I have been doing some extensive reading on this forum, as well as any other source I can get my hands on, on the problems with surging and shutting down of Onan generators, and it seems that a lot of folks seems to be experiencing similar issues recently. While not all shutdowns and surging events share the same symptons and diagnosis, one common theme that they seem to share is heat and or vapor lock, however, these latter causes have not been guaranteed as definitely being the culprits. Do a search here and you will find many suggestions for curing this, but so far, I have not heard of a magic bullet for what ails a great number of Onan generators. In my case, I replaced the fuel filter, air filter, all rubber fuel lines, and moved the fuel pump outside and away from the generator. I am still waiting to see if the problem has gone away. During you research, you will find suggestions which range from the low oil sensor, float sticking in the carburetor, dirty carburetor, dirty air filter, low oil level, etc. One common theme is that those owners who have experienced the shut downs and what they believe to be vapor lock, are mostly living in extremely hot sections of the country, like Arizona. I have yet to hear this happening in winter, in Montana, or similar climates, but I could be wrong.