Problems with wiring and starter.

My 1979 el camino is just about finished being restored. This is the first time in about a year and a half that we have tried to start it. When we tired to start it the starter kept turning over and wouldnt quit. We had to disconnet the battary to get it to quit. When we hook the battary back up it does not continue to turn. Whe have bench tested the starter and it seems to work fine. What could be my problem.