Pulled fuel pump and observed some scratches in the raised lips that sandwich the diaphragm between the two halves of the pump. I put a piece of sandpaper on the
bench and used a twisting motion to resurface the two halves. Reinstalled pump and problem solved. I think one or more of those scratches might have been enough
to let just a little gas through and then spit out that hole. Oil seems to be ok but I'm going to change it anyway. Oil is cheap- engines are expensive.