I was using a 3930 the other day to unload a welder from a truck and I wasn't thinking to clearly (hard day before). I was cutting the diesel on and off while positioning and connecting chains, etc. Two times when I started it, it made a loud snap-bang(sounding like bad things happening inside the engine)and began blowing white and blue smoke for the first time. Scared the he!! out of me. Then I let it warm up and drove it to it's parking space and shut it down. Sometime later I started it again and all was fine , no bangs and normal smoke. What happened here?