Method and system for sealing a fuel filler neck
Methods and systems are presented for diagnosing operation of an evaporative emissions system. The methods and systems include two fuel filler neck valves to control flow of fuel and fuel vapors into and out of a fuel filler neck tube. The two fuel filler neck valves may be biased closed with return springs.
1 . A vehicle fuel system, comprising:
a fuel tank;
a fuel filler neck tube;
a first valve positioned between the fuel tank and the fuel filler neck tube or along the fuel filler neck tube, the first valve opening to allow flow into the fuel tank and closing to prevent flow from the fuel tank; and
a second valve positioned between the fuel tank and the fuel filler neck tube or along the fuel filler neck tube, the second valve opening to allow flow out of the fuel tank and closing to prevent flow out of the fuel filler neck tube,
where the first valve and the second valve open in two different directions,
where the first valve opens in a direction substantially opposite a direction of a flow of fuel vapors, and
where the second valve opens in a substantially same direction as the flow of fuel vapors.
2 . The vehicle fuel system of claim 1 , where the first valve and the second valve are integrated into an assembly.
3 . The vehicle fuel system of claim 2 , where the first valve controls flow through a first through-hole.
4 . The vehicle fuel system of claim 3 , where the second valve controls flow through a second through-hole, the second through-hole extending through the first valve, and where the first through-hole and the second through-hole differ in size.
5 . The vehicle fuel system of claim 1 , where the fuel filler neck tube enters the fuel tank above a level fuel level where the fuel tank is half full of fuel.
6 . The vehicle fuel system of claim 1 , further comprising a carbon filled canister that is in selective fluidic communication with the fuel tank via a vapor blocking valve.
7 . The vehicle fuel system of claim 6 , further comprising a canister vent valve in fluidic communication with the carbon filled canister.
8 . A method for diagnosing an evaporative emissions system, comprising:
opening a first fuel filler neck valve in response to a positive pressure in a fuel tank; and
opening a second fuel filler neck valve in response to a negative pressure in the fuel tank,
where the first fuel filler neck valve is larger in surface area than the second fuel filler neck valve, and where opening the second fuel filler neck valve allows flow through a through-hole formed into the first fuel filler neck valve.
9 . The method of claim 8 , where the second fuel filler neck valve is fully closed when the first fuel filler neck valve is open.
10 . The method of claim 8 , where the first fuel filler neck valve is fully closed when the second fuel filler neck valve is open, and where the first fuel filler neck valve being fully closed when the second fuel filler neck valve is open allows flow through the through-hole formed into the first fuel filler neck valve.
11 . The method of claim 8 , further comprising increasing the positive pressure in the fuel tank via ambient air temperature.
12 . The method of claim 8 , further comprising increasing a magnitude of the negative pressure in the fuel tank via ambient air temperature.
13 . The method of claim 8 , further comprising adjusting a position of an evaporative emissions system valve to increase the positive pressure in the fuel tank.
14 . A vehicle fuel system, comprising:
a fuel filler neck valve assembly comprising a first valve and a second valve, the second valve surrounded by the first valve, where the first valve is configured to selectively close a first through-hole, and the second valve is configured to selectively close a second through-hole, where the second through-hole is part of the first valve, the second through-hole formed into the first valve and extending through the first valve,
where the first through-hole and the second through-hole differ in size.
15 . The vehicle fuel system of claim 14 , where the fuel filler neck valve assembly is positioned between a fuel tank and a fuel filler neck tube, and where the first through-hole is larger than the second through-hole.
16 . The vehicle fuel system of claim 14 , where the fuel filler neck valve assembly is positioned along a fuel filler neck tube.
17 . The vehicle fuel system of claim 14 , further comprising a first spring configured to close the first valve.
18 . The vehicle fuel system of claim 14 , further comprising a second spring configured to close the second valve.
19 . The vehicle fuel system of claim 1 , where the first valve is pivoted about a first hinge to open the first valve and the second valve is pivoted about a second hinge to open the second valve, and where the first hinge and the second hinge are different hinges.
20 . The vehicle fuel system of claim 19 , where the first hinge is positioned on a frame surrounding both the first valve and the second valve, and where the second hinge is positioned on a face of the first valve.