Ok, I have an old Campbell hausfield compressor I've been using in my garage for years. Last winter I decided to change the oil. I drained it and replaced with 30 wt motor oil, at the time that's all I had. After that, it puked a lot of oil out of a breather. Since then, when cold it starts right up but once it shuts itself off and the pressure drops enough to kick it on, the pump won't turn over, the belt doesn't slip, it stalls the motor and eventually throws the breaker. I can get it to start by manually turning the driven pully backwards to give the motor more of a running start at the compression stroke, otherwise it doesn't run.
Tried draining the oil and replacing with actual compressor oil yesterday, no change. Thought maybe too much oil, so I drained it in increments and tried to start it. Nothing. Let out all the oil and still no start.
Any ideas?