A few of my older SCSI drives have done this, started spinning up and then stopped. This unfortunately signals that the drive is dead and there's no real way to fix it.

I would suggest going along the lines of looking for 50 to 68 pin adaptors and getting hold of some more modern 68 pin SCSI drives. This has worked well for me so far and the newer SCSI drives tend to be a lot faster and more reliable.