Fuel Fill Pipe
WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
The fuel fill pipe has a built-in restrictor in order to prevent refueling with leaded fuel. When refueling dual tank applications, fuel is dispensed to both the front and rear fuel tanks at the same time. Once the fill vent is obstructed, fuel backs up the fill pipe and trips the dispensing nozzle. The front fuel tank vent runs into the rear tank to the top of the filler pipe assembly, which in turn vents to atmosphere. The fuel tank vent valves are connected and route to the canister to collect hydrocarbon emissions during operation of the vehicle.