Onan 5.5HGJAB Spec K - High Altitude

[6.7LMegaCab]

The generator currently runs pretty well - but it is about due for the 450-hour service (valve lash adjustment). I found the latest operators and service manual that covers this generator through the Cummins QuickServe. Through some reading I discovered that when running the GenSet above 5K feet, it will need a high altitude kit. My goodness, those carbs are expensive! Not much of a kit, rather than a whole carb replacement.

We live just a smidge below 6K feet and mostly camp between 6500 and 8K feet - more typically between 6-7K. How necessary is the high altitude carb? Is there a "poor man's" fix that can be done to garner the right air-fuel mixture above 5K feet? Is there a high-altitude jet kit that would be a better alternative?

Thanks!

 

[taskswap]

Well, it's Cummins, you wouldn't want those poor engineers to starve, would you??

Given who it is, I'm not super surprised they want a whole new carb. You didn't post your model number but with some searching I bet you can find a jet kit for it and probably a Youtube video or two.

Do you need to? Almost certainly not, if it's been working well so far for you. Running too lean is very bad, but running too rich usually just leads to a bit of power loss and quicker fouling. Not my place to give advice but if it was me I'd check the plug and if it was OK, I wouldn't mess with it.

 

[danemayer]

Our Onan 5500 is the propane model, so perhaps it's not as sensitive. It has run just fine at 9200 ft.

However, I also have a dual fuel 10,000 watt Firmin generator at home. I installed the high-altitude kit (free) because they said the output wattage would be somewhat reduced at 7400 ft without it.

 

[6.7LMegaCab]

Well, it's Cummins, you wouldn't want those poor engineers to starve, would you??

Given who it is, I'm not super surprised they want a whole new carb. You didn't post your model number but with some searching I bet you can find a jet kit for it and probably a Youtube video or two.

Do you need to? Almost certainly not, if it's been working well so far for you. Running too lean is very bad, but running too rich usually just leads to a bit of power loss and quicker fouling. Not my place to give advice but if it was me I'd check the plug and if it was OK, I wouldn't mess with it.

Well, now that you mentioned it, yes, yes I would...a steak on their table or a steak on mine? Have you checked meat prices recently? I'm about ready to start raising my own beef The model number is in the subject.

Fair enough - I'll be heading to El Paso on Thursday and figured I'd see if the Cummins dealer has the valve cover gasket in stock and while I'm at it just put in a new set of plugs after adjusting the valves....if they need to be changed - haven't pulled them yet. Otherwise, it'll be nice to have a set on hand anyhow.

 

[6.7LMegaCab]

Our Onan 5500 is the propane model, so perhaps it's not as sensitive. It has run just fine at 9200 ft.

However, I also have a dual fuel 10,000 watt Firmin generator at home. I installed the high-altitude kit (free) because they said the output wattage would be somewhat reduced at 7400 ft without it.

I wish we had the propane model - I was looking at the specs today between propane and even the 7K and the engines are the same...almost got me thinking on a rebuild but quickly abandoned that thought.

Anyhow - it kind of sputters sometimes, but never really had a problem with it - other than when a magneto went out a few years ago.

I bought a 9200 Watt Predator last year that I installed the high altitude kit on when I first got it. I suppose if I really need to worry about higher altitudes and the Onan - I'll just bring that behemoth along for the ride.

Now that I think of it - we did spend a few days in Colorado last year at about 8K feet and the generator did run fine...so perhaps all that reading got me thinking I needed to upgrade for no reason. I'll just keep an eye on it for now!

Thank you!