Methods and systems are provided for diagnosing degradation in a variable volume device included within a pressure-less fuel tank. In one example, a method may include, upon conditions being met, operating a pump of an evaporative emissions control (EVAP) system leak detection module (ELCM) to evacuate the variable volume device. A degradation of the variable volume device may be indicated based on a change in pressure at the variable volume device.

A vehicle system includes a fuel separation system, a combustion engine, and a computer control system. The fuel separation system includes one or more fuel separation units, the vehicle system is configured to recover from the fuel separation system and maintain vapor fuel fractions as vapor throughout the vehicle system, and the combustion engine is configured to receive a vapor fuel feed and a liquid fuel feed. A method for operating the vehicle system includes separating a vehicle fuel with a fuel separation system into a plurality of fuel fractions, recovering and maintaining the vapor fuel fractions as vapor throughout the vehicle system, producing a vapor fuel feed and a liquid fuel feed, and introducing at least one of the vapor fuel feed and the liquid fuel feed to a combustion engine.

An evaporated fuel processing device that includes a pressurizing pump configured to pressurize gas in the vapor passage downstream of the closing valve toward the closing valve; a first pressure sensor configured to detect a pressure in the fuel tank directly or indirectly, and/or a second pressure sensor configured to detect a pressure in the vapor passage downstream of the closing valve directly or indirectly. When the closing valve moves toward an open side in the closed state with the pressurizing pump pressurizing the gas in the vapor passage downstream of the closing valve toward the closing valve, the controller may specify a valve-opening-start position based on the pressure detected by the first pressure sensor and/or the pressure detected by the second pressure sensor, wherein the valve-opening-start position is a position where the closing valve transitions from the closed state to the opened state.

Methods and systems are provided for diagnostics of a fuel system configured with a three-way isolation valve and a four port canister. An example method includes, during a refueling event, indicating degradation of the three-way isolation valve based on pressure in the fuel tank during depressurization followed by refueling.

There is provided a valve device, including: a housing in which, via a partition wall, a valve chamber is provided below the partition wall and a vent chamber is provided above the partition wall, and a vent hole through which the valve chamber and the vent chamber communicate with each other is provided in the partition wall; and a float valve. A valve seat is formed on a side of the valve chamber of the partition wall, and an opening is provided on an inner side of the valve seat. The opening includes a first opening and a second opening extending outward in a slit shape from an outer periphery of the first opening. A seal part having elasticity that contacts with and separates from the valve seat to close and open the first opening and the second opening, is disposed above the float valve.

A failure diagnostic device is configured to determine saturated vapor pressures of a fuel within a fuel tank. In a fuel vapor processing apparatus, some or all of the passages and spaces into which the fuel vapor flows into the fuel vapor processing apparatus are closed to the atmosphere. In this condition, the failure diagnostic device determines a plurality of saturated vapor pressure characteristics over time. The failure diagnostic device is configured to diagnose whether or not a leakage or a blockage failure in the fuel vapor processing apparatus is present. The failure diagnostic device determines a Reid vapor pressure (RVP) based on each of the plurality of determined saturated fuel vapor pressure characteristic and diagnoses whether or not a failure is present in accordance with a change in these RVPs over time.

A leakage detector for a fuel vapor treatment device includes a fuel vapor treatment device that maintains the interior of a treatment system of the fuel vapor treatment device in a sealed state. In addition, the leakage detector includes; a closing valve and shutoff valve that can shut off fluid communication between the fuel tank and the canister to section the interior of the treatment system into a first region including the fuel tank and a second region including the canister. Further, the leakage detector includes an aspirator that applies a negative pressure to the second region. The leakage detector for the fuel vapor treatment device determines the presence and/or absence of leakage in the first region on the basis of a change in the pressure in the first region while an engine is stopped and determines the presence and/or absence of leakage in the second region on the basis of a change in the pressure in the second region by applying a negative pressure to the second region while the engine is operated.

A purge control unit opens the purge control valve to supply, as purge gas to an intake passage, the evaporative fuel together with air in response to a predetermined purge request. An air-fuel ratio detection unit detects an air-fuel ratio of the internal combustion engine. A concentration learning unit estimates a fuel concentration in the purge gas based on a change in the air-fuel ratio when the purge control unit causes the purge gas to be supplied to the intake passage and to perform a fuel concentration learning to update a concentration learning value, which is a learning value of the fuel concentration in the purge gas, based on the estimated fuel concentration. An injection control unit corrects a fuel injection amount based on the concentration learning value in a period in which the concentration learning unit performs the fuel concentration learning in the lean combustion operation.

Methods and systems for performing diagnostics on an evaporative emission are described. The methods and systems may include evaluating pressure or vacuum development within an evaporative emissions system over time to determine the presence or absence of a breach in the evaporative emissions system. If a breach is identified, mitigating actions may be performed.

A method actuates a dosing valve of a tank ventilation system. The dosing valve is opened not only once but twice at every activation time, and thus a generated pressure wave is depleted. An associated tank ventilation system and an associated motor vehicle make use of the method.