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| [GMCnet] Onan carb swap [message #232525] |
Sat, 07 December 2013 00:01  |
gcbgold
Messages: 60
Registered: August 2012
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Has anyone tried swapping a carb from a 6k Onan and installing it on a 4k. I just need a way to test a 4k Onan to see if it has a carb problem or not and did not know if it would run properly with 6k carb.
Gary Bovee
1978 Royale
Red Bluff, CA
Free "Internet Idiot's Guide for GMC MotorHome Information" - www.gmcidiotsguide.com
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| Re: [GMCnet] Onan carb swap [message #232535 is a reply to message #232525] |
Sat, 07 December 2013 05:32  |
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mike miller
Messages: 3576
Registered: February 2004
Location: Hillsboro, Oregon
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Gary,
If all you want to do is BORROW a 4k Onan carb, Just walk around behind your shop and borrow mine.... just put it back when you are done.
I am parking there rent free!
Mike Miller -- Hillsboro, OR -- on the Black list
(#2)`78 23' Birchaven Rear Bath -- (#3)`77 23' Birchaven Side Bath
More Sidekicks than GMC's and a late model Malibu called 'Boo'
http://m000035.blogspot.com
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| Re: [GMCnet] Onan carb swap [message #232552 is a reply to message #232525] |
Sat, 07 December 2013 10:45 |
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mike miller
Messages: 3576
Registered: February 2004
Location: Hillsboro, Oregon
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| gcbgold wrote on Fri, 06 December 2013 22:01 |
Has anyone tried swapping a carb from a 6k Onan and installing it on a 4k. I just need a way to test a 4k Onan to see if it has a carb problem or not and did not know if it would run properly with 6k carb.
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IIRC: the carbs are different in shape. Doesn't the 4k carb have a 90 degree bend in it? (I could walk out in my back yard and check, as I have one of each... but it is too cold!)
That said, for troubleshooting all that needs to connect is the manifold end and the fuel line.
What makes you think the carb is bad? Does it "run" on starting fluid?
Mike Miller -- Hillsboro, OR -- on the Black list
(#2)`78 23' Birchaven Rear Bath -- (#3)`77 23' Birchaven Side Bath
More Sidekicks than GMC's and a late model Malibu called 'Boo'
http://m000035.blogspot.com
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| Re: [GMCnet] Onan carb swap [message #232558 is a reply to message #232552] |
Sat, 07 December 2013 12:13 |
gcbgold
Messages: 60
Registered: August 2012
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It idles fine, but won't rev up. You can move the throttle arm and it still just idles.
Gary Bovee
Red Bluff, CA
1978 GMC Royale
Free "Idiot's Internet Guide for Finding GMC MotorHome Information"
www.gmcidiotsguide.com
> On Dec 7, 2013, at 8:45 AM, Mike Miller <m000035@gmail.com> wrote:
>
>
>
> gcbgold wrote on Fri, 06 December 2013 22:01
>> Has anyone tried swapping a carb from a 6k Onan and installing it on a 4k. I just need a way to test a 4k Onan to see if it has a carb problem or not and did not know if it would run properly with 6k carb.
>
>
> IIRC: the carbs are different in shape. Doesn't the 4k carb have a 90 degree bend in it? (I could walk out in my back yard and check, as I have one of each... but it is too cold!)
>
> That said, for troubleshooting all that needs to connect is the manifold end and the fuel line.
>
> What makes you think the carb is bad? Does it "run" on starting fluid?
>
> --
> Mike Miller -- Hillsboro, OR -- on the Black list
> (#1)'73 26' exPainted D. -- (#2)`78 23' Birchaven Rear Bath -- (#3)`77 23' Birchaven Side Bath
> http://m000035.blogspot.com
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| Re: [GMCnet] Onan carb swap [message #232606 is a reply to message #232582] |
Sat, 07 December 2013 19:46 |
gcbgold
Messages: 60
Registered: August 2012
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I was miss leading with original my response. It try's to start and only runs for 5 seconds and dies. It won't rev up at at all if you move the throttle. Compression is 75 on one cylinder and 85 on the other. Tested spark at each plug and it looks good. Replaced plugs, no change. Installed new fuel pump. No change. Installed Pertronix electronic ignition, no change. Check timing when using points or electronic ignition and it was spot on. I guess I will change the carb next. Don't really know what to try. It has me stumped.
Gary Bovee
Red Bluff, CA
1978 GMC Royale
Free "Idiot's Internet Guide for Finding GMC MotorHome Information"
www.gmcidiotsguide.com
> On Dec 7, 2013, at 3:17 PM, Matt Colie <matt7323tze@gmail.com> wrote:
>
>
>
> gcbgold wrote on Sat, 07 December 2013 14:56
>> Matt,
>>
>> I checked the throttle plate and it is opening and closing just fine. I hate to try and pull the intake.
>>
>> Do you know what the compression readings should be for a 4k?
>>
>> Gary Bovee
>
> Gary,
>
> I don't actually know and the current OAT here is such that I am not going to go out and find out, but I would expect it to be in the 65psi region.
>
> You say it only idles... You do know that those only run at 1800 RPM - Right?
>
> Matt
> --
> Matt & Mary Colie
> I am often amused by those who attribute a quote to the character or performer and not the actual author.
> '73 Glacier 23 With 4 Rear Brakes that pull as they should
> SE Michigan - Twixt A2 and Detroit
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| Re: [GMCnet] Onan carb swap [message #232611 is a reply to message #232608] |
Sat, 07 December 2013 20:01 |
gcbgold
Messages: 60
Registered: August 2012
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I think it's worth a try. Thanks Rob.
Gary Bovee
Red Bluff, CA
1978 GMC Royale
Free "Idiot's Internet Guide for Finding GMC MotorHome Information"
www.gmcidiotsguide.com
> On Dec 7, 2013, at 5:58 PM, "Robert Mueller" <robmueller@iinet.net.au> wrote:
>
> Gary,
>
> Get a gallon can of carb cleaner and a rebuild kit from JimK; that should resurrect the carb.
>
> Regards,
> Rob M.
> Sydney, Australia
> AUS '75 Avion-The Blue Streak TZE365V100428
> USA '75 Avion-Double Trouble TZE365V100426
>
> -----Original Message-----
> From: Gary B.
>
> I was miss leading with original my response. It try's to start and only runs for 5 seconds and dies. It won't rev up at at all if
> you move the throttle. Compression is 75 on one cylinder and 85 on the other. Tested spark at each plug and it looks good.
> Replaced plugs, no change. Installed new fuel pump. No change. Installed Pertronix electronic ignition, no change. Check timing
> when using points or electronic ignition and it was spot on. I guess I will change the carb next. Don't really know what to try.
> It has me stumped.
>
> Gary
>
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| Re: [GMCnet] Onan carb swap [message #232613 is a reply to message #232606] |
Sat, 07 December 2013 20:25 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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| gcbgold wrote on Sat, 07 December 2013 19:46 |
I was miss leading with original my response. It try's to start and only runs for 5 seconds and dies. It won't rev up at at all if you move the throttle. Compression is 75 on one cylinder and 85 on the other. Tested spark at each plug and it looks good. Replaced plugs, no change. Installed new fuel pump. No change. Installed Pertronix electronic ignition, no change. Check timing when using points or electronic ignition and it was spot on. I guess I will change the carb next. Don't really know what to try. It has me stumped.
Gary Bovee
Red Bluff, CA
1978 GMC Royale
Free "Idiot's Internet Guide for Finding GMC MotorHome Information"
www.gmcidiotsguide.com
|
1. Bad oil pressure switch
2. No oil pressure. Check oil level with it NOT running.
After verifying that you have oil pressure and that the oil pressure switch is good, you can jumper pins 5 to 9 temporarily and see if it will run that way. If it does then, proceed to steps 3 through 5 with the temporary jumper installed.
3. No or low internal alternator output to the control board. Board pins 5 to 8 should read 28 to 30 VAC
4. If number 3 is the problem disconnect the internal battery charger regulator and try again.
5. Bad component on the board in the K2 relay circuit.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
[Updated on: Sat, 07 December 2013 20:26] Report message to a moderator |
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| Re: [GMCnet] Onan carb swap [message #232622 is a reply to message #232613] |
Sat, 07 December 2013 21:50 |
gcbgold
Messages: 60
Registered: August 2012
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Thanks Ken for the suggestions. I will do all those checks tomorrow and let you know what I find out.
Gary Bovee
Red Bluff, CA
1978 GMC Royale
Free "Idiot's Internet Guide for Finding GMC MotorHome Information"
www.gmcidiotsguide.com
> On Dec 7, 2013, at 6:25 PM, Ken Burton <n9cv@comcast.net> wrote:
>
>
>
> gcbgold wrote on Sat, 07 December 2013 19:46
>> I was miss leading with original my response. It try's to start and only runs for 5 seconds and dies. It won't rev up at at all if you move the throttle. Compression is 75 on one cylinder and 85 on the other. Tested spark at each plug and it looks good. Replaced plugs, no change. Installed new fuel pump. No change. Installed Pertronix electronic ignition, no change. Check timing when using points or electronic ignition and it was spot on. I guess I will change the carb next. Don't really know what to try. It has me stumped.
>>
>> Gary Bovee
>> Red Bluff, CA
>> 1978 GMC Royale
>> Free "Idiot's Internet Guide for Finding GMC MotorHome Information"
>> www.gmcidiotsguide.com
>
> 1. Bad oil pressure switch
> 2. No oil pressure. Check oil level with it NOT running.
> 3. No or low internal alternator output to the control board. Board pins 5 to 8 should read 28 to 30 VAC
> 4. If number 3 is the problem disconnect the internal battery charger regulator and try again.
> 5. Bad component on the board in the K2 relay circuit.
>
> After verifying that you have oil pressure and that the oil pressure switch is good, you can jumper pins 5 to 9 temporarily and see if it will run that way. If it does then, proceed to steps 3 through 5 with the temporary jumper installed.
>
>
>
>
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
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| Re: [GMCnet] Onan carb swap [message #232672 is a reply to message #232613] |
Sun, 08 December 2013 21:53 |
gcbgold
Messages: 60
Registered: August 2012
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Ken,
Tried all your suggestion, but unfortunately the Onan was being stubborn and still will only run for about 6 seconds and dies. Ran out of time and will have to work on it sometime later.
Thanks for help.
Gary Bovee
Red Bluff, CA
1978 GMC Royale
Free "Idiot's Internet Guide for Finding GMC MotorHome Information"
www.gmcidiotsguide.com
> On Dec 7, 2013, at 6:25 PM, Ken Burton <n9cv@comcast.net> wrote:
>
>
>
> gcbgold wrote on Sat, 07 December 2013 19:46
>> I was miss leading with original my response. It try's to start and only runs for 5 seconds and dies. It won't rev up at at all if you move the throttle. Compression is 75 on one cylinder and 85 on the other. Tested spark at each plug and it looks good. Replaced plugs, no change. Installed new fuel pump. No change. Installed Pertronix electronic ignition, no change. Check timing when using points or electronic ignition and it was spot on. I guess I will change the carb next. Don't really know what to try. It has me stumped.
>>
>> Gary Bovee
>> Red Bluff, CA
>> 1978 GMC Royale
>> Free "Idiot's Internet Guide for Finding GMC MotorHome Information"
>> www.gmcidiotsguide.com
>
> 1. Bad oil pressure switch
> 2. No oil pressure. Check oil level with it NOT running.
> 3. No or low internal alternator output to the control board. Board pins 5 to 8 should read 28 to 30 VAC
> 4. If number 3 is the problem disconnect the internal battery charger regulator and try again.
> 5. Bad component on the board in the K2 relay circuit.
>
> After verifying that you have oil pressure and that the oil pressure switch is good, you can jumper pins 5 to 9 temporarily and see if it will run that way. If it does then, proceed to steps 3 through 5 with the temporary jumper installed.
>
>
>
>
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
> _______________________________________________
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| Re: [GMCnet] Onan carb swap [message #232675 is a reply to message #232672] |
Sun, 08 December 2013 22:17 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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If jumpering 5 to 9 did not make it stay running run then you have a fuel pump or fuel delivery problem.
With 5 jumped to 9 do you hear the fuel pump running before cranking the Onan?
If the pump is running does the clicking start out fast and slow down and almost stop after 5 or 10 seconds? If it does then the pump and gas feed to it are OK.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Onan carb swap [message #232680 is a reply to message #232677] |
Mon, 09 December 2013 05:45 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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Based on those symptoms, I suspect that the needle and seat in the carb is sticking or more likely it is clogged / restricted. This is not allowing full fuel flow to the carb float bowl.
I would pull the carb, turn it over and remove the bowl. Be careful to observe how the float, pivot pin and needle valve are assembled. Remove the pivot pin, float, and needle valve.
Clean the tip of the needle valve with carb cleaner and use some spray carb cleaner to clean the seat. Blow carb cleaner back through the seat an out through the gasoline input connection where the gasoline hose is attached. Reassemble the needle seat and float, reinstall the float bowl to the carb and reinstall the carb.
See if it will run now.
| gcbgold wrote on Mon, 09 December 2013 00:07 |
The fuel pump would come on as soon as I connected 5 to 9.
The clicking would start out fast and slow down after 5 to 10 seconds. We even hooked up a new electric fuel pump and tried that too. Made on difference.
Gary Bovee
Red Bluff, CA
1978 GMC Royale
Free "Idiot's Internet Guide for Finding GMC MotorHome Information"
www.gmcidiotsguide.com
> On Dec 8, 2013, at 8:17 PM, Ken Burton <n9cv@comcast.net> wrote:
>
>
>
> If jumpering 5 to 9 did not make it stay running run then you have a fuel pump or fuel delivery problem.
>
> With 5 jumped to 9 do you hear the fuel pump running before cranking the Onan?
>
> If the pump is running does the clicking start out fast and slow down and almost stop after 5 or 10 seconds? If it does then the pump and gas feed to it are OK.
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
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Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Onan carb swap [message #232682 is a reply to message #232680] |
Mon, 09 December 2013 07:26 |
gcbgold
Messages: 60
Registered: August 2012
Karma: -1
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Member |
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Ken,
I pulled the carb off my 6k that run great and put it on it. Acted the same way. Starts and barely runs for 6 seconds and dies. I have tried starting it using the stock points and condenser and then trying the Pertronix electronic ignition to see if I had a points and condenser problem. Who knows when the points and condenser have been changed. It ran the same way with the electric ignition.
Gary Bovee
Red Bluff, CA
1978 GMC Royale
Free "Idiot's Internet Guide for Finding GMC MotorHome Information"
www.gmcidiotsguide.com
> On Dec 9, 2013, at 3:45 AM, Ken Burton <n9cv@comcast.net> wrote:
>
>
>
> Based on those symptoms, I suspect that the needle and seat in the carb is sticking or more likely it is clogged / restricted. This is not allowing full fuel flow to the carb float bowl.
>
> I would pull the carb, turn it over and remove the bowl. Be careful to observe how the float, pivot pin and needle valve are assembled. Remove the pivot pin, float, and needle valve.
>
> Clean the tip of the needle valve with carb cleaner and use some spray carb cleaner to clean the seat. Blow carb cleaner back through the seat an out through the gasoline input connection where the gasoline hose is attached. Reassemble the needle seat and float,
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