System and methods for fuel system recirculation tube diagnostic

A method comprising:

• responsive to a fuel tank fill level below a first threshold, applying vacuum to a fuel system to generate a first fuel system pressure profile;
• responsive to a fuel tank fill level above a second threshold, applying vacuum to the fuel system to generate a second fuel system pressure profile;
• and
• indicating a restriction in a vapor recirculation line based on the first and second fuel system pressure profiles, wherein:
• a fuel tank is coupled in the fuel system within a vehicle, wherein the pressure profiles are pressure profiles over time, and wherein the fuel tank is coupled to a fuel filler neck via a spud valve, the fuel filler neck coupled to a negative pressure relief valve;
• taking an action in response to the indicated restriction;
• and
• wherein the first threshold comprises a fuel level below the spud valve, and wherein the second threshold comprises a fuel level above the spud valve, wherein the fuel tank fill level below the first threshold comprises a first condition and the fuel tank fill level above the second threshold comprises a second, different, condition, wherein none of the pressure profile of the first condition overlaps a duration of the pressure profile of the second condition.