Onan Marquis 7000 gas generator problem

[Frank W.]

Our generator was replaced by the PO and currently has about 320 hours. It is a Onan Marquis 7000 gasoline generator. Until last weekend, just normal servicing done - never any problems.

We ran the unit with no problems, shut down, and next morning it would not stay running. The start switch when depressed turns over the unit, it starts and runs normally (no funny noises or smoke), but as soon as you release the start button back to the neutral position the unit stops.

I've checked the main wiring, oil level and fuel supply and such...what is odd is that it starts right up, runs fine, until you release the switch, then it dies. This unit has an error code flasher that will code any common problems - and at this point no codes have been generated.

I am trying to sort this out, my initial thoughts are that one of the three start/stop switches has failed. I'm going digging in further soon, but wanted to see if anyone had any advice.

Thanks!

[Joatha]

I had the same problem on my Onan recently. My problem turned out to be a burned out voltage regulator that occurred due to improper voltage from the brushes (determined via the means mentioned in my link below). A light sanding on the brushes and the slip rings and it was putting out the correct voltage. Then, the voltage regulator had to be replaced and I was good to go.

There are 2 reasons they don't stay running. First is low oil. You checked that. But, you might want to also check the low oil switch and make sure its working. Second reason is that the control board isn't getting voltage. On the second, you either have a problem with the voltage output, the voltage regulator, or the control board.

Here's a good guide to help you out. The voltage regulator from this company is what is now on my Onan in my SOB. I don't know what your model number is for a Marquis nor the year of your Marquis. But, this might be of some help.

http://www.flightsystems.com/pdf/onanrvtshootgd608.pdf

[Frank W.]

Joatha, thanks for that link for Flight Systems....exactly what I needed.