funny thing, I just ran into a simmilar problem today with my 1998 Ford Ranger 4x4.. swapped out the bad starter, which in itself is a royal PITA on that truck.. went to crank, and got a slow crank like the new starter was also bad, or the battery was dead.. so I got jumper cables, and it started. but would not start without them.. so I went and rechecked what I did, and found the ground strap that goes to the starter dangling.. put it all back togther and it's fine...