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Onan carb question [message #365139]

Wed, 30 June 2021 22:25

boybach

Messages: 566
Registered: December 2020
Location: Vancouver Island

Karma: 4

Senior Member

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 ex-Palm Beach "Ol' Leaky" 40,000 miles, PO said everything working but forgot the word NOT. Atwood helium fridge, water heater & furnace. SS exhaust system, Onan, Iota Converter, R134A, New fuel lines & heat exchange hoses

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[GMCnet] Re: Onan carb question [message #365142 is a reply to message #365139]

Wed, 30 June 2021 23:13

jimk

Messages: 6734
Registered: July 2006
Location: Belmont, CA

Karma: 9

Senior Member

That is the main metering fuel valve.

On Wed, Jun 30, 2021 at 8:26 PM wrote:

> 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@appliedairfilters.com
http://www.gmcrvparts.com
1-800-752-7502
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Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502

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Re: [GMCnet] Re: Onan carb question [message #365143 is a reply to message #365142]

Wed, 30 June 2021 23:31

boybach

Messages: 566
Registered: December 2020
Location: Vancouver Island

Karma: 4

Senior Member

Thanks Jim, so if she runs good at my setting all is ok then?

Larry

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[GMCnet] Re: Onan carb question [message #365146 is a reply to message #365143]

Thu, 01 July 2021 07:27

stu@97381.com, Emery

Messages: 232
Registered: June 2020

Karma: 2

Senior Member

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

> On Jun 30, 2021, at 10:32 PM, twlldeen@gmail.com wrote:
>
> 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:
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:

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Re: [GMCnet] Re: Onan carb question [message #365150 is a reply to message #365146]

Thu, 01 July 2021 09:46

boybach

Messages: 566
Registered: December 2020
Location: Vancouver Island

Karma: 4

Senior Member

stu@97381.com, Emery wrote on Thu, 01 July 2021 05:27

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 Smile

)

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

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[GMCnet] Re: Onan carb question [message #365158 is a reply to message #365150]

Thu, 01 July 2021 18:35

jimk

Messages: 6734
Registered: July 2006
Location: Belmont, CA

Karma: 9

Senior Member

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.

On Thu, Jul 1, 2021 at 7:47 AM wrote:

> stu@97381.com, Emery wrote on Thu, 01 July 2021 05:27
>> 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@appliedairfilters.com
http://www.gmcrvparts.com
1-800-752-7502
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:

Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502

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Re: [GMCnet] Re: Onan carb question [message #365160 is a reply to message #365158]

Thu, 01 July 2021 22:27

boybach

Messages: 566
Registered: December 2020
Location: Vancouver Island

Karma: 4

Senior Member

jimk wrote on Thu, 01 July 2021 16:35

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@appliedairfilters.com
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

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Re: [GMCnet] Re: Onan carb question [message #365161 is a reply to message #365160]

Thu, 01 July 2021 22:52

blur911

Messages: 166
Registered: December 2020
Location: Kingston, Ontario

Karma: 4

Senior Member

boybach wrote on Thu, 01 July 2021 22:27

jimk wrote on Thu, 01 July 2021 16:35
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@appliedairfilters.com
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

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Re: [GMCnet] Re: Onan carb question [message #365162 is a reply to message #365161]

Fri, 02 July 2021 01:31

boybach

Messages: 566
Registered: December 2020
Location: Vancouver Island

Karma: 4

Senior Member

blur911 wrote on Thu, 01 July 2021 20:52

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

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Re: Onan carb question [message #365165 is a reply to message #365139]

Fri, 02 July 2021 06:32

uprooted

Messages: 72
Registered: December 2019
Location: Hilliard, OH

Karma: 0

Member

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.

boybach wrote on Wed, 30 June 2021 23:25

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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