A vehicle fuel system is provided that includes a fuel tank and a manual vent system. The manual vent system includes an emergency valve and an actuator. The manual vent system is configured to cause the emergency valve to open after the actuator has been actuated.

A method is presented wherein during a first condition that includes a fuel tank pressure above a threshold, a fuel tank is fluidically coupled to a fuel vapor canister while a fuel vapor canister vent path is restricted, and a degree of restriction of the fuel vapor canister vent path is modulated. Modulating the degree of restriction of the fuel vapor canister vent path allows a fuel tank to be depressurized at a controlled rate. In this way, excess fuel tank pressure can be relieved, even if a vehicle engine is not operating in a combustion mode.

A method for a fuel system, comprising: during a first condition, purging fuel vapor from a fuel vapor canister to a fuel vapor accumulator; and then during a second condition, evacuating fuel vapor from the fuel vapor accumulator to a fuel tank. The fuel vapor accumulator increases the volume of the fuel system, providing a temporary storage for desorbed fuel vapor. In this way, canister breakthrough of hydrocarbons can be mitigated, thereby reducing bleed emissions.

Methods and systems are provided for a fuel system. In one example, a fuel system includes a plurality of canisters with a fuel tank isolation valve (FTIV) configured to control a fluid coupling between each of the plurality of canisters and a fuel tank. The FTIV is actuated based on one or more of a fuel tank pressure and a load of each of the plurality of canisters.

A fuel evaporative emission processing system suitable for a hybrid vehicle includes a fuel vapor passage, a shut-off valve, a purge passage, a first purge control valve, and a second purge control valve. The shut-off valve selectively opens and closes the fuel vapor passage communicating between a fuel tank and a canister. The first purge control valve opens and closes the purge passage communicating between the canister and an intake air passage of an internal combustion engine. The second purge control valve selectively opens or closes the tank opening passage communicating between the purge passage on an upstream side of the first purge control valve and the fuel tank. When purging the canister, by opening the second purge control valve, the evaporative fuel inside the fuel tank is directly processed by the internal combustion engine, so that increase in the amount of adsorption in the canister can be suppressed.

Methods and systems are provided for a fuel system. In one example, a fuel system includes a plurality of canisters with a fuel tank isolation valve (FTIV) configured to control a fluid coupling between each of the plurality of canisters and a fuel tank. The FTIV is actuated based on one or more of a fuel tank pressure and a load of each of the plurality of canisters.

In one embodiment, a valve assembly for a liquid tank system includes a valve housing and a cover. The valve assembly includes an orifice frame structure defining an orifice in a first shape therethrough, and a ribbon having a movable end. The ribbon is configured to seal or unseal the orifice along a first axis of the orifice when the movable end of the ribbon moves with the float. The orifice is asymmetrical across a second axis perpendicular to the first axis and passing through a middle point of the orifice. A first area of the orifice on a first side of the second axis is smaller than a second area of the orifice on the second side of the second axis. The first area of the orifice is configured to be unsealed earlier than the second area of the orifice by the ribbon.