Rollover Valve: Description and Operation

Pressure Relief/Rollover Valve:

PURPOSE
These rollover/pressure relief valve relieves fuel tank pressure and prevents fuel flow through the fuel tank vent lines should the vehicle be rolled over.

OPERATION
This vehicles are equipped with a dual function rollover/pressure relief valve. The valve consists of a plunger, spring, and an orifice and guide plate. The valve is normally open. In the closed position, force applied by spring pressure seats the plunger against the guide plate, shutting off the flow of fuel vapor from the fuel tank to the evaporative canister. When fuel does not reach the valve, the spring pressure is overcome and the plunger moves away from the guide plate allowing fuel vapor to flow through the valve orifice.

In 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.