Anan Gen. III not working

Onan generators are used in many RVs and have a pretty good record. Yours is probably 4000 Watts. Most problems come from old fuel left sitting in their carburetors and gumming up the works. Some people have had good luck using Sea Foam to get the carburetor working and some have had to get a new carburetor. Another possibility on a vehicle that old is the rubber gas line to the generator may have cracked and is letting air into the line. Older rubber lines don't hold up as well with the alcohol in modern gas. You also have to have 1/2 tank of gas. Generators draw from the top of the fuel so you can't run out of gas while camped. Never try to run the generator while plugged into shore power. You could feed back to the lines and kill a lineman if he is working on a dead line. Transfer switches should eliminate that but anything can fail once.