A picture of the filter would help. As a rule there was a very small hole in the center pipe. It was small to keep the filter from reducing the oil pressure in the engine. It may be plugged with sediment to the point it's not visible. You might try blowing compressed air through the return line. That should dislodge any plug in the pipe. If the return line is connected to the pipe there has to be a hole there somewhere.

@tiny I didn't think of capping one end and blowing air through it. <smacks own forehead>.  

That worked.  Plugged off the outlet port on the bottom, blew air through the top.  The hole is an inch or two from the top, on the passenger side where I couldn't otherwise see it.  Didn't measure it, but maybe 1/8" dia. 

Thank you!

1/8" sounds a bit big to me. They usually are a bit smaller than that. When the oil is full hot it's very thin so you don't want something robbing oil pressure from the engine. If it's the factory hole it's probably OK. Just don't make it bigger thinking you're improving it.

@tiny My guess was just that... I have no doubt it's original.  Thank you!