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.