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| [GMCnet] Onan Issue [message #259955] |
Sun, 24 August 2014 19:50  |
Arthur Mansfield
Messages: 290
Registered: April 2010
Karma: 0
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Senior Member |
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I have worked on my Onan several times. I changed the points, fuel pump and filter, cleaned the carb. The Onan runs for hours with no issues when not driving. Once I drive for a couple of hours the Onan will not run right if at all. It surges and stops when driving. I just got back from a long trip. I checked the Onan the next day after the trip an it ran fine yet it would not run hardly at all when I tried to use it when stopped to eat or when it got hot in the RV. I have tried a different coil and it did the same thing on another trip. We generally have 2 cats and my wife gets up set if it gets over 85 in the RV. My dash AC is worthless so I would like to be able to run the house AC on hot days.
Since it will run ok for about 1.5 to 2 hour for the start of a trip, I wonder if gas in the tank has warmed up and is creating the problem. I tired to adjust the carb when the generator is acting up. I could not get it smooth out. If I had thought about it at the time, I would have change the coil to see if that helps.
I had another smaller Onan generator. Are the control boards the same on a 4KW as a 7KW generator. If so I will change the control board and see what that does. I guess the other thing could be carbon in the heads and the running temperature has gone up on the road and is causing the problem. I just do not know were to start. I know it runs better since I replaced the fuel pump a filter points and coil when running off the road.
Thanks
Art & Doris
76 EL
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| Re: [GMCnet] Onan Issue [message #259966 is a reply to message #259955] |
Sun, 24 August 2014 21:37  |
sgltrac
Messages: 2797
Registered: April 2011
Karma: 1
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I think that if it only acts up when driving its likely a fuel delivery issue. Try plumbing the fuel from a can on the bumper and see if problem stops?
Todd Sullivan
Sully
77 royale
Seattle
> On Aug 24, 2014, at 5:50 PM, 1104agm wrote:
>
> I have worked on my Onan several times. I changed the points, fuel pump and filter, cleaned the carb. The Onan runs for hours with no issues when not driving. Once I drive for a couple of hours the Onan will not run right if at all. It surges and stops when driving. I just got back from a long trip. I checked the Onan the next day after the trip an it ran fine yet it would not run hardly at all when I tried to use it when stopped to eat or when it got hot in the RV. I have tried a different coil and it did the same thing on another trip. We generally have 2 cats and my wife gets up set if it gets over 85 in the RV. My dash AC is worthless so I would like to be able to run the house AC on hot days.
>
> Since it will run ok for about 1.5 to 2 hour for the start of a trip, I wonder if gas in the tank has warmed up and is creating the problem. I tired to adjust the carb when the generator is acting up. I could not get it smooth out. If I had thought about it at the time, I would have change the coil to see if that helps.
>
> I had another smaller Onan generator. Are the control boards the same on a 4KW as a 7KW generator. If so I will change the control board and see what that does. I guess the other thing could be carbon in the heads and the running temperature has gone up on the road and is causing the problem. I just do not know were to start. I know it runs better since I replaced the fuel pump a filter points and coil when running off the road.
>
> Thanks
>
> Art & Doris
> 76 EL
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Sully
77 Royale basket case.
Future motorhome land speed record holder(bucket list)
Seattle, Wa.
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| Re: [GMCnet] Onan Issue [message #259985 is a reply to message #259955] |
Mon, 25 August 2014 02:27 |
midlf
Messages: 2212
Registered: July 2007
Location: SE Wisc. (Palmyra)
Karma: 1
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Senior Member |
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What is the condition of the two venting systems, fill and emissions? Electric fuel pumps don't suck that well. If you have negative tank pressure the engine pump will out pull the Onan pump. Try loosening the gas cap and see if that has any effect. It's an easy and cheap test.
Steve Southworth
1974 Glacier TZE064V100150 (for workin on)
1975 Transmode TZE365V100394 (parts & spares)
Palmyra WI
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| Re: [GMCnet] Onan Issue [message #259987 is a reply to message #259970] |
Sun, 24 August 2014 22:45 |
Gary Bovee
Messages: 177
Registered: August 2008
Karma: 0
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Senior Member |
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I had a simlar problem a couple of years ago. The difference with mine was the time period before it would shut off gradually became shorter and shorter until it finally quit. I replaced the points and condenser and it ran fine after that. I think it was the condenser going bad because the points looked OK.
Gary Bovee
Red Bluff, CA
1978 Royale
www.gmcidiotsguide.com
Free "Internet Idiot's Guide for GMC MotorHome Information"
For MAC, iPad & iPod users - http://iTunes.apple.com/us/book/internet-idiots-guide-for/id623353780?mt=11
> On Aug 24, 2014, at 8:09 PM, A. wrote:
>
> Arthur Mansfield wrote on Sun, 24 August 2014 19:50
>> I have worked on my Onan several times. I changed the points, fuel pump and filter, cleaned the carb. The Onan runs for hours with no issues
>> when not driving. Once I drive for a couple of hours the Onan will not run right if at all. It surges and stops when driving. I just got back from
>> a long trip. I checked the Onan the next day after the trip an it ran fine yet it would not run hardly at all when I tried to use it when stopped
>> to eat or when it got hot in the RV. I have tried a different coil and it did the same thing on another trip. We generally have 2 cats and my wife
>> gets up set if it gets over 85 in the RV. My dash AC is worthless so I would like to be able to run the house AC on hot days.
>>
>> Since it will run ok for about 1.5 to 2 hour for the start of a trip, I wonder if gas in the tank has warmed up and is creating the problem. I
>> tired to adjust the carb when the generator is acting up. I could not get it smooth out. If I had thought about it at the time, I would have
>> change the coil to see if that helps.
>>
>> I had another smaller Onan generator. Are the control boards the same on a 4KW as a 7KW generator. If so I will change the control board and see
>> what that does. I guess the other thing could be carbon in the heads and the running temperature has gone up on the road and is causing the
>> problem. I just do not know were to start. I know it runs better since I replaced the fuel pump a filter points and coil when running off the
>> road.
>>
>> Thanks
>>
>> Art & Doris
>> 76 EL
> http://gmc.mybirdfeeder.net/GMCforum/index.php?t=msg&goto=179089&rid=2083#msg_179089
> --
> '73 23' Sequoia For Sale
> '73 23' CanyonLands For Sale
> Upper Alabama
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| Re: [GMCnet] Onan Issue [message #260004 is a reply to message #259987] |
Mon, 25 August 2014 09:31 |
powerjon
Messages: 2446
Registered: January 2004
Karma: 5
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Senior Member |
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Art,
The Onan draws it fuel from the rear of your 2 fuel tanks which is your main fuel tank with the aux. fuel tank in the front on GMC finished coaches. On coaches finished by other when shipped as a transmode the up fitters most of the time tapped into the fuel coming out of the rear tank.
You say that this condition starts after you have been driving for a couple of hours. Your fuel level might be at or near where you fuel pickup in located on the main tank causing you to suck vapor instead of gas. The nozzle on the tank is located on driver side rear top and extends down into the tank. It is supposed to leave enough fuel in the tank so that you are not stranded if you run the generator for long periods. Todays fuel is terrible and will boil in the tanks going down the road on hot days causing vapor lock and your Onan is no different, especially when your fuel level is near the fuel pickup level and you're setting at a rest area or parking area. When you're running the Onan when stopped setting overnight the fuel in the tanks is most likely near ambient temperature and the Onan runs fine because the fuel is cool.
JR Wright
78 Buskirk Stretch
75 Avion
Michigan
On Aug 24, 2014, at 11:45 PM, Gary Bovee wrote:
> I had a simlar problem a couple of years ago. The difference with mine was the time period before it would shut off gradually became shorter and shorter until it finally quit. I replaced the points and condenser and it ran fine after that. I think it was the condenser going bad because the points looked OK.
>
> Gary Bovee
> Red Bluff, CA
> 1978 Royale
> www.gmcidiotsguide.com
> Free "Internet Idiot's Guide for GMC MotorHome Information"
> For MAC, iPad & iPod users - http://iTunes.apple.com/us/book/internet-idiots-guide-for/id623353780?mt=11
>
>> On Aug 24, 2014, at 8:09 PM, A. wrote:
>>
>> Arthur Mansfield wrote on Sun, 24 August 2014 19:50
>>> I have worked on my Onan several times. I changed the points, fuel pump and filter, cleaned the carb. The Onan runs for hours with no issues
>>> when not driving. Once I drive for a couple of hours the Onan will not run right if at all. It surges and stops when driving. I just got back from
>>> a long trip. I checked the Onan the next day after the trip an it ran fine yet it would not run hardly at all when I tried to use it when stopped
>>> to eat or when it got hot in the RV. I have tried a different coil and it did the same thing on another trip. We generally have 2 cats and my wife
>>> gets up set if it gets over 85 in the RV. My dash AC is worthless so I would like to be able to run the house AC on hot days.
>>>
>>> Since it will run ok for about 1.5 to 2 hour for the start of a trip, I wonder if gas in the tank has warmed up and is creating the problem. I
>>> tired to adjust the carb when the generator is acting up. I could not get it smooth out. If I had thought about it at the time, I would have
>>> change the coil to see if that helps.
>>>
>>> I had another smaller Onan generator. Are the control boards the same on a 4KW as a 7KW generator. If so I will change the control board and see
>>> what that does. I guess the other thing could be carbon in the heads and the running temperature has gone up on the road and is causing the
>>> problem. I just do not know were to start. I know it runs better since I replaced the fuel pump a filter points and coil when running off the
>>> road.
>>>
>>> Thanks
>>>
>>> Art & Doris
>>> 76 EL
>> http://gmc.mybirdfeeder.net/GMCforum/index.php?t=msg&goto=179089&rid=2083#msg_179089
>> --
>> '73 23' Sequoia For Sale
>> '73 23' CanyonLands For Sale
>> Upper Alabama
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
> _______________________________________________
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J.R. Wright
GMC GreatLaker
GMC Eastern States
GMCMI
78 30' Buskirk Stretch
75 Avion Under Reconstruction
Michigan
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| Re: [GMCnet] Onan Issue [message #260033 is a reply to message #260004] |
Mon, 25 August 2014 13:21 |
Arthur Mansfield
Messages: 290
Registered: April 2010
Karma: 0
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Senior Member |
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Thanks everyone. I already checked and my gas cap does not seal tight. The Onan still will not run correctly after I have been on the road and refilled the tank. I tried to run the generator after refueling to run the AC unit. It surged and I had to shut it off.
I am being to think it is the temperature of the gas is the problem. I tried to adjust the carb when it was hot and not running correctly. It did not help. Once everything cooled off the generator ran find except I had the carb very very rich.
Thanks
Art
On Aug 25, 2014, at 9:31 AM, John Wright wrote:
> Art,
> The Onan draws it fuel from the rear of your 2 fuel tanks which is your main fuel tank with the aux. fuel tank in the front on GMC finished coaches. On coaches finished by other when shipped as a transmode the up fitters most of the time tapped into the fuel coming out of the rear tank.
>
>
>
> You say that this condition starts after you have been driving for a couple of hours. Your fuel level might be at or near where you fuel pickup in located on the main tank causing you to suck vapor instead of gas. The nozzle on the tank is located on driver side rear top and extends down into the tank. It is supposed to leave enough fuel in the tank so that you are not stranded if you run the generator for long periods. Todays fuel is terrible and will boil in the tanks going down the road on hot days causing vapor lock and your Onan is no different, especially when your fuel level is near the fuel pickup level and you're setting at a rest area or parking area. When you're running the Onan when stopped setting overnight the fuel in the tanks is most likely near ambient temperature and the Onan runs fine because the fuel is cool.
>
> JR Wright
> 78 Buskirk Stretch
> 75 Avion
> Michigan
>
> On Aug 24, 2014, at 11:45 PM, Gary Bovee wrote:
>
>> I had a simlar problem a couple of years ago. The difference with mine was the time period before it would shut off gradually became shorter and shorter until it finally quit. I replaced the points and condenser and it ran fine after that. I think it was the condenser going bad because the points looked OK.
>>
>> Gary Bovee
>> Red Bluff, CA
>> 1978 Royale
>> www.gmcidiotsguide.com
>> Free "Internet Idiot's Guide for GMC MotorHome Information"
>> For MAC, iPad & iPod users - http://iTunes.apple.com/us/book/internet-idiots-guide-for/id623353780?mt=11
>>
>>> On Aug 24, 2014, at 8:09 PM, A. wrote:
>>>
>>> Arthur Mansfield wrote on Sun, 24 August 2014 19:50
>>>> I have worked on my Onan several times. I changed the points, fuel pump and filter, cleaned the carb. The Onan runs for hours with no issues
>>>> when not driving. Once I drive for a couple of hours the Onan will not run right if at all. It surges and stops when driving. I just got back from
>>>> a long trip. I checked the Onan the next day after the trip an it ran fine yet it would not run hardly at all when I tried to use it when stopped
>>>> to eat or when it got hot in the RV. I have tried a different coil and it did the same thing on another trip. We generally have 2 cats and my wife
>>>> gets up set if it gets over 85 in the RV. My dash AC is worthless so I would like to be able to run the house AC on hot days.
>>>>
>>>> Since it will run ok for about 1.5 to 2 hour for the start of a trip, I wonder if gas in the tank has warmed up and is creating the problem. I
>>>> tired to adjust the carb when the generator is acting up. I could not get it smooth out. If I had thought about it at the time, I would have
>>>> change the coil to see if that helps.
>>>>
>>>> I had another smaller Onan generator. Are the control boards the same on a 4KW as a 7KW generator. If so I will change the control board and see
>>>> what that does. I guess the other thing could be carbon in the heads and the running temperature has gone up on the road and is causing the
>>>> problem. I just do not know were to start. I know it runs better since I replaced the fuel pump a filter points and coil when running off the
>>>> road.
>>>>
>>>> Thanks
>>>>
>>>> Art & Doris
>>>> 76 EL
>>> http://gmc.mybirdfeeder.net/GMCforum/index.php?t=msg&goto=179089&rid=2083#msg_179089
>>> --
>>> '73 23' Sequoia For Sale
>>> '73 23' CanyonLands For Sale
>>> Upper Alabama
>>> _______________________________________________
>>> GMCnet mailing list
>>> Unsubscribe or Change List Options:
>>> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>> _______________________________________________
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>
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| Re: [GMCnet] Onan Issue [message #260067 is a reply to message #260033] |
Mon, 25 August 2014 19:10 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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Arthur Mansfield wrote on Mon, 25 August 2014 14:21Thanks everyone. I already checked and my gas cap does not seal tight. The Onan still will not run correctly after I have been on the road and refilled the tank. I tried to run the generator after refueling to run the AC unit. It surged and I had to shut it off.
I am being to think it is the temperature of the gas is the problem. I tried to adjust the carb when it was hot and not running correctly. It did not help. Once everything cooled off the generator ran find except I had the carb very very rich.
Thanks
Art
Art,
I don't know how you can check this if you only have one, but I had a very similar issue. Fortunately, I have a complete spare Onan. (Well, it is still complete, but I have not screwed all the parts back on yet.) It ran rich and there did not seem to be much I could do about it. I fouled out a brand new pair of plugs. So, I started checking things. I got the float out and it seemed heavy..... so I compared it to the other and it was about 1/2 gram heavier.
This should be a fade to grey and a note - Some Days Later
After doing a lot of useless things, the new float came in the mail. I set it up per the manual and started if up and after setting it to frequency at load, she decided to be the wonderful old Onan I knew.
Mine is a BF. I can provide the exact weight of the float for an LMB carburetor if that might help.
Decades ago I had dirt bikes. They used to sink floats all the time. Sometime you could see the crack and solder it.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: [GMCnet] Onan Issue [message #260073 is a reply to message #259955] |
Mon, 25 August 2014 20:08 |
lotsofspareparts
Messages: 726
Registered: May 2014
Location: Arlington, WA
Karma: -9
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Senior Member |
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What color is the insulator on your spark plugs after running your generator under load?
Run for a while under load shut off the device providing the load and immediately after kill the genset.
Pull plugs and report on the insulator color, IE: white, tan, beige, light brown, brown, dark brown, black.
Pictures will help.
Jared
Jared & Tina Lazaron + 14yr old Daughter.....
77 Eleganza II "Recherché".....
73 Canyon Lands 230 "Elephant"
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| Re: [GMCnet] Onan Issue [message #260098 is a reply to message #260073] |
Tue, 26 August 2014 00:02 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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Senior Member |
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You might jump on the board 5-9 and activate the fuel pump.
I have taken a magic marker and put it on the side and also have a pair
small alligator clips.
I feel it is an necessary tool.
Also, use a pair of pliers to back off the screw that is impossible to
loosen the cover.
On Mon, Aug 25, 2014 at 6:08 PM, Jared wrote:
> What color is the insulator on your spark plugs after running your
> generator under load?
>
> Run for a while under load shut off the device providing the load and
> immediately after kill the genset.
>
> Pull plugs and report on the insulator color, IE: white, tan, beige, light
> brown, brown, dark brown, black.
>
> Pictures will help.
>
> Jared
> --
> Jared & Tina Lazaron + 7yr old Daughter.
>
> 77 Eleganza II "Recherché" Winterfeldt 455, Holley ProJection, Doug
> Thorley Headers, 3in exhaust, Switch Pitch, Alcoas, ONAN 6.5 Emerald
> series, CMC
> Restoration
>
> GO SEAHAWKS!!
>
> Arlington, WA 98223
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--
Jim Kanomata
Applied/GMC, Fremont,CA
jimk@appliedairfilters.com
http://www.appliedgmc.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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