It's been a while, but I thought you could boot without the 8-pin, if you only had one processor installed. Am I mis-remembering?
OK, folks, out of desperation I purchased a new power distribution board and installed it. Problem solved - s5000PAL has clean power and POSTs just fine.
My hair is starting to grow back now...
Power Distribution Boards are NOT cheap...
Not sure if 8-pin power is needed to boot and POST...I just replaced the PDU out of desperation and the system booted up clean.