How does the whole world lose and then remain without electricity? Even if you had a global event that completely wiped out the current electrical grid. It is repairable. New homes in the US have had electricity for a hundred years.
There are hundreds of thousands of people who know how to build or repair generators. Hundreds of thousands more could do so with the help of a book.
Delicate electronic parts that control idles on generators are not required parts. They just make the engines more efficient.
I think the scenario of long time world system failure is unrealistic. IMHO
