Method and system for fuel vapor control
First Claim
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1. A method, comprising:
- monitoring a fuel system including a fuel tank, a vacuum accumulator, a venturi, and a canister between the tank and an engine, including;
during an engine-on condition, storing vacuum in the accumulator via flow through the venturi; and
during a subsequent engine-off condition and while the canister is isolated from the tank;
applying the stored vacuum on the canister, and indicating degradation based on a fuel system pressure change following vacuum application.
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Abstract
A method and system for fuel vapor control in a hybrid vehicle (HEV). The HEV fuel vapor recovery system includes a fuel tank isolation valve, which is normally closed to isolate storage of refueling from storage of diurnal vapors. The method for fuel vapor control includes selectively actuating the fuel tank isolation valve during interrelated routines for refueling, fuel vapor purging, and emission system leak detection diagnostics to improve regulation of pressure and vacuum the HEV fuel vapor recovery system.
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Citations
14 Claims
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1. A method, comprising:
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monitoring a fuel system including a fuel tank, a vacuum accumulator, a venturi, and a canister between the tank and an engine, including; during an engine-on condition, storing vacuum in the accumulator via flow through the venturi; and during a subsequent engine-off condition and while the canister is isolated from the tank;
applying the stored vacuum on the canister, and indicating degradation based on a fuel system pressure change following vacuum application. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method, comprising:
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monitoring a fuel system including a canister, a fuel tank, a vacuum accumulator, and a venturi, the canister coupled between the tank and an engine intake manifold, including; during an engine-on condition, storing vacuum in the accumulator via flow through the venturi; during a subsequent engine-off condition, applying the stored vacuum on the fuel tank before the canister during higher fuel tank pressures, and applying the stored vacuum on the canister before the tank during lower fuel tank pressures; and indicating degradation based on a fuel system pressure response to the vacuum applications. - View Dependent Claims (12, 13)
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14. A method, comprising:
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monitoring a fuel system including a fuel tank, a vacuum accumulator, a venturi, and a canister between the tank and an engine intake, the vacuum accumulator coupled to a purge line connecting the canister to the engine intake, including; during an engine-on condition, storing vacuum in the accumulator via flow through the venturi; and during a subsequent engine-off condition and while the canister is isolated from the tank;
applying the stored vacuum on the canister, and indicating degradation based on a fuel system pressure change following vacuum application.
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Specification