Long story short, standard eng. shut-down, main fuel pump switch to OFF, half second or less, eng. quits rather quickly. """UNLESS""" you are low on fuel,,, & picked up some air in the lines,,, eng. remained running,,, after shaking the thoughts of gremlins out of my head, possible as long as 20-30 seconds & quick look at fuel gauge for tank I was on the thought came to me that I picked up air from empty tank & pressurized it with fuel pump, I now have an air pressure-fuel pump backup sys. so eng. will remain running, had to shut down elect. to stop eng. How about that one to start the year. David R. Cook RV6A Rotary.