[Mike C]

I completely flushed the tank when we took the truck apart. The two 5/16 lines for the charcoal cannister are clear. The 1/2" vent to the filler is not... I could not push a coat hanger through it. I put a vacuum on it and nothing. I sealed up everything else on the tank and put 90 psi of air on one of the 5/16 lines. It caused the tank to expand and then pushed fuel out the filler neck. I soaked it in Seafoam before this.

It is completely and perfectly 100 % blocked. In the mean time I have routed the filler neck vent to one of the 5/16 nipples. My brand new fuel sender failed after the first full tank of fuel so the tank has to come out again. I will investigate more at that point. If I cannot get that one to vent I will tee the two 5/16 into the 1/2 vent line.