Method and system for fuel vapor control
First Claim
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1. A method for a vehicle fuel system, comprising:
- during a vehicle-off condition, and while a fuel tank temperature stays within a threshold range,operating a fuel pump to raise a fuel tank vapor pressure to identify leaks in the fuel system, a duration of operating the pump based on a fill level of fuel in a fuel tank.
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Abstract
Methods and systems are provided for performing a vehicle-off fuel system leak test. A vehicle controller may be woken up after a vehicle has been in a key-off condition for a sufficient amount of time to monitor a fuel tank for pressure and temperature stabilization. If the pressure and temperature of the fuel tank is stable, a fuel pump may be operated to raise a fuel tank vapor pressure, and fuel system leaks are identified based on a rate of pressure decay from the fuel tank.
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Citations
20 Claims
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1. A method for a vehicle fuel system, comprising:
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during a vehicle-off condition, and while a fuel tank temperature stays within a threshold range, operating a fuel pump to raise a fuel tank vapor pressure to identify leaks in the fuel system, a duration of operating the pump based on a fill level of fuel in a fuel tank. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method for a vehicle fuel system, comprising:
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monitoring a fuel tank pressure after a vehicle-off event; and in response to a change in fuel tank pressure during the monitoring being less than a threshold, sealing the fuel system by closing a canister vent valve and operating a fuel pump to raise fuel tank pressure to a threshold pressure; and indicating fuel system leaks based on a rate of bleed-down from the threshold pressure. - View Dependent Claims (13, 14, 15, 16, 17)
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18. A vehicle system, comprising:
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an engine including an intake; a fuel system including a fuel tank, a canister, a first valve coupling the canister to the engine intake, a second valve coupling the canister to atmosphere, and a fuel pump coupled to the fuel tank; a pressure sensor coupled to the fuel tank for estimating a fuel tank pressure; and a control system with computer readable instructions for; waking up from a sleep mode following a duration since a vehicle-off event; monitoring the fuel tank pressure after the waking up; and if the fuel tank pressure stays within a threshold range during the monitoring, closing the first and second valves to seal the fuel tank; operating the fuel pump for a duration based on a fuel tank fill level to raise the fuel tank pressure; discontinuing fuel pump operation when fuel tank pressure is at a threshold pressure; and indicating fuel system leaks based on a rate of pressure bleed-down from the threshold pressure. - View Dependent Claims (19, 20)
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Specification