Hello Kurt,
Even tho you have the main elec switch off, still check to see if there is any current still going to the pump. Maybe there is a smash, burnt or crossed wired still sending current to the pump. It could also be a very small current just enough to be there but not enough to turn the blades. Kinarfi, think that could do it?
Check and make sure your ground straps on the trans & engine are clean & tight.
rocmoc n AZ/MX