Here is a short video of the open neutral that can exist on some portable generators. Without the NG plug, my splendide washer/dryer and dishwasher would not run on my Honda's.
The video gives a good way to test for it. Mike also explains that for on board, contractors and larger genesis, the problem normally doesn't exist.
Progressive Industries RV Surge and Electrical Protection industry lea
BTW, the plug can be made by just adding a small wire between the ground and neutral pole of a replacement plug.