Onan 2800 Altitude Adjustment problem

[ManWonder]

I've been working on a surging at idle problem with my Onan 2800. It is located underneath my 2004 190P and it is a giant PITA to work on due to lack of access. Anyways, I noticed something peculiar as I was spraying carb cleaner in it; the little plastic indicator that I have seen in pictures and videos for altitude adjustment is missing. So I have no idea if it is set correctly. I played with it a bit being careful to return the setting to were it was but was wondering if anyone can tell me how, without the indicator, I could know if it is set correctly.

[booster]

A lot of them have limiter on them for emissions rules, and when they come back from Onan for work, the plastic know is always gone because they take it and it's limiter off to get more range. The altitude adjustment is really just a mixture adjustment, so it can be very useful if you are working on cleaning out with Seafoam, as you can adjust the mixture to run better as it cleans out.

If you look at your manual, or one on line, it will show which way to turn the adjuster for higher of lower altitude. You would want to turn it in the lower altitude direction to compensate for plugging and surging. We had it to the full low altitude, richest setting, beyond the limiter, when we were cleaning ours out, as it was the only place it would run very well.

[BBQ]

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Not sure which model is this

[ManWonder]

Originally Posted by BBQ

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Not sure which model is this

That looks like mine minus the little black dial with the pointer on it. I guess I'll have to delve into the manual and fiddle with it some more...

[booster]

Originally Posted by ManWonder

That looks like mine minus the little black dial with the pointer on it. I guess I'll have to delve into the manual and fiddle with it some more...

It probably is, and the turn direction is almost always the same on them. I would turn it nearly as far to the zero altitude to see if it runs better. The shaft should turn pretty easily, and may even have a slot in it that a screwdriver will fit. It is perfectly OK to adjust it while the generator is running, just make slow changes to give a chance to settle on the new setting.

[ManWonder]

Originally Posted by booster

I would turn it nearly as far to the zero altitude to see if it runs better...

so there's the rub... i cannot determine if it's at zero or anything else because i am missing the indicator

[booster]

You can see which way to turn the shaft from BBQ's pic, counterclockwise.

If it runs now, just start it and then slowly turn it CCW to get the best running. Going to far shouldn't hurt anything, but if it starts run rich, you back off a little. If you are currently surging, you are likely very lean and plugged, so it is probable that the adjustment won't get you too rich, but could easily make it run better. As you get the gum out of it, it will start to run richer and you start moving the shaft back clockwise in steps until it all stops changing with more time and cleaning. That would be the right setting for the altitude you are at, and can go from there for real altitude changes, if needed. Then all you need to do is keep it from plugging again.