Oiler failure on these saws is almost always due to one of two causes. Either the rubber check valve in the fitting that passes crankcase pressure pulses to the oil tank is bad, or else the line in the oil tank that carries oil from the oil pick-up filter to the bar is broken. With the oil tank empty, shine a light into the tank to inspect this oil line while you touch it with something to see if it is sound. The fitting with the check valve is located just above and forward of the clutch. It can be removed with a 1/2" box end. put a piece of tubing on the threaded end and test it. Air should be allowed to pass outward toward the hex end, and it should also hold a vacuum on the threaded end. Do a search on this. I went over this in detail a couple months ago.