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| [GMCnet] Onan question [message #96939] |
Mon, 23 August 2010 16:05  |
bhayes
Messages: 263
Registered: March 2010
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We've been having an issue with the Onan in our newly purchased '76
Eleganza. It will run under load for about 30-60 minutes, then stumble and
stall. No amount of cranking will get it to start again until at least 30+
minutes have passed. I suspect a fuel delivery issue or that it is
overheating, and was wondering if there is a thermal shutdown switch
somewhere that shuts it down to prevent overheating. The problem seems to
occur more often if the outside temperature is above 85 degrees, and it
occurs even when the fuel tank is full. It also has plenty of oil, so I
don't think it's the low oil switch.
Bryan Hayes
'76 Eleganza II
Salt Lake City, Utah
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Bryan Hayes
'76 Eleganza II
Salt Lake City, Utah
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| Re: [GMCnet] Onan question [message #96941 is a reply to message #96939] |
Mon, 23 August 2010 16:23  |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
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| Bryan Hayes wrote on Mon, 23 August 2010 15:05 |
We've been having an issue with the Onan in our newly purchased '76
Eleganza. It will run under load for about 30-60 minutes, then stumble and
stall. No amount of cranking will get it to start again until at least 30+
minutes have passed. I suspect a fuel delivery issue or that it is
overheating, and was wondering if there is a thermal shutdown switch
somewhere that shuts it down to prevent overheating. The problem seems to
occur more often if the outside temperature is above 85 degrees, and it
occurs even when the fuel tank is full. It also has plenty of oil, so I
don't think it's the low oil switch.
Bryan Hayes
'76 Eleganza II
Salt Lake City, Utah
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There's no temperature shut down on these models. It sounds like a fuel delivery problem but it could also be several other things. If you have a primer button, you can try to hold it in while trying to restart and see if that works--it bypasses the board and will run the pump. It can also be the filter in the pump. If you don't have a primer button, remove the cover from the control board and jumper terminals 9 and 5. That will bypass the control board and run the pump directly.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: [GMCnet] Onan question [message #96943 is a reply to message #96939] |
Mon, 23 August 2010 16:37 |
emerystora
Messages: 4442
Registered: January 2004
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On Aug 23, 2010, at 3:05 PM, Bryan Hayes wrote:
> We've been having an issue with the Onan in our newly purchased '76
> Eleganza. It will run under load for about 30-60 minutes, then stumble and
> stall. No amount of cranking will get it to start again until at least 30+
> minutes have passed. I suspect a fuel delivery issue or that it is
> overheating, and was wondering if there is a thermal shutdown switch
> somewhere that shuts it down to prevent overheating. The problem seems to
> occur more often if the outside temperature is above 85 degrees, and it
> occurs even when the fuel tank is full. It also has plenty of oil, so I
> don't think it's the low oil switch.
>
> Bryan Hayes
> '76 Eleganza II
> Salt Lake City, Utah
>
It might be something as simple as a poor connection on the fuse clip in terminals on the control board. When it gets hot these can lose contact but when it cools it will work again.
.
Normally I would say to jumper terminals 9 to 5 to see if it will run. But in this case jumper terminals 9 to 11. Do this because that bypasses the control board entirely whereas 9 to 5 still leaves the fuse in the circuit.
If it runs then turn it off and jumper 9 to 5 and see if it still runs. You know its the control board but you don't know what it is on the board. If it runs with 9 to 11 but it doesn't run with 9 to 5 you can be pretty sure its the fuse or the fuse connector.
Emery Stora
77 Kingsley
Santa Fe, NM
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| Re: [GMCnet] Onan question [message #96947 is a reply to message #96945] |
Mon, 23 August 2010 16:49 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
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And if all that doesn't locate the problem, start thinking "heat sensitive
coil or condenser". The easiest way to check that is with a spark indicator
light ($2.99 at Harbor Freight). While the Onan is running OK, test the
light so you'll know what a good spark looks like (probably very weak).
Then when it's just died and won't start, use the indicator light to see if
you've still got spark.
Ken H.
Americus, GA
'76 X-Birchaven w/Cad500/Howell EFI+ & EBL
No Onan!
www.gmcwipersetc.com
On Mon, Aug 23, 2010 at 5:40 PM, Emery Stora <emerystora@mac.com> wrote:
> On Aug 23, 2010, at 3:23 PM, Bob de Kruyff wrote:
> > There's no temperature shut down on these models. It sounds like a fuel
> delivery problem...
>
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: [GMCnet] Onan question [message #96951 is a reply to message #96945] |
Mon, 23 August 2010 17:33 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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""Bob -- I hadn't read your message before sending my reply on this topic.
The only thing one has to check before jumping 9 to 5 is that the fuse on the board works properly. If the fuse is blown or the connections to the fuse loose then 9 to 5 will not do anything. 9 to 11 will test it but that takes the fuse out of the circuit. 9 to 5 is safer but you must know that the fuse is good.
""
Good catch--I forgot all about the fuse!
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: [GMCnet] Onan question [message #96986 is a reply to message #96939] |
Mon, 23 August 2010 21:42 |
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ljdavick
Messages: 3548
Registered: March 2007
Location: Fremont, CA
Karma: -3
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Fuel filter?
Ljdavick at comcast.net
On Aug 23, 2010, at 2:05 PM, Bryan Hayes <bhayes@byu.net> wrote:
> We've been having an issue with the Onan in our newly purchased '76
> Eleganza. It will run under load for about 30-60 minutes, then
> stumble and
> stall. No amount of cranking will get it to start again until at
> least 30+
> minutes have passed. I suspect a fuel delivery issue or that it is
> overheating, and was wondering if there is a thermal shutdown switch
> somewhere that shuts it down to prevent overheating. The problem
> seems to
> occur more often if the outside temperature is above 85 degrees, and
> it
> occurs even when the fuel tank is full. It also has plenty of oil,
> so I
> don't think it's the low oil switch.
>
> Bryan Hayes
> '76 Eleganza II
> Salt Lake City, Utah
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
_______________________________________________
GMCnet mailing list
List Information and Subscription Options:
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Larry Davick
A Mystery Machine
1976(ish) Palm Beach
Fremont, Ca
Howell EFI + EBL + Electronic Dizzy
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| Re: [GMCnet] Onan question [message #97144 is a reply to message #96939] |
Wed, 25 August 2010 10:13 |
bhayes
Messages: 263
Registered: March 2010
Karma: 1
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Senior Member |
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Thanks for all the comments, everyone. I had a chance to test the generator out last night. The temperature was cool enough such that the generator wouldn't stall, but it did get hot enough to refuse to start after I shut it down. No amount of cranking would get it to start until I jumpered terminals 9 and 11 or 9 and 5. Jumpering either one caused the fuel pump to run, after which the generator started right up. Shutting it down and removing the jumper would result in it not starting again. I repeated this process several times.
Is there a way to troubleshoot the control board, or am I better off replacing it? Does the primer button that many people install bypass the control board and run the fuel pump? I have a primer button that I installed next to the switch inside the coach last night, but haven't had a chance to test it out with the generator hot. I'm thinking the primer button may be a good short-term solution for restarting the genset when it stalls if it bypasses the control board.
Bryan Hayes
'76 Eleganza II
Salt Lake City, Utah
Bryan Hayes
'76 Eleganza II
Salt Lake City, Utah
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| Re: [GMCnet] Onan question [message #97149 is a reply to message #97144] |
Wed, 25 August 2010 10:23 |
emerystora
Messages: 4442
Registered: January 2004
Karma: 13
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Yes, the primer button does start the fuel pump to prime the engine but if your Onan will not work without jumpering the control board then you have a bad board and it will not run even if you prime it.
You can have Duane Simmons rebuild your control board. It used to cost about $100 but I don't know his current price.
Or, you can order one from Jim Kanomata at appliedgmc.com
I was going to look it up for you but his site would not connect this morning.
Emery Stora
On Aug 25, 2010, at 9:13 AM, Bryan Hayes wrote:
>
>
> Thanks for all the comments, everyone. I had a chance to test the generator out last night. The temperature was cool enough such that the generator wouldn't stall, but it did get hot enough to refuse to start after I shut it down. No amount of cranking would get it to start until I jumpered terminals 9 and 11 or 9 and 5. Jumpering either one caused the fuel pump to run, after which the generator started right up. Shutting it down and removing the jumper would result in it not starting again. I repeated this process several times.
>
> Is there a way to troubleshoot the control board, or am I better off replacing it? Does the primer button that many people install bypass the control board and run the fuel pump? I have a primer button that I installed next to the switch inside the coach last night, but haven't had a chance to test it out with the generator hot. I'm thinking the primer button may be a good short-term solution for restarting the genset when it stalls if it bypasses the control board.
>
> Bryan Hayes
> '76 Eleganza II
> Salt Lake City, Utah
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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| Re: [GMCnet] Onan question [message #97154 is a reply to message #97144] |
Wed, 25 August 2010 10:45 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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""Is there a way to troubleshoot the control board, or am I better off replacing it? Does the primer button that many people install bypass the control board and run the fuel pump? I have a primer button that I installed next to the switch inside the coach last night, but haven't had a chance to test it out with the generator hot. I'm thinking the primer button may be a good short-term solution for restarting the genset when it stalls if it bypasses the control board.
""
Did you get a chance to check the fuse as Emery mentioned? These boards can get troublesome as they age and the various solder joints and relays get tired. If you're up to it a new board can be had for a bit less than $150 and it's an easy swap. As far as the primer circuit, it may help to get it started, but the minute you release it the engine will stop based on your current symptoms. When you do get it all squared away, I would add the primer function since it really reduces the crank times after sitting for a bit.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: [GMCnet] Onan question [message #97157 is a reply to message #97154] |
Wed, 25 August 2010 11:09 |
bhayes
Messages: 263
Registered: March 2010
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Oddly enough the engine continues to run when I remove the jumper. It just won't start after I stop it or it stalls until it has a chance to cool down, or I jumper the terminals. The fuse appears fine.
I took a look at JimK's replacement boards. He has new boards as well as refurbished original boards. Any preference on what I should use?
Bryan Hayes
'76 Eleganza II
Salt Lake City, Utah
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| Re: [GMCnet] Onan question [message #97159 is a reply to message #97157] |
Wed, 25 August 2010 11:12 |
Dennis S
Messages: 3046
Registered: November 2005
Karma: 2
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Bryan
Follow the wire over the top of the Onan that supplies power to the fuel pump. There is usually a spice near the top center-- clean this connection and the one at the pump and at the circuit board,
May help.
Dennis Sexton
73 PD 230
Germantown, TN
USA
-----Original Message-----
From: Bryan Hayes <hayesnet1@gmail.com>
To: gmclist@temp.gmcnet.org
Sent: Wed, Aug 25, 2010 11:09 am
Subject: Re: [GMCnet] Onan question
Oddly enough the engine continues to run when I remove the jumper. It just
on't start after I stop it or it stalls until it has a chance to cool down, or
jumper the terminals. The fuse appears fine.
I took a look at JimK's replacement boards. He has new boards as well as
efurbished original boards. Any preference on what I should use?
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MCnet mailing list
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Dennis S
73 Painted Desert 230
Memphis TN Metro
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| Re: [GMCnet] Onan question [message #97267 is a reply to message #97144] |
Thu, 26 August 2010 07:34 |
Steven Ferguson
Messages: 3447
Registered: May 2006
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Bryan,
I have a new board and that is what you need. Jumpering 9 to 5
eliminates the board function entirely. Contact me off line if you
are interested.
On Wed, Aug 25, 2010 at 8:13 AM, Bryan Hayes <hayesnet1@gmail.com> wrote:
>
>
> Thanks for all the comments, everyone. I had a chance to test the generator out last night. The temperature was cool enough such that the generator wouldn't stall, but it did get hot enough to refuse to start after I shut it down. No amount of cranking would get it to start until I jumpered terminals 9 and 11 or 9 and 5. Jumpering either one caused the fuel pump to run, after which the generator started right up. Shutting it down and removing the jumper would result in it not starting again. I repeated this process several times.
>
> Is there a way to troubleshoot the control board, or am I better off replacing it? Does the primer button that many people install bypass the control board and run the fuel pump? I have a primer button that I installed next to the switch inside the coach last night, but haven't had a chance to test it out with the generator hot. I'm thinking the primer button may be a good short-term solution for restarting the genset when it stalls if it bypasses the control board.
>
> Bryan Hayes
> '76 Eleganza II
> Salt Lake City, Utah
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
--
Steve Ferguson
'76 EII
Sierra Vista, AZ
Urethane bushing source
www.bdub.net/ferguson/
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| Re: [GMCnet] Onan question [message #97296 is a reply to message #97267] |
Thu, 26 August 2010 11:21 |
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mike miller
Messages: 3576
Registered: February 2004
Location: Hillsboro, Oregon
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| Steven Ferguson wrote on Thu, 26 August 2010 05:34 |
... Jumpering 9 to 5 eliminates the board function entirely. ...
|
I have never heard of this one....
When adding the Pentronics module, I found a PO had jumpered the unused lower pin 6 to pin 9. As the pins are next to each other, the jumper is a very short piece of wire and on crimped on connector. Unless you are looking for it, you hardly even see it.
The Onan starts and stops with the switch on the board as well as the switch inside. The board does NOT turn off the fuel pump or ignition if the engine stops for some other reason than being turned off by a switch. It also does NOT provide any low oil pressure protection.
My Onan doesn't run if I remove this "6 to 9" jumper.
The 6 to 9 jumper is "better" than a 5 to 9 jumper as it leaves the start/stop functions active. But would be easier to forget that it was done.... most likely how I ended up with it.
It is on my list of things to fix... I have to VERY careful how I use the Onan until then.
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 question [message #97436 is a reply to message #97296] |
Fri, 27 August 2010 07:24 |
Steven Ferguson
Messages: 3447
Registered: May 2006
Karma: 0
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Mike,
A remanufactured ckt board from Duane used to be $100
If you need it, let me know.
Steve
On Thu, Aug 26, 2010 at 9:21 AM, Mike Miller <m000035@gmail.com> wrote:
>
>
> Steven Ferguson wrote on Thu, 26 August 2010 05:34
>> ... Jumpering 9 to 5 eliminates the board function entirely. ...
>
>
> I have never heard of this one....
>
> When adding the Pentronics module, I found a PO had jumpered the unused lower pin 6 to pin 9. As the pins are next to each other, the jumper is a very short piece of wire and on crimped on connector. Unless you are looking for it, you hardly even see it.
>
> The Onan starts and stops with the switch on the board as well as the switch inside. The board does NOT turn off the fuel pump or ignition if the engine stops for some other reason than being turned off by a switch. It also does NOT provide any low oil pressure protection.
>
> My Onan doesn't run if I remove this "6 to 9" jumper.
>
> The 6 to 9 jumper is "better" than a 5 to 9 jumper as it leaves the start/stop functions active. But would be easier to forget that it was done.... most likely how I ended up with it.
>
> It is on my list of things to fix... I have to VERY careful how I use the Onan until then.
> --
> Mike Miller
> `73 26' X Painted D.
> `78 23' Birchaven
> Hillsboro, OR
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
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--
Steve Ferguson
'76 EII
Sierra Vista, AZ
Urethane bushing source
www.bdub.net/ferguson/
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