.
In the event of accidental vehicle rollover, the valve is inverted. In this position the plunger is forced against the guide plate and raw fuel is
prevented from flowing through the valve orifice into the fuel tank vent tube.
