Abstract: A method for operating a fuel system is disclosed. The method includes sequentially purging fuel vapors from each of a plurality of regions of a canister. Purging a region includes opening an air inlet valve associated with that region and maintaining air inlet valves associated with each other region closed to direct fuel vapors to at least one purge outlet.

Abstract: A method and system for conducting leak detection in an evaporative emission control system. The method performs a pressure-based leak test at selected intervals. The pressure-based test includes pressurizing the system, using a pump. Then, the system monitors pressure for a selected period. If system pressure falls below a threshold value during the selected period, the system identifies an initial leak. Upon identifying the initial leak, the system substitutes a vacuum-based leak test at each selected interval. The vacuum-based test includes evacuating the system, using the pump. The system then monitors system pressure for a selected period. If system pressure rises above a threshold value during the selected period, then the system identifies a subsequent leak. Upon receiving notification that the initial leak has been repaired, the system returns to pressure-based leak testing. Where a single pump is used, that pump is configured both for system pressurization and evacuation.

Abstract: Embodiments for controlling fuel vapors are disclosed. In one example, a method comprises during a purge of a fuel vapor canister, adjusting a heater of the fuel vapor canister based on a rate of a purge flow exiting the fuel vapor canister and a concentration of hydrocarbons released from the fuel vapor canister. In this way, a fuel vapor canister purge efficiency may be increased.

Abstract: Methods and systems are provided for identifying leaks on each of a fuel tank and a canister side of a fuel system using a single leak check module. A position of a switching valve coupled in the vapor line of the fuel system is adjusted to selectively couple the leak check module to either the fuel tank or the canister. Leak is detected based on a change in pressure at a reference orifice of the leak check module following applying of vacuum from a vacuum pump.

Abstract: A method for verifying the reliable operation of a fuel tank pressure transducer positioned within a fuel tank of a PHEV. The method detects the initiation of a refueling cycle, which leads to opening a system vent valve positioned between a carbon canister and a system vent, and opening a fuel tank isolation valve. A controller monitors fuel system pressure within the fuel tank and at the vent valve, and that device determines rates of change of the fuel system pressure within the fuel tank and at the outlet vent. Reliable operation of the fuel tank pressure transducer is indicated upon a determination that the rates of change of the fuel system pressure in the fuel tank and at the outlet vent are uniform within a predetermined range.

Abstract: A system for a vehicle, comprising: a tank pressure control valve coupled in a first conduit between a fuel tank and a fuel vapor canister; a refueling valve coupled in a second, different, conduit between the fuel tank and the fuel vapor canister, the second conduit in parallel to the first conduit. In this way, two smaller, less complex valves may be utilized to control fuel tank vapor purging and fuel tank depressurization during refueling. This in turn may lower system cost and increase system functionality.

Abstract: Methods and systems for cleaning a pressure relieve valve for a fuel tank are disclosed. In one example approach a method for cleaning a pressure relief valve that is normally activated at a preset negative pressure in a fuel system comprises, during a test cycle, reducing fuel system pressure to a predetermined pressure which is higher than the preset pressure, and measuring pressure changes in the fuel system; and when not in the test cycle, periodically reducing the fuel system pressure to a third pressure which is less than said preset pressure.

Abstract: A method for operating a fuel system is disclosed. The method includes sequentially purging fuel vapors from each of a plurality of regions of a canister. Purging a region includes opening an air inlet valve associated with that region and maintaining air inlet valves associated with each other region closed to direct fuel vapors to at least one purge outlet.

Abstract: A method for desorbing fuel vapors from a canister of a vehicle having an internal combustion engine and a fuel tank includes detecting the temperature within the interior of the fuel tank using a temperature sensor positioned within the fuel tank. The canister is in fluid communication with the fuel tank and an intake manifold of the engine of the vehicle. A vapor bypass valve is positioned along a flow line between the fuel tank and the canister. The vapor bypass valve is opened if the temperature inside the fuel tank falls below a pre-determined value. The low pressure region created within the fuel tank due to fall in temperature is utilized to route ambient air along with the fuel-vapors contained within the canister, towards the fuel tank, through the opened vapor bypass valve.

Abstract: Systems and methods for internal orifice characterization in an evaporative leak check module are disclosed. In one example approach, a method comprises operating a pump to draw air from an emission control system through an orifice to obtain a reference pressure, and indicating a leak in response to pressure in the emission control system remaining above a threshold pressure while operating the pump to decrease pressure in the emission control system, where the threshold pressure is based on a coded indication and the reference pressure.

Abstract: Methods and systems for passively purging a hydrocarbon trap in an engine intake in a vehicle are disclosed. In one example approach, a method comprises, in response to an ambient temperature decrease during an engine off condition while a fuel tank is sealed from atmosphere, delivering fuel stored in a hydrocarbon trap in an intake of the engine to a fuel vapor canister coupled to the fuel tank in an emission control system.

Abstract: Methods and systems for fuel system leak detection in a hybrid electric vehicle using a fuel reservoir are disclosed. In one example approach, a method comprises, during an engine off condition, delivering fuel from a fuel tank into a reservoir while the fuel tank is vented to atmosphere, and sealing the fuel tank from atmosphere and indicating a leak based on pressure in the fuel tank.

Abstract: A method for a fuel system coupled to an engine comprising: under vacuum conditions, opening the fuel vapor canister purge valve, and generating pressure pulsations in a conduit coupled to the fuel vapor canister purge valve by opening and closing a fuel vapor canister vent valve one or more times while maintaining the fuel vapor canister purge valve open. In this way, contaminants and/or debris that may prevent the canister purge valve from closing completely may be dislodged and evacuated to the intake manifold.

Abstract: Methods and systems for fuel system leak detection using passive canister vent valves are disclosed. In one example approach, a method comprises generating engine off vacuum or pressure in a fuel system for leak diagnostics, where the pressure and vacuum are held via first and second mechanical relief valves positioned in parallel with one another and without a valve holding current.

Abstract: A method may comprise correcting an intake oxygen concentration based on fuel canister vapor purge only during boosted conditions, and adjusting exhaust gas recirculation responsive to the intake oxygen concentration.

Abstract: Systems and methods for a multi-path purging ejector are disclosed. In one example approach, a multi-path purge system for an engine comprises an ejector including a restriction, first and second inlets, and an outlet, and a shut-off valve hard-mounted to an intake of the engine and coupled to the outlet.

Abstract: A method for an engine fuel system comprises, during an engine-off condition, indicating a refueling event based on a rate of change in fuel tank pressure, and aborting a diagnostic leak detection test based on the refueling event indication. Indicating a refueling event further comprises indicating a refueling event based on the rate of change in fuel tank pressure being greater than a first threshold when the canister vent valve is open, and greater than a second threshold when the canister vent valve is closed, the first threshold being less than the second threshold.

Abstract: Methods are provided for reliving excess vacuum from a fuel tank. In response to elevated fuel tank vacuum levels, a canister purge valve is opened to dissipate the vacuum to an engine intake manifold while the engine is not combusting. Alternatively, the purge valve is opened to dissipate the excess vacuum to the intake manifold while the engine is combusting during conditions when the likelihood of air-fuel ratio errors are lower or when any incurred errors are better tolerated.

Abstract: Systems and methods for operating an engine with a fuel vapor recovery system are disclosed. In one example approach, a method comprises, during a diurnal condition, providing a first amount of venting to a fuel vapor canister, and during a purge condition, providing a second amount of venting to the fuel vapor canister, where the second amount is greater than the first amount.

Abstract: A method for a vehicle having a fuel vapor canister coupled between a fuel tank and an engine intake manifold via an electronically controlled purge valve, comprises initiating a vapor leak test under predetermined conditions and in response to said initiation, fully opening said purge valve from a closed position to a fully open position for a predetermined time, and then fully closing said purge valve after said predetermined time and commencing said leak test.