Fuel pump prime

Just got 415C, ser# 505 out of annual. It seems like each time I do there's a problem with re-establishing fuel pump pressure to header tank. The top is taken off the pump each year to comply with the AD that requires the expensive little kit that replaces the filter screen and gaskets. Then, when I get it back from the mechanic, it won't fill the header tank. I've had the plane for 3 years now and have fixed it by different means in the past. Tightening the bolt that holds the dome of the pump on a little more than spec. Re-seating the dome to make sure there's a good seal to the pump body. This year, I can't seem to make it work. When I remove the dome and put a little fuel in the cylinder inside that leads to the pump diaphragm and then to the outflow line (to the header tank) and turn the prop, it sucks the fuel down like it should so I know the diaphragm is working. The fuel valve under the passenger seat is on. Both wing tanks are full.

Frustrated.

Chris
Sioux Falls, SD
Ser #505