Home » Public Forums » GMCnet » Onan carb problems
| Onan carb problems [message #91470] |
Wed, 07 July 2010 20:38  |
GMCNUSA
Messages: 283
Registered: August 2006
Location: Indianapolis, IN
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My Onan generator has never been used very often by us but I have no dash A/C and am tired of driving in the heat. The Onan has been running rough lately. This week I was using it to run roof air and it ran about 30 min and died and then would only run a few minutes at a time. So I decided to check filters in fuel pump and carb bowl, they looked perfect. When I reassembled everything the carb poured fuel out of it. I cleaned float valve and reassembled and still leaked. Bought carb rebuild kit replaced float valve and it still leaks.
Does the fuel pump have a regulator in it? Is it possible for the pump to be passing to much pressure and forcing float valve open? What is the pressure supposed to be? I checked the pressure with a 0 to 30 PSI gauge and it read 5 PSI is this too high? Any thoughts will be welcomed.
Thanks
Larry Dilk
Indianapolis, IN
76 Eleganza II
Patterson 455,Turbo City TBI,
Just LOVE It!
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| Re: Onan carb problems [message #91477 is a reply to message #91470] |
Wed, 07 July 2010 21:54  |
tphipps
Messages: 3005
Registered: August 2004
Location: Spanish Fort, AL
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If it leaks around the edge of the float bowl, there is a very thin "O" shaped flat gasket that goes between the body of the carb and the float bowl. Very fragile and easy to dislodge and tear. M&D mower can get you the gasket kit ($7.50), but it takes about two weeks for it to show up. I have no idea how much Onan gets for the gasket set. Carb rebuild kits are no longer available from Welbros (I think that is the right name.) Maybe JmK has a carb kit available.
Tom Phipps,
75 GMC with leaky carb bowl (on the list next)
2012 Phoenix Cruiser model 2552
KA4CSG
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| Re: Onan carb problems [message #91480 is a reply to message #91470] |
Wed, 07 July 2010 22:05 |
Craig Lechowicz
Messages: 541
Registered: October 2006
Location: Waterford, MI
Karma: 0
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| GMCNUSA wrote on Wed, 07 July 2010 21:38 |
The Onan has been running rough lately. Does the fuel pump have a regulator in it? Is it possible for the pump to be passing to much pressure and forcing float valve open? What is the pressure supposed to be? I checked the pressure with a 0 to 30 PSI gauge and it read 5 PSI is this too high? Any thoughts will be welcomed.
Thanks
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Larry,
I'm not sure how much pressure is too much, but there was a thread on Onan fuel pumps a while back, and they have a 4-5 psi version and a 1-2 psi version. I think the 1-2 psi one is the right one for our application, but not sure if that's the only problem.
Craig Lechowicz
'77 Kingsley, Waterford, MI
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| Re: [GMCnet] Onan carb problems [message #91490 is a reply to message #91470] |
Wed, 07 July 2010 22:36 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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Larry,
I was speaking with Duane Simmons about a similar problem. His thought was
that possibly the plastic connector for the board going to the inside of the
coach could be getting warm enough to loose contact and thus shut down.
We have adjusted the engine valves, replaced coils,etc.
Worth a try to work on it.
On Wed, Jul 7, 2010 at 6:38 PM, Larry and Cheryl Dilk <lwd222@msn.com>wrote:
>
>
> My Onan generator has never been used very often by us but I have no dash
> A/C and am tired of driving in the heat. The Onan has been running rough
> lately. This week I was using it to run roof air and it ran about 30 min and
> died and then would only run a few minutes at a time. So I decided to check
> filters in fuel pump and carb bowl, they looked perfect. When I reassembled
> everything the carb poured fuel out of it. I cleaned float valve and
> reassembled and still leaked. Bought carb rebuild kit replaced float valve
> and it still leaks.
> Does the fuel pump have a regulator in it? Is it possible for the pump to
> be passing to much pressure and forcing float valve open? What is the
> pressure supposed to be? I checked the pressure with a 0 to 30 PSI gauge and
> it read 5 PSI is this too high? Any thoughts will be welcomed.
> Thanks
>
> --
> Larry Dilk
> Indianapolis, IN
> 76 Eleganza II
> Patterson 455,Turbo City TBI,
> Just LOVE It!
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
--
Jim Kanomata
Applied/GMC, Fremont,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
_______________________________________________
GMCnet mailing list
List Information and Subscription Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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| Re: [GMCnet] Onan carb problems [message #91491 is a reply to message #91477] |
Wed, 07 July 2010 22:39 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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We keep around 12-20 carb kits in stock along with rebuild units .
On Wed, Jul 7, 2010 at 7:54 PM, Thomas Phipps <tph1pp5@yahoo.com> wrote:
>
>
> If it leaks around the edge of the float bowl, there is a very thin "O"
> shaped flat gasket that goes between the body of the carb and the float
> bowl. Very fragile and easy to dislodge and tear. M&D mower can get you
> the gasket kit ($7.50), but it takes about two weeks for it to show up. I
> have no idea how much Onan gets for the gasket set. Carb rebuild kits are
> no longer available from Welbros (I think that is the right name.) Maybe
> JmK has a carb kit available.
>
> Tom Phipps,
> 75 GMC with leaky carb bowl (on the list next)
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
--
Jim Kanomata
Applied/GMC, Fremont,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
_______________________________________________
GMCnet mailing list
List Information and Subscription Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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| Re: [GMCnet] Onan carb problems [message #91493 is a reply to message #91490] |
Wed, 07 July 2010 23:18 |
GMCNUSA
Messages: 283
Registered: August 2006
Location: Indianapolis, IN
Karma: 0
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[quote title=jimk wrote on Wed, 07 July 2010 23:36]Larry,
I was speaking with Duane Simmons about a similar problem. His thought was
that possibly the plastic connector for the board going to the inside of the
coach could be getting warm enough to loose contact and thus shut down.
We have adjusted the engine valves, replaced coils,etc.
Worth a try to work on it.
> > >
--
Jim Kanomata
Applied/GMC, Fremont,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
Jim that board poblem may be my shutting down cause. But right now I need to figure out the carb over flowing. All gaskets are in place and I put in a rebuild kit and it still overflows. Thanks
Larry Dilk
Indianapolis, IN
76 Eleganza II
Patterson 455,Turbo City TBI,
Just LOVE It!
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| Re: [GMCnet] Onan carb problems [message #91496 is a reply to message #91493] |
Wed, 07 July 2010 23:35 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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[quote title=GMCNUSA wrote on Wed, 07 July 2010 23:18]| jimk wrote on Wed, 07 July 2010 23:36 |
Larry,
I was speaking with Duane Simmons about a similar problem. His thought was
that possibly the plastic connector for the board going to the inside of the
coach could be getting warm enough to loose contact and thus shut down.
We have adjusted the engine valves, replaced coils,etc.
Worth a try to work on it.
> > >
--
Jim Kanomata
Applied/GMC, Fremont,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
Jim that board problem may be my shutting down cause. But right now I need to figure out the carb over flowing. All gaskets are in place and I put in a rebuild kit and it still overflows. Thanks
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Larry,
Do not get mad at me.
Is the needle still in it's hole?
I have dropped a few when reassembling those small carbs.
I cannot remember if that is the type that has the little very thin wire keeper on the needle valve.
Ken B.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Onan carb problems [message #91499 is a reply to message #91496] |
Wed, 07 July 2010 23:44 |
GMCNUSA
Messages: 283
Registered: August 2006
Location: Indianapolis, IN
Karma: 0
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Senior Member |
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[
Larry,
Do not get mad at me.
Is the needle still in it's hole?
I have dropped a few when reassembling those small carbs.
I cannot remember if that is the type that has the little very thin wire keeper on the needle valve.
Ken B. [/quote]
Hi Ken; Yes I checked that, in fact I took carb off and dissassembled it so many times I'm sure it is in there and I set the float level as the GMC manual says at 3/16 in and then adjusted it a little open and it still leaks. This leaking started after I removed and replaced the filter in the bottom of fuel pump. Thanks for the idea.
Larry Dilk
Indianapolis, IN
76 Eleganza II
Patterson 455,Turbo City TBI,
Just LOVE It!
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| Re: [GMCnet] Onan carb problems [message #91500 is a reply to message #91499] |
Wed, 07 July 2010 23:50 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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| GMCNUSA wrote on Wed, 07 July 2010 23:44 |
[
Larry,
Do not get mad at me.
Is the needle still in it's hole?
I have dropped a few when reassembling those small carbs.
I cannot remember if that is the type that has the little very thin wire keeper on the needle valve.
Ken B.
|
Hi Ken; Yes I checked that, in fact I took carb off and dissassembled it so many times I'm sure it is in there and I set the float level as the GMC manual says at 3/16 in and then adjusted it a little open and it still leaks. This leaking started after I removed and replaced the filter in the bottom of fuel pump. Thanks for the idea.[/quote]
Maybe try this
Take the float bowl off. Hold the float up with your finger. Power the fuel pump and see if it still leaks while you are holding the the needle valve against the seat.
If it seals (doesn't leak) then we have a problem with the seals around the bottom and sides of the float bowl.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Onan carb problems [message #91501 is a reply to message #91500] |
Wed, 07 July 2010 23:53 |
GMCNUSA
Messages: 283
Registered: August 2006
Location: Indianapolis, IN
Karma: 0
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Senior Member |
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| Ken Burton wrote on Thu, 08 July 2010 00:50 |
| GMCNUSA wrote on Wed, 07 July 2010 23:44 |
[
Larry,
Do not get mad at me.
Is the needle still in it's hole?
I have dropped a few when reassembling those small carbs.
I cannot remember if that is the type that has the little very thin wire keeper on the needle valve.
Ken B.
|
Hi Ken; Yes I checked that, in fact I took carb off and dissassembled it so many times I'm sure it is in there and I set the float level as the GMC manual says at 3/16 in and then adjusted it a little open and it still leaks. This leaking started after I removed and replaced the filter in the bottom of fuel pump. Thanks for the idea.
|
Maybe try this
Take the float bowl off. Hold the float up with your finger. Power the fuel pump and see if it still leaks while you are holding the the needle valve against the seat.
If it seals (doesn't leak) then we have a problem with the seals around the bottom and sides of the float bowl.
[/quote]
GREAT idea I will try that in the morning.
Larry Dilk
Indianapolis, IN
76 Eleganza II
Patterson 455,Turbo City TBI,
Just LOVE It!
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