A diagnostic device is configured to execute a first acquisition process of acquiring a remaining amount of evaporated fuel in a fuel tank when an ignition switch turns off, as an end remaining amount, a determination process of, after the first acquisition process, determining whether there is a blockage of a vapor passage by reducing a pressure in a vapor passage with a pressure reducing pump when the end remaining amount is smaller than a prescribed value while the ignition switch is off, a second acquisition process of, after the determination process, acquiring a remaining amount of liquid fuel in the fuel tank when the ignition switch turns on, as a start remaining amount, and an invalidation process of invalidating a determination result that a blockage is present in the vapor passage in the determination process when the start remaining amount is larger than or equal to a set value.

A gas-leak-detection device for detecting a gas leakage from an evaporative emission system includes an electric-wire-connection portion and a passage connection portion that are disposed to overlap with at least one of appearance components in a vehicle when the vehicle is seen in a viewing direction, and are disposed closer to the at least one appearance component than a center plane perpendicular to the viewing direction when the vehicle is in an upright state, the center plane being one of an imaginary-lateral-center plane that is an imaginary vertical plane perpendicular to the left-right direction, an imaginary-longitudinal-center plane that is an imaginary vertical plane including a center in the front-rear direction and being perpendicular to the front-rear direction, or an imaginary-vertical-center plane that is an imaginary horizontal plane including a center in the top-bottom direction and being perpendicular to the top-bottom direction.

A controller is configured to execute an emission process of, on condition that the number of times a leakage diagnosis of a fuel tank is performed in a stop period from when an internal combustion engine stops to when the engine restarts is less than a predetermined allowable number of times, emitting gas from the fuel tank via a canister by opening a shut-off valve, execute a diagnosis process of performing the leakage diagnosis based on a change in index value, caused by the emission process, the index value indicating a pressure in the fuel tank, and execute a subtraction process of, when fuel has been fed to the fuel tank in a state where the shut-off valve is open in the stop period of the internal combustion engine, reducing the allowable number of times in the stop period in which fuel has been fed to the fuel tank.

Methods and systems for diagnosing operation of an evaporative emissions system are described. The methods and systems may include increasing an amount of vacuum stored in an evaporative emissions system during discontinuously operating an engine in a boosted operating mode. Storing vacuum allows the evaporative emissions system to reach a desired vacuum level to verify absence of an evaporative emissions system breech.

Disclosed is a device for evaporating vapors of a fuel stored in a motor vehicle tank. The evaporation device includes a bypass circuit and a bypass valve configured to move between a so-called “absorption” position, in which the bypass valve allows the gases to flow between the tank and an absorbent filter and a so-called “leak detection” position, in which the bypass valve allows the gases to flow between a purge circuit and the tank via the bypass circuit.

A method and device for diagnosing a leak in an evaporation system and in a tank ventilation line of an internal combustion engine is disclosed. The method includes diagnosing the entire evaporation system using a fresh-air shut-off valve of the evaporation system and a pressure sensor system of the evaporation system. During the check on whether there is a leak in the evaporation system of the internal combustion engine, a separate check of different diagnosis regions of the evaporation system is undertaken, where one of these diagnosis regions is a tank region of the internal combustion engine and a further diagnosis region is a filter region of the internal combustion engine. During the diagnosis of the tank ventilation line, the flow through the tank ventilation line is checked.

Methods and systems are provided for estimating fuel volatility. During a vehicle-off condition following a refueling event, fuel volatility may be estimated by operating a fuel pump of a fuel system immediately after the refueling event while a fuel tank temperature is stable. Based on estimated fuel volatility, fuel injection amount and leak test thresholds may be adjusted.

A method for controlling an engine for a vehicle to ensure a stable driving state of the engine on an electrical failure of a Purge Control Solenoid Valve (PCSV) may include determining, by a controller, whether a situation of an electrical failure where an opening state of the Purge Control Solenoid Valve (PCSV) is held is detected, increasing, by the controller, a failure detecting counter to a first reference value according to a state where the situation of the electrical failure of the PCSV has been detected is kept as a result of performing the failure detecting, and compensating, by the controller, a rotation number of the engine to increase the rotation number of the engine when the failure detecting counter exceeds the first reference value as a result of performing the increasing.

Methods and systems for diagnosing operation of an evaporative emissions system are described. The methods and systems may include increasing an amount of vacuum stored in an evaporative emissions system during discontinuously operating an engine in a boosted operating mode. Storing vacuum allows the evaporative emissions system to reach a desired vacuum level to verify absence of an evaporative emissions system breech.

Methods and systems are provided for conducting a test for undesired evaporative emissions in a vehicle fuel system and evaporative emissions control system based on diurnal temperature fluctuations. In one example, a method includes maintaining a vehicle controller in a sleep mode, where a sunrise or sunset event as sensed by a solar cell configured on an external surface of the vehicle triggers the controller to an awake mode whereupon the test for undesired evaporative emissions is conducted. In this way, in use monitoring performance completion rates may be improved, undesired evaporative emissions may be reduced, and the test for undesired evaporative emissions may be conducted during both heat gains and heat losses during a diurnal cycle without negatively impacting the main battery supply.