Internal Tank Vent Valves

There are three internal Tank Vent Valves on the Fuel Tank. During refueling the liquid fuel enters the Fuel Tank through the filler tube and displaces the vapor in the Fuel Tank. The Fuel Tank vapors escape through the Tank Vent Valves to the Charcoal Canister side of the system, including the Recirculation Tube, in a controlled approach to meet On-Board Refueling Vapor Recovery (ORVR) requirements.

• Tank Vent Valves:  The fill limit vapor valve and liquid vapor separator drain valve are open when the fuel level is at lower levels. As the fuel level increases above 75% the float valves start to close. When the tank reaches fuel capacity the float valves are fully closed preventing liquid fuel from entering the Charcoal Canister, Recirculation Tube and Purge Tube. The float valves are also designed to close during a roll over event.
• Grade Vent Valve:  The Fuel Tank has a vapor space that is approximately 10% of the fuel volume to allow for expansion of the Fuel Tank vapors when the tank is full. The Grade Vent Valve is located in this portion of the Fuel Tank. The Grade Vent Valve is a float valve design like the other valves. It is used to allow the vapors to escape into the canister side of the system when the Fuel Tank is full. The float valve will close preventing fuel from entering the canister side of the system if the Fuel Tank is significantly over-filled or during a roll over event.
• Fuel Filler Check Valve:  The inlet check valve at the bottom of the Fuel Filler allows the fuel to enter the tank while also deterring vapor from coming back up the filler tube.