The problem does not have to be the O-ring. But to begin with that since it was something you last touched, are you sure it was the oil pump O-ring you installed? The is another O-ring that is very close. I think it's the cylinder base O-ring but it might be the flywheel spacer O-ring. One of them is sometimes mistaken for the oil pump O-ring.
I don't think you should start there. How about the oil pressure regulating valve, This is part of the front bearing holder that is under the timing chain crank sprocket. A broken spring in this will cause oil pressure problems. You have to remove the timing cover to look at it. They do go bad.
There is also a bypass valve in the oil filter canister area. It is at the back of where the filter is. Remove filter and look at the back, you should see a ball check valve. Is the ball in place? Can you push it in a tiny amount with a skinny screwdriver and it pops back out into place?
disston screwed with this post 06-17-2013 at 08:29 AM