That oil pump can be a real pain in the buttocks .I must have had the one in my Mac 1000 in and out a half dozen times before it worked .Changed the pick up line ,had the check valves apart ,new o-ring .Frustrated the hell out of me .Then an idea,prime the damned thing through the plug in the front of the pump.Blew enough oil to lube a 42 " bar .
One thing I did notice was the shaft and worm always had a little bit of oil on it every time I removed it .It appears to me it might be designed to weep just a tiny bit of oil down the shaft to lubricate the gear train .Something like the axle of a 3/4 and larger pick up truck lubricates the axle bearing .It would make sense there might not be enough lubrication from the oil in the fuel mix to properly lubricate a metal gear train.
At any rate it doesn't blow smoke like it has a crankcase full of oil .Oh there might be just a little wisp on a cold start but that goes away in a short .Not a big deal .