generator blowing things up
I have a little conundrum. I have to use my generator once in a great while, so I have my electrical box rigged to power it with a 40amp dual pole breaker that feeds the box. I kill the mains and turn on only the essentials. This time I had the generator running, registered 240v at the box. I turned on a 120v circuit and it only registered 45v. One circuit I turned on, blew the GFI plug and fried the microwave. Another fried a surge suppressor. I have done this before and it worked fine. The genny is probably 20 years old. Any thoughts?