Methods and systems for determining pressure changes across at least two fuel vapor storage canisters are described. The methods and systems may include determining the pressure changes via a sole pressure sensor. In one example, fuel vapor canister bypass passages are provided to determine pressure values at a plurality of positions within an evaporative emissions system.

A failure diagnosis method and a failure diagnosis system of a dual purge system may determine whether a closed stuck failure or an opened stuck failure occurs in a line forming a dual purge system by measuring a pressure in a negative pressure formation device and comparing the corresponding pressure with a predetermined reference value when a purge valve of the dual purge system is in an opened or closed state, and may determine whether the failure occurs in components related to a secondary purge line in the dual purge system in which it is difficult to determine whether the failure occurs in a conventional failure diagnosis method of a single purge system in a simple method.

Systems for hybrid electric engines have a fuel vapor canister (FVC) in fluid communication with (i) fuel vapor in a fuel tank with a refueling valve therebetween, (ii) an intake manifold with a canister purge valve therebetween, and (iii) atmospheric pressure (atm) with a canister vent valve (CVV) therebetween, a bypass loop around the refueling valve, and a pressure sensor upstream of both the refueling valve and the CVV. The loop has a control pump and a control valve controlling fluid communication with atm, and in a first mode, control valve and CVV open, pumps fuel vapor to the FVC for pressure control, then closes the control valve; in a second mode, control valve closed and CVV open, pumps atm to the FVC; and in a third mode, control valve and CVV open, pumps fuel vapor to the FVC to a pre-selected threshold to close the CVV.

A fuel tank isolation valve for a vehicle is provided. A valve opening operation or a valve closing operation is performed using guide protrusions configured to move along a guide slot, in response to an upward or downward movement of a plunger. The discharge of a battery is prevented. An abrupt change in the pressure of a fuel tank is prevented.

Methods and systems are provided for an evaporative emissions control system for onboard refueling vapor recovery of a heavy duty vehicle. In one example, a method may include, in response to greater than a threshold change in a fuel level of a fuel tank fluidically coupled to at least two fuel vapor storage canisters of an evaporative emissions control system during a refueling event, performing a canister working capacity diagnostic on each of the at least two fuel vapor storage canisters by measuring an exhaust gas air-fuel ratio (AFR) while independently purging each of the at least two fuel vapor storage canisters. In this way, the working capacity of each fuel vapor storage canister may be separately assessed in order to more accurate identify degradation of the working capacity.

A vent shut-off assembly configured to manage venting on a fuel tank configured to deliver fuel to an internal combustion engine includes a first liquid vapor discriminator (LVD), a main housing, a first poppet valve assembly, a pump and an actuator assembly. The first LVD is disposed in the fuel tank. The main housing selectively vents to a carbon canister. The first poppet valve assembly has a first poppet valve arranged in the main housing. The pump selectively pumps liquid fuel from the main housing. The actuator assembly is at least partially housed in the main housing and includes a cam assembly having a cam shaft that includes a first cam and a second cam. The first cam has a profile that one of opens and closes the first poppet valve fluidly coupled to the first LVD.

A fuel vapor treatment apparatus includes a controller configured to detect an abnormality in at least one of a first check valve, a second check valve, a second purge passage, a charging passage, and an ejector based on pressure detected by a pressure detector.

A leak detection module (LDM) includes a housing, a canister valve solenoid (CVS) that is arranged within the housing and in fluid communication along a first fluid passageway between first and second ports. The module also includes a pump that is arranged within the housing and is in fluid communication with the first and second ports, and a pressure sensor that is in fluid communication with at least one of the first and second ports. A first controller is arranged in the housing and is in communication with the pump, the CVS and the pressure sensor. The first controller runs a test procedure using the pump and operating the CVS between open and closed positions to monitor a pressure within the module. The first controller communicates a result based upon the monitored pressure to a second controller that is arranged outside the housing and remotely from the module.

Methods and systems are provided for carrying out diagnostics of a bleed canister of an evaporative emissions control system in a vehicle. In one example, a method may include, loading the bleed canister during a refueling event, and then during an immediately subsequent engine start, detecting if the bleed canister is degraded or not based on output of an exhaust gas oxygen sensor.

Methods and systems are presented for operating a refueling valve of an evaporative emissions system. The methods and systems may attempt to reactivate a refueling valve that has stuck due to the refueling valve being exposed to liquid fuel. In one example, a voltage that is applied to the refueling valve may be increased to reactivate the refueling valve.