Patent attributes
Methods and systems are provided for indicating restrictions in a fuel system vapor recirculation line. In one example, a fuel tank is evacuated responsive to a fuel level below a threshold, and if the vacuum is relieved via a negative pressure relief valve in a capless fuel filler system, the negative pressure relief valve is indicated to be functional such that, responsive to a fuel level greater than a threshold, the fuel system may be evacuated and a restriction may be indicated in the vapor recirculation line responsive to the negative pressure valve not relieving the applied vacuum. In this way, restrictions in the vapor recirculation line may be rapidly diagnosed and excessive loading of a fuel vapor canister may be prevented, thus reducing the potential for evaporative emissions being released to the atmosphere and prolonging fuel vapor canister function.
