Methods and systems are provided for conducting a diagnostic on a fuel tank isolation valve that regulates a flow of fuel vapors from a fuel tank to an evaporative emissions system. In one example, a method comprises determining whether the fuel tank isolation valve is stuck in a first open position or a second open position based on a time duration between commanding open a canister purge valve to direct fuel vapors to an engine, and an exhaust gas sensor indicating a rich air-fuel ratio. In this way, appropriate mitigating action may be taken in response to the fuel tank isolation valve being stuck in either the first open position or the second open position.

An internal combustion engine has a tank ventilation system and a crankcase ventilation system. The tank ventilation system is connectable to an intake system downstream of a throttle element via a first non-return valve in a first line and upstream of a compressor via a second non-return valve in a second line and a third non-return valve in a second sub-line. The crankcase ventilation system is connectable to the intake system downstream of the throttle element via a fourth non-return valve in a third line and upstream of the compressor via a fourth line and the third non-return valve. The intake system is connectable to the second line downstream of the throttle element at a transitional point between the second line and the second sub-line via a fifth nonreturn valve in a fifth line. A nozzle is formed at the transitional point from the fifth line to the second line and the second sub-line, and the second line opens into the nozzle downstream of the second non-return valve. A first pressure sensor for measuring the pressure in the second line is provided in the second line between the second non-return valve and the nozzle. Only a single pressure sensor is required to diagnose or detect a leak.

A vaporized fuel treatment device includes a sealing valve disposed in a vapor passage between a fuel tank and a canister. An ECU is programmed to decrease an internal pressure of the fuel tank by a pump via the canister so as to diagnose whether leakage occurs in the vapor passage in a state where the communication between the canister and the atmosphere is cut off and the sealing valve is opened. The ECU is programmed to execute a learning of a valve opening start position of the sealing valve based on a change in the internal pressure of the fuel tank when changing an axial distance between valve element and a valve seat when the internal pressure of the fuel tank is equal to or smaller than a predetermined value after a diagnosis of leakage in the vapor passage.

Methods and systems are provided for an evaporative emissions system diagnostic. In one example, a method may include adjusting a controller operation in response to a fuel tank volume. A vehicle may determine sunrise and sunset times via a wireless modem and may relay the sunrise and sunset times to other vehicles within a threshold distance.

A system for testing an evaporative emissions (EVAP) canister of a vehicle according to the present disclosure includes an evaporator configured to contain liquid fuel, a fuel vapor supply line configured to deliver a mixture of fuel vapor and carrier gas from the evaporator to the EVAP canister, and a fuel vapor supply valve disposed in the fuel vapor supply line. The test system further includes a gas density meter configured to measure a density of the fuel vapor mixture flowing through the fuel vapor supply line, and a valve control module configured to control a position of the fuel vapor supply valve to adjust a flow of fuel vapor from the evaporator to the EVAP canister based on the fuel vapor mixture density.

A method for diagnosing a fault situation of a negative-pressure generation line using a fuel tank pressure sensor that detects the pressure of a fuel tank is provided. The method detects pressure in a fuel tank measured by a fuel tank pressure sensor when a turbocharger is operated for boosting and a purge valve is operated and diagnoses a current situation as a fault situation in which an engine negative-pressure generation line remains open when a pressure change value calculated based on the pressure difference of the fuel tank exceeds a reference value. A warning of a fault situation is then output when a fault is determined.

Methods and systems are provided for conducting a diagnostic on a fuel tank isolation valve that regulates a flow of fuel vapors from a fuel tank to an evaporative emissions system. In one example, a method comprises determining whether the fuel tank isolation valve is stuck in a first open position or a second open position based on a time duration between commanding open a canister purge valve to direct fuel vapors to an engine, and an exhaust gas sensor indicating a rich air-fuel ratio. In this way, appropriate mitigating action may be taken in response to the fuel tank isolation valve being stuck in either the first open position or the second open position.

Methods and systems are provided for reducing or avoiding engine hesitation and/or stall during engine idle conditions. In one example, a method may include inferring an engine idle condition, and in response, controlling a speed of an engine to a compensated engine idle speed that is a function of an extent to which a canister purge valve that regulates an amount of fluid flow to the engine from a fuel system and/or an evaporative emissions system, is degraded. In this way, an amount of fuel utilized to compensate for the degraded canister purge valve may be proportionate to the extent to which the canister purge valve is degraded.

Methods and systems are provided for reducing or avoiding engine hesitation and/or stall during engine idle conditions. In one example, a method may include inferring an engine idle condition, and in response, controlling a speed of an engine to a compensated engine idle speed that is a function of an extent to which a canister purge valve that regulates an amount of fluid flow to the engine from a fuel system and/or an evaporative emissions system, is degraded. In this way, an amount of fuel utilized to compensate for the degraded canister purge valve may be proportionate to the extent to which the canister purge valve is degraded.

A method for diagnosing leakage of a fuel vapor dual purge system is provided. The method includes determining whether an operation region of a vehicle is an operation region in which a turbocharger is operated and adjusting a flow amount of intake air flowing into the turbocharger according to an operation region in which the turbocharger is operated. A hydrocarbon collecting amount of a canister connecting fuel vapor generated in the fuel tank is calculated and a flow amount of the fuel vapor passing first and second purge lines is adjusted. A leak of the fuel vapor is diagnosed in the first purge line and the second purge line.