Most times your looking at some sort of safety device that won't allow the engine to start.Especially after all the work you've done.Check for an electrical connection that would sense oil level,they are the most common and are designed to shut down the engine because of a low oil level.What it does is grounds out the ignition or spark output.I hunted around for something on your gen set but because of it's age there's nothing available.So this is all I can do for you.Last but not least,your local CAT heavy equipment dealer services your gen set.Hope this helps?