Fuel Filler Hose: Description and Operation

Purpose
The fill limiting system is designed to permit an approximate 10 to 12 percent fuel tank volume air space when the fuel tank is filled to capacity. This air space provides for thermal expansion of fuel as well as being an aid to the in-fuel tank vapor vent system.

Features
Fill control is accomplished by the following method:

^ A venting line, attached to the fuel tank filler pipe extends inside the fuel tank.

^ The evaporative emission tube shut off valve senses fuel tank filler cap removal by a change in pressure in the fuel tank. The evaporative emission tube shut off valve closes the flow path from the evaporative emission valve to the evaporative emissions canister (EVAP canister) during refueling to prevent overfilling of the fuel tank.

^ As the fuel level rises to cover the fill vents, pressure rises in the fuel tank, causing fuel to back up. This shuts off the fuel dispensing nozzle.

^ The evaporative emission valve, mounted in the top panel of the fuel tank and the evaporative emission tube shut off valve, also contributes to fill control by controlling pressure in the fuel tank.

^ The vent system is designed to provide an air space, approximately 15 percent of the fuel tank volume, above the fuel level in the fuel tank.

^ The air space allows for thermal expansion of fuel and provides clearance between the fuel and the evaporative emission valve, which is mounted in the top panel of the fuel tank.

^ The clearance is sufficient to allow fuel vapor venting through the evaporative emission valve under all static and most dynamic vehicle conditions.

Construction
The fuel tank filler pipe consists of the restructure, which is a narrow opening in the fuel tank filler pipe covered by a spring steel trap door.

^ The smaller non-leaded fuel nozzle will fit through the narrow opening and push the trap door aside, allowing normal filling. Leaded fuel nozzles will not fit through the narrow opening.

^ The restricted fuel filler is manufactured as an assembly. and must be serviced by removal and replacement with a new fuel tank filler pipe.

^ Fuel tank filler pipes are not to be modified in any way.