I never suspected a problem with the line between the pulse pump and the carb. Having a blocked PRESSURIZED line is highly unlikely. It is far more probable that the vacuum (pulse) line to the engine would have blockage or is pinched. This would cause a weak pulse that may not allow fuel to be pumped at cranking speed, but after running would pump enough fuel.
It is also possible that a defective fuel pump would cause the same problem.
Again, My advise is to rig up a gravity feed to the carb.
If your engine runs well, has good power, idles well, etc. It isn't going to be a carb problem.