If you are new to Diesel engines/Diesel Generators, they function differently than standard gasoline or propane type of engines. The diesel generators typically have glow plugs in each cylinder that "glow hot" in the combustion chamber at cold weather start up. If the glow plugs aren't functioning, the generator will have a hard time starting in cold weather or not start at all. My generator is brand new, so I had doubts that all 3 glow plugs were bad from the get go. Luckily, my issue was a simple blown fuse that sends power to the glow plugs. If your generator is maintained and exercised regularly, they should start on the first try regardless of weather. If you are having problems getting your generator started, there are issues that are causing them.

This video is for Onan Diesel generators only. If you have a gas model, and have hard start conditions, it's typically old gas in the carb, and you are not exercising your generator enough.