SYSTEMS AND METHODS FOR ENGINE-OFF NATURAL VACUUM LEAK TESTING WITH FUEL ENABLEMENT COMPENSATION
First Claim
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1. A method for an evaporative emissions system, comprising:
- adjusting a threshold for an evaporative emissions leak test entry condition based on at least a fuel level;
responsive to the evaporative emissions leak test entry condition being greater than the adjusted threshold, adjusting a parameter of the evaporative emissions leak test based on the evaporative emissions leak test entry condition; and
indicating degradation based on the adjusted parameter.
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Abstract
Methods and systems are provided for increasing the robustness of engine off natural vacuum testing. In one example, following an engine-off event, a heat rejection inference is determined, and further adjusted based on a fuel level and ambient temperature. In this way, an evaporative emissions system leak test may be enabled under conditions where the leak test may otherwise not be executed, thus increasing opportunities for evaporative emissions system leak detection and correspondingly reducing bleed emissions.
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Citations
20 Claims
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1. A method for an evaporative emissions system, comprising:
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adjusting a threshold for an evaporative emissions leak test entry condition based on at least a fuel level; responsive to the evaporative emissions leak test entry condition being greater than the adjusted threshold, adjusting a parameter of the evaporative emissions leak test based on the evaporative emissions leak test entry condition; and indicating degradation based on the adjusted parameter. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method for an evaporative emissions system, comprising:
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following a vehicle-off event, determining an engine heat rejection inference for an engine run time duration; adjusting an engine heat rejection inference entry threshold based on a current fuel level and a current ambient temperature; responsive to the engine heat rejection inference being greater than the adjusted entry threshold, adjusting one or more pressure thresholds for an engine-off natural vacuum test based on the engine heat rejection inference; isolating the evaporative emissions system from atmosphere; and indicating degradation of the evaporative emissions system based on the one or more adjusted pressure thresholds. - View Dependent Claims (14, 15, 16, 17)
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18. A vehicle system, comprising:
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a fuel system isolatable from atmosphere via one or more valves; a fuel level indicator; and a controller configured with instructions stored in non-transitory memory, that when executed, cause the controller to; adjust an entry threshold for an engine heat rejection inference based at least in part on a fuel level; following a vehicle-off event, responsive to an engine heat rejection inference for a vehicle run time duration between the vehicle-off event and a previous vehicle-on event being greater than the adjusted entry threshold, adjust one or more pressure thresholds for an engine-off natural vacuum test based on the engine heat rejection inference; isolate the fuel system from atmosphere; and indicate degradation of the fuel system based on the one or more adjusted pressure thresholds. - View Dependent Claims (19, 20)
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Specification