Don, I think you are right that the
oil pump in itself would prevent backflow WHILE it is pumping (ie when the motor is running). However, as a pre-oilier, before starting the motor, the pump would not be running and therefore not in itself, be able to stop backflow.
But as you pointed out, backflow will be prevented by the design of the
oil filter. (If you accidentally switch of
oil lines going in and out of the oil filter you will get virtually no oil pressure because of that design!)
When I spoke with the folks at Canton/Accusump, tel# (203) 481-9460, they told me that it makes all most no difference at all if you use a check valve or not. They also faxed me the full copy of the Accusump installation and owners manual. It did show several different set ups. I would suggest that you too might ask them to fax you a copy.
Okiesnake