Peg, We have some outstanding genset techs here, especially for the ONAN brand. For them to help you best, they must have the full Model Number and Spec Code. The Spec is actually the last character of the Model. The very popular "4KY" has had Spec changes to "K" and probably beyond. KY has no oil pump, oil filter or oil pressure switch. That's because it is Splash Lubricated like a small mower engine. It HAD an Oil Level Switch but that was deleted before the Spec got to K, which is what ours is.
Knowing what you have will help us help you. No need to troubleshoot a feature that you don't even have!