250 nt dies when let off starter.

[Sherrellb]

Good afternoon I have a miller 250 nt onan motor. That will not stay running. Usually I'll just choke it let it fire up then take choke off and fire it up and put ignition to run and all is good. But yesterday I went to cranke it and as soon as it fires up I let off the start and it dies. So I tried just holding the start engaged and it runs like a top as it should but when I let it go and it goes to the run position it dies as if I put it into the off position. Any help would be appreciated.
I feel like it is my ignition switch but would like to know how to check it so I don't waist money on it if not what is wrong.
Tgank you in advance for your help

[cruizer]

Oil pressure switch is not sencing oil pressure. Probably just clogged, or needs a new one. Not a big deal though

[Sherrellb]

Oil pressure switch is not sencing oil pressure. Probably just clogged, or needs a new one. Not a big deal though

Thank you for replying. After I posting this I had done lil more research. And I bypassed the oil pressure switch and it ran as normal. I'll be buying a new one and changing the oil. Hopefully that will be it.
Thanks again