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tony_lee's avatar
tony_lee
Explorer
Jun 19, 2015

Onan propane generator operation at high altitude

Don't use it very often as propane supply here is quite problematic, but just wondered what the altitude limits were on an Onan Microlight 2500LP

We are at Cusco, Peru at 11,200 feet (and we have camped quite a bit higher at times). Unit cranks easily and fast but no sign of ignition - and all other appliances work normally on the propane. Doesn't mean there isn't something about the propane quality, but given the problems some vehicles have starting at this altitude, I assume the problem might be more to do with altitude and fuel air mixture.
Last time I used it was at a much lower altitude and it ran the aircon all night with no problems. Well, not entirely without problems as finding supplies of propane in Brazil where bottle designs are entirely different required some innovative solutions.

Anyone have any insights please.

9 Replies

  • Good troubleshooting! Be aware that you loose about 3% of power for every 1000 feet of elevation increase so your 2500 generator is only about a 1600 generator now.
  • All's well that ends well.

    Thought I'd have another try to get the generator running. Still at the same altitude.
    Held the throttle partly closed instead of fully open as the governor linkage wanted, and it fired straight up. Got such a surprise that I let the governor linkage go and it went to full throttle again as it hadn't reached full speed and the engine died again.
    Tried again but held the linkage for a bit longer until it reached something close to normal speed and it ran as normal.
    Loaded it with the microwave and ran perfectly.

    Guess trying to start it with wide open throttle effectively "flooded" it and the fuel air mixture was so rich it couldn't fire.

    So they will run at 11,000+ feet, just that they need a bit of help getting started.
  • OK, I'll have a more thorough poke around the unit. Would be nice if it did have that feature AND didn't need stripping the generator to find it. I'll do a search on line. Basic instruction book doesn't mention it so I'd say the chances are good that it doesn't exist on my unit

    thanks.

    Quite nice that all the other appliances seem to be remarkably tolerant to altitude. The fridge does sometimes take a couple of tries to light up - and previous owners said it does get flakier still at higher altitudes - but the cooktop, HWS and furnace aren't significantly different.
  • Does your LP Onan have an altitude adjustment knob built-in like our gas Onan does?

    If so, I'm not sure the Onan's adjustment range goes to 11.2K feet ... but at least make sure you have it turned up to the limit of it's high altitude range.
  • "As with any other gas appliance it is starving for air."

    Not the only thing starving for air. Last time we drove here gradually rising in altitude over several weeks but this time it was 1 hour from sea level to high altitude. Gasp.

    Yes, figured it was just a mixture problem so will see how it goes once we get down a bit and then start worrying if it still doesn't start.



    Not sure what sort of carburation it has - but given the LP on the model number, I assume it was done at factory.
  • As with any other gas appliance it is starving for air......way to fuel rich.

    Other than coming down in elevation not much one can do unless you have smaller carb jets with you and can change them out

    Onan does have 'high altitude jet' for some models.
    You would need to look up model specific manual/parts for optional jet

    Norcold/Dometic/Atwood/Suburban have disclaimer about proper functioning above 5500' (Although many of their propane systems function quite very up to 7000' or higher)

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