| Re: [GMCnet] Onan Issue [message #260004 is a reply to message #259987] |
Mon, 25 August 2014 09:31   |
powerjon
Messages: 2446
Registered: January 2004
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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
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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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