Have a Pioneer Farmsaw that stopped oiling so I took it apart and found a broken oil supply line. Cleaned up the pump, replaced the line and everything looked good so put it all back together. I thought I would test it while it was still on the bench so I pulled the plug and attached an electric drill to the clutch and spun the engine over. No oil appeared. Thinking this is an old saw with MANY hours on it, maybe there was just enough wear in the pump to prevent it from developing enough suction to pull the heavy weight summer oil up the supply tube, so I found a cork that fit the oil tank filler hole, drilled a hole in it and installed a fitting that would let me pressurize the tank with my crankcase tester. A little pressure in the tank and a little more spinning with drill and the oiler started to work and continues to do so. Wish every oiling problem was this easy to solve.
