When I primed my Rover V8, it took a very long time to get oil at the rockers using a drill on the pump shaft. Loosen the pressure gauge union at the gauge end and bleed the line, then you might see presure on the gauge, but don't expect much with a drill.
It might just be OK Have you tried spinning it on the starter with the plugs out?
Otherwise a small air leak in the inlet pipe,gauze in the sump could be the cause. I had this once on an Essex V6 and the oil pressure was very lazy.
