Chainsaw Repair

no cracks in the case. I pulled the copper line and grommet away from the bar mount pad and the oil is coming out of it, not the case.
flow increases when you apply a bit of pressure through the vent. slows when you apply vacuum. no oil leaks through the vent unless you pull some through with vacuum.
ZERO oil coming through to the center (or anywhere else) of the oil pump. there are no leaks anywhere.
I would expect pressure from the cap when screwed in, but after a while of the oil being pushed out, that 'pressure' would turn to 'vacuum' if there wasn't any air getting in there. like I said, there's almost enough oil coming out to lube a small bar/chain 
even after rotating the pump backwards to empty the outer line, and removing the cap, it will still flow. and empty the tank down to about an 8th left over. the oil has to move up through the pump, and up into the discharge tube. way higher than the inlet or the level of the oil. that's the part that has me stumped. I would figure temperature changes would be the culprit, but it doesn't matter weather you have it out in the cold and bring it in to a warm room (or vice-versa) or if you put cold/warm oil in it.
the saw started doing this on him this past spring. but "fixed" it self before he had time to get a look at it. restarted doing this last week.
saw runs perfectly fine. oils perfectly fine.
the guy doesn't have a whole lot of cash, and I don't want to order a new pump to find out that wasn't the problem (I don't think it is). I also don't think it's the vent, but maybe?