Through the years, I have found it depends, and it has always been present since the death of leaded gas. Yep, I use to pump leaded in it cause you boys in TX were one of the last states in the union to ditch leaded gas.

Anyway, the thing that has seemed to work the best for me is to fish it in and out some, keeping upward pressure, forcing the nozzle tip down. I have also ran into particular pumps that just won't pump, but the one beside it works; solution is not to use that particular pump.