Mike, thanks for playing.. the Gex pump has a "wet" end and a "dry" end.. the magnet spins on the outside of the of the wet end turning the impeler inside... the autotop off was one of my first thoughts but it was fine..
next clue : you are diagnosing the correct side of the pump as evidenced from my above comments.. ar is being sucked in from the negative pressure side. these are the components,, a heavy duty bulkead, two threaded connections, a ball valve and a coupling.