Onan carb question

boybach

boybach

Well-known member
Dec 9, 2020
1,031
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Looking at the carb float bowl from the left side of my 6000w Onan, at the very bottom of the bowl there's a brass needle valve with a flat on one
side staring you in the face. Not sure what it does, but gas was dripping out of it today.
I counted the number of turns in from where it was set, then took it out to find the rubber(?) seal to be a bit hard and slightly chewed up.

When I tried to remove the seal from the valve, it snapped, so I took some electrical shrink tubing and shrank on and trimmed three layers of the
stuff, ending up with roughly the same profile and shape as the broken piece. Any port in a storm etc.

Fortunately, after I reinstalled the needle valve with the "new" seal, there was no more leaking and the Onan fired right up. Tried it again once or
twice a few hours later and all was still good, with Genset starting immediately each time.

What is that valve's purpose?

Larry
--
Larry - Victoria BC -

1977 Palm Beach 40,000 miles, PO said everything working but forgot the word NOT. New Atwood fridge, water heater & furnace. New SS exhaust system,
6000w Onan, Iota Converter, R134A A/C, New fuel lines & heat exchange hoses
 
That is the main metering fuel valve.

> Looking at the carb float bowl from the left side of my 6000w Onan, at the
> very bottom of the bowl there's a brass needle valve with a flat on one
> side staring you in the face. Not sure what it does, but gas was dripping
> out of it today.
> I counted the number of turns in from where it was set, then took it out
> to find the rubber(?) seal to be a bit hard and slightly chewed up.
>
> When I tried to remove the seal from the valve, it snapped, so I took some
> electrical shrink tubing and shrank on and trimmed three layers of the
> stuff, ending up with roughly the same profile and shape as the broken
> piece. Any port in a storm etc.
>
> Fortunately, after I reinstalled the needle valve with the "new" seal,
> there was no more leaking and the Onan fired right up. Tried it again once
> or
> twice a few hours later and all was still good, with Genset starting
> immediately each time.
>
> What is that valve's purpose?
>
> Larry
> --
> Larry - Victoria BC -
>
> 1977 Palm Beach 40,000 miles, PO said everything working but forgot the
> word NOT. New Atwood fridge, water heater & furnace. New SS exhaust system,
> 6000w Onan, Iota Converter, R134A A/C, New fuel lines & heat exchange hoses
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>

--
Jim Kanomata ASE
Applied/GMC, Newark,CA
jimk
http://www.gmcrvparts.com
1-800-752-7502
 
Thanks Jim, so if she runs good at my setting all is ok then?

Larry
--
Larry - Victoria BC -

1977 Palm Beach 40,000 miles, PO said everything working but forgot the word NOT. New Atwood fridge, water heater & furnace. New SS exhaust system,
6000w Onan, Iota Converter, R134A A/C, New fuel lines & heat exchange hoses
 
You could have used a 1/4” od x 1/8” id O ring. It works very well as a replacement.

Emery Stora
77 Kingsley
Frederick CO

>
> Thanks Jim, so if she runs good at my setting all is ok then?
>
> Larry
> --
> Larry - Victoria BC -
>
> 1977 Palm Beach 40,000 miles, PO said everything working but forgot the word NOT. New Atwood fridge, water heater & furnace. New SS exhaust system,
> 6000w Onan, Iota Converter, R134A A/C, New fuel lines & heat exchange hoses
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
 
> You could have used a 1/4” od x 1/8” id O ring. It works very well as a replacement.
>
> Emery Stora
> 77 Kingsley
> Frederick CO

Thanks, will pick up some for spares, none at hand yesterday so I did what I could to effect a repair - (and was lucky my plan worked :))

Will test setting as per the manual today, I see that the correct position of that valve is set at heavy load - I set it with no load yesterday, so it
could still be off.

Larry
--
Larry - Victoria BC -

1977 Palm Beach 40,000 miles, PO said everything working but forgot the word NOT. New Atwood fridge, water heater & furnace. New SS exhaust system,
6000w Onan, Iota Converter, R134A A/C, New fuel lines & heat exchange hoses
 
Turn in till it bottoms out gently , then back ot about 3- 3 1/2 turn and
fire it up and load the gen with A/C or microwave , then set it in that
range.

> > You could have used a 1/4” od x 1/8” id O ring. It works very well as a
> replacement.
> >
> > Emery Stora
> > 77 Kingsley
> > Frederick CO
>
> Thanks, will pick up some for spares, none at hand yesterday so I did what
> I could to effect a repair - (and was lucky my plan worked :))
>
> Will test setting as per the manual today, I see that the correct position
> of that valve is set at heavy load - I set it with no load yesterday, so it
> could still be off.
>
> Larry
> --
> Larry - Victoria BC -
>
> 1977 Palm Beach 40,000 miles, PO said everything working but forgot the
> word NOT. New Atwood fridge, water heater & furnace. New SS exhaust system,
> 6000w Onan, Iota Converter, R134A A/C, New fuel lines & heat exchange hoses
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>

--
Jim Kanomata ASE
Applied/GMC, Newark,CA
jimk
http://www.gmcrvparts.com
1-800-752-7502
 
> Turn in till it bottoms out gently , then back ot about 3- 3 1/2 turn and
> fire it up and load the gen with A/C or microwave , then set it in that
> range.
>
> --
> Jim Kanomata ASE
> Applied/GMC, Newark,CA
> jimk
> http://www.gmcrvparts.com
> 1-800-752-7502

Thanks Jim, I had it running with the valve set where it was before I took it out - then I switched on the A/C and the Onan didn't miss a beat. It
kept running smoothly and revs stayed constant so I didn't mess with it.

Larry
--
Larry - Victoria BC -

1977 Palm Beach 40,000 miles, PO said everything working but forgot the word NOT. New Atwood fridge, water heater & furnace. New SS exhaust system,
6000w Onan, Iota Converter, R134A A/C, New fuel lines & heat exchange hoses
 
> > Turn in till it bottoms out gently , then back ot about 3- 3 1/2 turn and
> > fire it up and load the gen with A/C or microwave , then set it in that
> > range.
> >
> > --
> > Jim Kanomata ASE
> > Applied/GMC, Newark,CA
> > jimk
> > http://www.gmcrvparts.com
> > 1-800-752-7502
>
> Thanks Jim, I had it running with the valve set where it was before I took it out - then I switched on the A/C and the Onan didn't miss a beat. It
> kept running smoothly and revs stayed constant so I didn't mess with it.
>
> Larry

Just in case you didn't know, there is a 2 minute delay on the rooftop A/C unit before the compressor comes on, so it might have been just the fan
load if you didn't wait. (I just found this out a few days ago)

--
Burl Vibert
Kingston, Ontario
1976 GMC 26 foot, Sheridan reno, don't know original model but we call her Roxie
 
> Just in case you didn't know, there is a 2 minute delay on the rooftop A/C unit before the compressor comes on, so it might have been just the fan
> load if you didn't wait. (I just found this out a few days ago)

Actually I did know that, at least that's how my home A/C works ...good chance I didn't wait long enough though, IIRC it did feel cold but it was a
cool morning so I'll do it again tomorrow! Thanks for picking up on that!

Larry
--
Larry - Victoria BC -

1977 Palm Beach 40,000 miles, PO said everything working but forgot the word NOT. New Atwood fridge, water heater & furnace. New SS exhaust system,
6000w Onan, Iota Converter, R134A A/C, New fuel lines & heat exchange hoses
 
That's the main power adjustment needle. Whatever you use there should be resistant to gasoline. I doubt the heat shrink is so. I recently rebuilt by
Onan carb using a kit that I purchased based on the stampings on the carb body. The kit came with a new o-ring.

> Looking at the carb float bowl from the left side of my 6000w Onan, at the very bottom of the bowl there's a brass needle valve with a flat on one
> side staring you in the face. Not sure what it does, but gas was dripping out of it today.
> I counted the number of turns in from where it was set, then took it out to find the rubber(?) seal to be a bit hard and slightly chewed up.
>
> When I tried to remove the seal from the valve, it snapped, so I took some electrical shrink tubing and shrank on and trimmed three layers of the
> stuff, ending up with roughly the same profile and shape as the broken piece. Any port in a storm etc.
>
> Fortunately, after I reinstalled the needle valve with the "new" seal, there was no more leaking and the Onan fired right up. Tried it again once
> or twice a few hours later and all was still good, with Genset starting immediately each time.
>
> What is that valve's purpose?
>
> Larry

--
Corey P /

Hilliard, OH /
1974 Glacier 26' /
3.70 FD /
ION Wheels
 
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