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 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 determining an extent of clogging of a canister filter included in a fuel vapor storage canister of a vehicle. In one example, a method comprises determining an extent to which the canister filter is clogged based on an output of an exhaust gas sensor, and adjusting one or more parameters related to purging of the fuel vapor storage canister as a function of the extent to which the canister filter is clogged. In this way, canister lifetime may be improved, and release of undesired evaporative emissions to atmosphere may be reduced or avoided.

A fuel system in particular of a motor vehicle, includes a fuel tank and a ventilation device for ventilating the fuel tank. The ventilation device has at least one separation device which has a temporary accumulator for liquid fuel. The separation device is made at least in part of a porous material and/or is filled with the porous material.

A method for an engine is presented, comprising, following an engine-off event, positioning a first engine cylinder with an intake valve open, opening a canister purge valve; and purging contents of the first engine cylinder to a fuel vapor canister. In this way, uncombusted fuel that may otherwise be emitted from the engine during a prolonged diurnal soak may be stored within the fuel vapor canister, thus decreasing overall vehicle emissions.

An active purge pump system module is provided for an evaporative emission control (EVAP) system for a vehicle. The EVAP system includes a fuel tank, a vapor collection canister in communication with the fuel tank, an air intake, and a purge valve connected between the canister and the air intake. The active purge pump system module includes a pump in fluid communication with the canister to move air independently of operation of the engine. A bypass valve assembly communicates with an upstream side and a downstream side of the pump to bypass the pump. In a closed position of the bypass valve assembly, the pump, when activated, moves purge vapor from the canister, through the purge valve, and to the engine to be consumed during combustion, and when the bypass valve assembly is opened and the pump is deactivated, vehicle refueling is permitted.

In a VST (vapor separator tank), a lower case is provided with a plurality of attachment portions attached to an engine (internal combustion engine) and drain piping for discharging liquid fuel from a fuel storage compartment. The lower case includes a first bottom surface portion including a lowermost surface, a second bottom surface portion formed in a position higher than the first bottom surface portion and supporting a pump, and a third bottom surface portion formed in a position higher than the first bottom surface portion and the second bottom surface portion. Disclosed embodiments provide a vapor separator tank in which the capacity of a fuel storage compartment is sufficiently secured, and which allows easy arrangement of other equipment and parts around the vapor separator tank while enabling easy design change.