Onan 4k Altitude Adjustment Screw Setting.

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StutterHead

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Mar 27, 2016
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Hello all, I'm hopeful all someone can point me in the right direction on were to start with my issue.  I have an Onan 4k EVAP gene (2010) somehow the plastic limiter cap is missing from the alitutude adjuster screw and no i really have no idea where the current setting is now.  And of course the gene is having difficultly running for more than an hour or so with a load before shutting down.  Does anybody have any knowledge as to how many turns out the screw should be to essentially be at 0ft/Sealevel?
thanks for the help!
 
No Idea! But running for an hour and shutting down is probably an overheating problem. Try blowing out the dust and crud collected in the compartment.  It worked for me. :)

Ernie
 
I have no clue either, but if it runs ok for an hour, the altitude adjustment is probably NOT the problem.

Your Onan EVAP has self-diagnostics, so a code will be available to say why it shut down. Often the code is very specific, so get that code to see what is wrong. Your Onan manual will tell you how to read the code (usually a blinking light).
 
Great points Guys..  I'll definitely look into overheating as the issue and clean any gunk out. Is there any sensors to check or replace?
 
If your altitude adjustment is set for high altitude and you are at sea level your genny is running lean. If it's running lean it could be running hot. If it's air-cooled they need to run a wee bit rich to aid in cooling. The vaporization of the slightly rich mixture helps dissipate heat from the heads and valves. See if you have good airflow and maybe back the screw out a 1/4 turn see what happens, lefty loosey. Make a mark with an awl or something so screw can be returned to the original position if needed.

Bill
 
Thanks everybody for all the input. I tinkered with it again yesterday. I confirmed there is no nests or gunk stopping airflow.  I ran the A/C and again, it ran for an hour and stopped.  I unscrewed the bowl screw and it was DRY- no fuel came out of the bowl.  But, fuel did resume once I primed it.  Then it started right back up and ran for another 30 min...  I'm ready for more input!!!
 
Ditto fuel pump, but also check the fuel lines and fittings. Assuming you have sufficient fuel in the tank well above the pick-up line, sometimes the fuel fittings can need tightening (happen to me) or the lines themselves are cracked or aged to the point that they allow air to be sucked in (also happened to me) to the point that the fuel pump can't supply sufficient fuel.
 
UPDATE and it's SOLVED!!!  all those who voted fuel pump where correct.  Ended up taking it to dealer.  Changed fuel pump and filter and set altitude screw for 0' sea level ( it wasn't off much). Just returned from a desert trip with my son and put over 12 hours on the gene with no issues to speak of. 
Again, thanks to all for adding opinions...

 
 
Hello all, I'm hopeful all someone can point me in the right direction on were to start with my issue. I have an Onan 4k EVAP gene (2010) somehow the plastic limiter cap is missing from the alitutude adjuster screw and no i really have no idea where the current setting is now. And of course the gene is having difficultly running for more than an hour or so with a load before shutting down. Does anybody have any knowledge as to how many turns out the screw should be to essentially be at 0ft/Sealevel?
thanks for the help!

Edit: I just realized I again replied to a very old message! But I will leave this one stand for the info in it:

Screw it all the way in (most lean)and back out a half turn to be in the mid range. A full turn out will be more rich.

At least that is how my Chinese replacement carb for my Onan works. I assume Onan will be the same. The elevation adjustment is really a gas get. Less gas enters all the way in CW. CCW lets more gas in.

Best to start out with a new spark plug and the screw nearly all the way in. Once you get too much crud on the spark plug, you will have problems trying to adjust it.

FWIW, I recently over-tightened that jet-screw on mine when I was recently above 7K' elevation. It broke, so now I cannot adjust it. But It still runs perfectly here at 1,400' elevation set for as lean as possible, so I will just keep mine as is. It seems to me that 4K Onans run a bit on the rich side when adjusted for the exact elevation (by the label) anyway, regardless if the Onan or the Chinese carb.

-Don- Auburn, CA
 
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