Abstract: Methods and systems are provided for regulating evaporative emissions from a fuel system. In one example, a method may comprise spinning an engine unfueled responsive to a hydrocarbon concentration at a fresh air end of a fuel vapor canister increasing above a first threshold. The method may comprise spinning the engine to pull hydrocarbons away until a hydrocarbon concentration at a purge end of the fuel vapor canister, opposite the fresh air end, increases above a second threshold.

Abstract: Methods and systems are provided for diagnosing a vehicle fuel system for a presence or absence of undesired evaporative emissions. In one example, a method comprises evacuating the fuel system of a vehicle to a variable vacuum target as a function of a volatility of fuel in a fuel tank positioned in the fuel system and a loading state of a fuel vapor storage canister configured for capturing and storing fuel vapors from the fuel tank. In this way, analysis of a pressure-bleedup portion of the diagnostic may be more reliable and completion rates of the diagnostic may be improved, while conducting the test in an environmentally fashion.

Abstract: Methods and systems are provided for conducting an evaporative emissions test diagnostic on a vehicle fuel system and evaporative emissions control system during engine-on conditions. In one example, a first fuel vapor storage device is separated from a second fuel vapor storage device by a one-way check valve, thus preventing loading of the first fuel vapor storage device during conditions such as refueling operations, diurnal temperature fluctuations, or from running-loss vapors from a vehicle fuel tank. In this way, the evaporative emissions test diagnostic may be conducted during a cold-start event where an exhaust catalyst is below a predetermined threshold temperature required for catalytic oxidation of hydrocarbons in the engine exhaust, without increasing undesired exhaust emissions.

Abstract: Methods and systems are provided for conducting an evaporative emissions test diagnostic on a vehicle fuel system and evaporative emissions control system during engine-on conditions. In one example, a first fuel vapor storage device is separated from a second fuel vapor storage device by a one-way check valve, thus preventing loading of the first fuel vapor storage device during conditions such as refueling operations, diurnal temperature fluctuations, or from running-loss vapors from a vehicle fuel tank. In this way, the evaporative emissions test diagnostic may be conducted during a cold-start event where an exhaust catalyst is below a predetermined threshold temperature required for catalytic oxidation of hydrocarbons in the engine exhaust, without increasing undesired exhaust emissions.

Abstract: Methods and systems are provided for conducting an evaporative emissions test diagnostic on a vehicle fuel system and evaporative emissions control system during engine-on conditions. In one example, a first fuel vapor storage device is separated from a second fuel vapor storage device by a one-way check valve, thus preventing loading of the first fuel vapor storage device during conditions such as refueling operations, diurnal temperature fluctuations, or from running-loss vapors from a vehicle fuel tank. In this way, the evaporative emissions test diagnostic may be conducted during a cold-start event where an exhaust catalyst is below a predetermined threshold temperature required for catalytic oxidation of hydrocarbons in the engine exhaust, without increasing undesired exhaust emissions.

Abstract: Methods and systems are provided for regulating evaporative emissions from a fuel system. In one example, a method may comprise spinning an engine unfueled responsive to a hydrocarbon concentration at a fresh air end of a fuel vapor canister increasing above a first threshold. The method may comprise spinning the engine to pull hydrocarbons away until a hydrocarbon concentration at a purge end of the fuel vapor canister, opposite the fresh air end, increases above a second threshold.

Abstract: Methods and systems are provided for diagnosing a vehicle fuel system for a presence or absence of undesired evaporative emissions. In one example, a method comprises evacuating the fuel system of a vehicle to a variable vacuum target as a function of a volatility of fuel in a fuel tank positioned in the fuel system and a loading state of a fuel vapor storage canister configured for capturing and storing fuel vapors from the fuel tank. In this way, analysis of a pressure-bleedup portion of the diagnostic may be more reliable and completion rates of the diagnostic may be improved, while conducting the test in an environmentally fashion.

Abstract: Methods and systems are provided for operating an evaporative emissions system in a turbocharged engine. In one example, a method may include pulsing open a canister purge valve responsive to the turbocharged engine entering a boosted mode of operation. The canister purge valve may be opened for a duration long enough to close a check valve coupled between the canister purge valve and an intake of the engine.

Abstract: A vehicle method for barometric pressure identification, including adjusting engine operation responsive to barometric pressure, the barometric pressure based on a pressure change at a sector of the fuel system when the sector is sealed with the vehicle travelling. The method may utilize a pressure change at the sealed sector of the fuel system, such as a sealed fuel tank, to identify barometric pressure, even with the engine off for extended durations of vehicle travel. As such, in a hybrid-vehicle application, including during hill descents in which the engine is maintained off, barometric pressure can still be updated.

Abstract: Methods and systems are provided for operating an evaporative emissions system in a turbocharged engine. In one example, a method may include pulsing open a canister purge valve responsive to the turbocharged engine entering a boosted mode of operation. The canister purge valve may be opened for a duration long enough to close a check valve coupled between the canister purge valve and an intake of the engine.

Abstract: A vehicle method for barometric pressure identification, including adjusting engine operation responsive to barometric pressure, the barometric pressure based on a pressure change at a sector of the fuel system when the sector is sealed with the vehicle travelling. The method may utilize a pressure change at the sealed sector of the fuel system, such as a sealed fuel tank, to identify barometric pressure, even with the engine off for extended durations of vehicle travel. As such, in a hybrid-vehicle application, including during hill descents in which the engine is maintained off, barometric pressure can still be updated.

Abstract: A vehicle method for barometric pressure identification, including adjusting engine operation responsive to barometric pressure, the barometric pressure based on a pressure change at a sector of the fuel system when the sector is sealed with the vehicle travelling. The method may utilize a pressure change at the sealed sector of the fuel system, such as a sealed fuel tank, to identify barometric pressure, even with the engine off for extended durations of vehicle travel. As such, in a hybrid-vehicle application, including during hill descents in which the engine is maintained off, barometric pressure can still be updated.

Abstract: Methods and system are provided for distinguishing fuel tank vacuum generation due to canister purge valve degradation from vacuum generation due to canister vent valve degradation. A fuel tank vacuum level is monitored after sealing the fuel tank from the atmosphere following an engine pull-down. If there is an ensuing change in fuel tank vacuum, canister purge valve degradation is determined, else, canister vent valve degradation is determined.

Abstract: Methods and systems are provided for enhancing purge flow when applying shallow intake manifold vacuum. An alternate purge route that circumvents the more restrictive canister purge valve and directs purge vapors through a branched path via a less restrictive mechanical purge valve is used during low intake manifold vacuum conditions. By enabling higher purge flow rates when manifold vacuum is lower, a more complete canister cleaning is ensured.

Abstract: Methods and systems are provided for conducting an evaporative emissions test diagnostic on a vehicle fuel system and evaporative emissions control system during engine-on conditions. In one example, a first fuel vapor storage device is separated from a second fuel vapor storage device by a one-way check valve, thus preventing loading of the first fuel vapor storage device during conditions such as refueling operations, diurnal temperature fluctuations, or from running-loss vapors from a vehicle fuel tank. In this way, the evaporative emissions test diagnostic may be conducted during a cold-start event where an exhaust catalyst is below a predetermined threshold temperature required for catalytic oxidation of hydrocarbons in the engine exhaust, without increasing undesired exhaust emissions.

Abstract: Methods and systems are provided for regulating evaporative emissions from a fuel system. In one example, a method may comprise spinning an engine unfueled responsive to a hydrocarbon concentration at a fresh air end of a fuel vapor canister increasing above a first threshold. The method may comprise spinning the engine to pull hydrocarbons away until a hydrocarbon concentration at a purge end of the fuel vapor canister, opposite the fresh air end, increases above a second threshold.

Abstract: Methods and systems are provided for controlling the purging of a fuel vapor canister coupled to a vehicle fuel tank, configured for capturing and storing vapors emanating from the tank. In one example, two canister purge valves are coupled in series in a fuel vapor conduit between the fuel vapor canister and engine intake, one at the intake manifold and one at the fuel vapor canister, such that fine control over the introduction of fuel vapors into the engine is maintained via the purge valve at the intake manifold, while thorough purging of the fuel vapor canister may be regulated via the purge valve at the fuel vapor canister. In this way, fuel vapors in the fuel vapor canister may be effectively purged to intake, thus reducing the potential for undesired evaporative emissions.

Abstract: Methods and systems for controlling and reducing current consumption of a vapor blocking valve are disclosed. In one example, current supplied to the vapor blocking valve is adjusted proportionately to fuel tank pressure to compensate for fuel tank pressure acting on the vapor blocking valve. Vapor blocking valve current is adjusted to reduce current consumption.

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 controlling the purging of a fuel vapor canister coupled to a vehicle fuel tank, configured for capturing and storing vapors emanating from the tank. In one example, two canister purge valves are coupled in series in a fuel vapor conduit between the fuel vapor canister and engine intake, one at the intake manifold and one at the fuel vapor canister, such that fine control over the introduction of fuel vapors into the engine is maintained via the purge valve at the intake manifold, while thorough purging of the fuel vapor canister may be regulated via the purge valve at the fuel vapor canister. In this way, fuel vapors in the fuel vapor canister may be effectively purged to intake, thus reducing the potential for undesired evaporative emissions.