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Home » Public Forums » GMCnet » Onan Carburetor SNAFU (Exploded diagram on page 13 of manual is WRONG!)
Onan Carburetor SNAFU [message #170895] Sat, 26 May 2012 16:09 Go to next message
pyolet is currently offline  pyolet   United States
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Registered: August 2006
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For those of you still nursing the Onan, thought I'd share a lesson learned.

After 3 years of my 6K Onan sitting on the garage floor (installed a Generac 55 in the MH), finally got around to prepping the old beast for use at the cabin. Decarbonized the heads, cleaned and checked everything, and built a cart out of some scrap steel and some HF wheels per the photos Davem posted. She fired to life again but for the life of me, couldn't get her to lean out without unplugging the fuel pump. Must've opened up the carb a dozen times to adjust/check everything.

Figured the carb was just worn out and was on the verge of ordering a rebuild kit from Jim K, and noticed in the photo on his website a fat, round gasket I hadn't seen during the dozen disassemblies of my carb. The diagram on page 13 of the manual, as well as my malfunctioning carb, doesn't have this gasket. Guess I dropped mine on the floor during disassembly and it rolled into that Murphy place, and upon reassembly of course I followed the schematic and it made sense since the marks on the bowl screen looked to match up with the nozzle boss.

It was only by referring to the Fuel System Trouble Diagnosis for smokes and runs rich, that the "nozzle boss gasket" is mentioned. Doph...all that fuel is sucked straight into the nozzle, bypassing the hi power jet. So I made a temp gasket from thick immersion safe thick gasket material and inserted it in the bowl between the filter screen and the nozzle boss. She runs like new now and I've just ordered the parts to convert it tri-fuel capable for the outpost.

Moral to the story, don't rely exclusively on any manual...take pictures with your cell phone of each step of disassembly, so if CRS hits you like it hits me a lot, you can put it back together the way it came apart. Also, do all those graveyard Onan's have more untold secret fixes up their sleeves? It is one tough machine and might deserve a second look if you've got one you're using a doorstop. FWIW. Woody.
Re: [GMCnet] Onan Carburetor SNAFU [message #170897 is a reply to message #170895] Sat, 26 May 2012 17:08 Go to previous message
sgltrac is currently offline  sgltrac   United States
Messages: 2797
Registered: April 2011
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Senior Member
I had a similar experience with my Onan carb. My issue was with the screen in the float bowl. It was giving me fits until I figured out that it was interfering with the operation of the float. Removed it and no more issues.

Sully
77 royale

Sent from my i slack

On May 26, 2012, at 2:09 PM, Woody <jal747@mac.com> wrote:

>
>
> For those of you still nursing the Onan, thought I'd share a lesson learned.
>
> After 3 years of my 6K Onan sitting on the garage floor (installed a Generac 55 in the MH), finally got around to prepping the old beast for use at the cabin. Decarbonized the heads, cleaned and checked everything, and built a cart out of some scrap steel and some HF wheels per the photos Davem posted. She fired to life again but for the life of me, couldn't get her to lean out without unplugging the fuel pump. Must've opened up the carb a dozen times to adjust/check everything.
>
> Figured the carb was just worn out and was on the verge of ordering a rebuild kit from Jim K, and noticed in the photo on his website a fat, round gasket I hadn't seen during the dozen disassemblies of my carb. The diagram on page 13 of the manual, as well as my malfunctioning carb, doesn't have this gasket. Guess I dropped mine on the floor during disassembly and it rolled into that Murphy place, and upon reassembly of course I followed the schematic and it made sense since the marks on the bowl screen looked to match up with the nozzle boss.
>
> It was only by referring to the Fuel System Trouble Diagnosis for smokes and runs rich, that the "nozzle boss gasket" is mentioned. Doph...all that fuel is sucked straight into the nozzle, bypassing the hi power jet. So I made a temp gasket from thick immersion safe thick gasket material and inserted it in the bowl between the filter screen and the nozzle boss. She runs like new now and I've just ordered the parts to convert it tri-fuel capable for the outpost.
>
> Moral to the story, don't rely exclusively on any manual...take pictures with your cell phone of each step of disassembly, so if CRS hits you like it hits me a lot, you can put it back together the way it came apart. Also, do all those graveyard Onan's have more untold secret fixes up their sleeves? It is one tough machine and might deserve a second look if you've got one you're using a doorstop. FWIW. Woody.
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Sully 77 Royale basket case. Future motorhome land speed record holder(bucket list) Seattle, Wa.
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