magnaflow
I had a brand new Aeromotive 2000 that blew fuses out of the box. I checked the motor for continuity and it was good and it did not show a ground. So I took it apart and found nothing really wrong, but the impeller was stuck to the bottom plate. It came right loose and after I just cleaned it up inside and lubed it, it has run fine since.
After I was putting it back together I noticed I probably could have accessed the impeller from the ports and just freeded it up without taking it apart.