Don't know if this helps, and it may be a long shot, but I'll throw it out there.
I have known of condensation build-up in gas tanks to a point where there's enough water to block the lines. In cold snaps, the water can even freeze in the lines.
Regular use of gas line antifreeze, or just mostly keeping the tank fairly full can usually prevent this.
Simple, but a long shot. . .
Otherwise you're probably looking at something fairly complicated . . .
and possibly fairly expensive.