Methods and systems for diagnosing fuel tank oil-canning
First Claim
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1. A method for a fuel system, comprising:
- determining a fuel tank pressure based on a fuel system sensor;
indicating fuel tank oil-canning responsive to a higher than a threshold rise in the fuel tank pressure following application of vacuum to a fuel tank while each of a fuel temperature and a fill level remains unchanged; and
responsive to the fuel tank oil-canning, discontinuing the application of vacuum and venting the fuel tank to atmosphere.
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Abstract
Methods and systems are provided for detecting a fuel tank oil-canning event during conditions when a vacuum is applied to the fuel tank, such as during a fuel system leak test or during purging of a fuel system canister. In one example, a method may include comparing the fuel tank pressure changes during a leak test to changes in fuel tank temperature or fill level and indicating fuel tank oil-canning in response to a higher than threshold rise in fuel tank pressure during or following application of vacuum to the fuel tank while each of a fuel temperature and fill level remain unchanged. By detecting fuel tank oil-canning accurately, appropriate countermeasures can be taken.
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Citations
20 Claims
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1. A method for a fuel system, comprising:
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determining a fuel tank pressure based on a fuel system sensor; indicating fuel tank oil-canning responsive to a higher than a threshold rise in the fuel tank pressure following application of vacuum to a fuel tank while each of a fuel temperature and a fill level remains unchanged; and responsive to the fuel tank oil-canning, discontinuing the application of vacuum and venting the fuel tank to atmosphere. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method, comprising:
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sealing a fuel tank after pulling down fuel tank pressure to a threshold vacuum; and responsive to each of a fuel temperature and a fill level remaining unchanged while the fuel tank pressure decreases below the threshold vacuum and subsequently rises at a threshold rate after the sealing, inferring fuel tank oil-canning and unsealing the fuel tank. - View Dependent Claims (11, 12, 13, 14)
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15. A fuel system, comprising:
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an engine receiving fuel from a fuel tank; a canister for storing fuel tank fuel vapors; a canister vent valve (CVV) in a vent line coupling the canister to atmosphere; a canister purge valve (CPV) in a purge line coupling the canister to the engine; a fuel level sensor coupled to the fuel tank for estimating a fill level of the fuel tank; a temperature sensor coupled to the fuel tank for estimating a temperature of the fuel tank; and a controller with computer readable instructions stored on non-transitory memory for; performing a fuel system leak test and pulling down fuel tank pressure to a threshold pressure by opening the CPV and applying engine vacuum to the fuel tank; after vacuum pull-down, sealing the fuel system; and responsive to a higher than a threshold rise in fuel tank pressure while each of a temperature and fill level of the fuel tank remains unchanged, indicating fuel tank oil-canning; and responsive to the fuel tank oil-canning, setting a diagnostic code; unsealing the fuel system and aborting the fuel system leak test. - View Dependent Claims (16, 17, 18)
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19. A method, comprising:
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determining a fuel tank pressure based on a fuel system pressure sensor; determining an estimation of fuel slosh based on output from one or more of a fill level sensor and a vehicle motion sensor; estimating a fuel temperature based on a temperature sensor coupled to the fuel tank; indicating fuel tank oil-canning responsive to a higher than a threshold rise in the fuel tank pressure following application of vacuum to a fuel tank while each of the fuel temperature and a fill level remains unchanged, the fill level determined based on the estimation of fuel slosh; and responsive to the fuel tank oil-canning, discontinuing the application of vacuum and venting the fuel tank to atmosphere.
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20. A fuel system, comprising:
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an engine receiving fuel from a fuel tank; a canister for storing fuel tank fuel vapors; a canister vent valve (CVV) in a vent line coupling the canister to atmosphere; a canister purge valve (CPV) in a purge line coupling the canister to the engine; a fuel level sensor coupled to the fuel tank for estimating a fill level of the fuel tank; a temperature sensor coupled to the fuel tank for estimating a temperature of the fuel tank; and a controller with computer readable instructions stored on non-transitory memory for; performing a fuel system leak test and pulling down fuel tank pressure to a threshold pressure by opening the CPV and applying engine vacuum to the fuel tank; after vacuum pull-down, sealing the fuel system; and responsive to a higher than a threshold rise in fuel tank pressure while each of a temperature and fill level of the fuel tank remains unchanged, indicating fuel tank oil-canning; setting a diagnostic code; unsealing the fuel system and aborting the fuel system leak test; and responsive to the higher than the threshold rise in fuel tank pressure while one or more of the temperature and fill level of the fuel tank changes, indicating no fuel tank oil-canning, unsealing the fuel system, and aborting the fuel system leak test.
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Specification