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Onan Carb Problems


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#1 robintwist OFFLINE  

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Posted September 09, 2010 - 06:17 AM

I have been having trouble setting up the carb on my 1855A, I first noticed a problem when the crank case filled with fuel overnight, I have striped the carb and cleaned it, drained and refilled the oil, it still has this problem meaning I have to turn off the fuel after each use (if I could use it).
The carb is filling with fuel as normal but when the engine is running it empties the bowl and stops, there does'nt seem to be any fuel getting to the carb to fill the bowl once the engine is running, I have checked the fuel pump (external type) and it pumps very well.
Got to say I am getting very frustrated with it, I priced a new carb from cumminsonan they want £311.00 $479.00 for one, or £104.00 $160.00 for a repair kit, I have searched ebay etc but no luck, any ideas from you experienced GT owners?
Cheers Robin

#2 olcowhand ONLINE  

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Posted September 09, 2010 - 08:40 AM

Your fuel pump diaphram has a hole in it & pumping all the fuel into the crankcase. Your pump is separate from the carb? Some DD carbs have the fuel pump made to the side of the carb. Either type will fill crankcase when the diaphram ruptures. The best thing you can do is to dump the vacuum fuel pump & install an electric unit. Get a low pressure/low volume unit. I'm using a Mr Gasket model 42S. It is 2 to 3.5psi & works well with these carbs as long as you have a good float & needle/seat. One advantage is after period of non use, the carb will evaporate the fuel & the vacuum pumps take some time to fill during cranking over, which is hard on the starter. With electric pump, turn key on, give it a few seconds & carb is full, then start her up. Below is link to this pump info. You can buy at most automotive parts stores.
MICRO ELECTRIC FUEL PUMP-42GPH (42S) | electric fuel pumps |

#3 robintwist OFFLINE  

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Posted September 09, 2010 - 09:17 AM

olcowhand, thanks for the info, if as you say the diaphram has a hole in it, would this mean that even though the pump does appear to work when the fuel line is removed from the carb it will not keep up with the flow required once it is connected and under a little pressure?

#4 NUTNDUN OFFLINE  

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Posted September 09, 2010 - 10:36 AM

would this mean that even though the pump does appear to work when the fuel line is removed from the carb it will not keep up with the flow required once it is connected and under a little pressure?


I think you got it. When the fuel line is off and there is no resistance the fuel will flow the easiest path, once you hook the line up and it has to flow into the float bowl through the needle it creates more resistance then what the hole in the diaphragm does. I know if the fuel pump craps out on my 1655 I will be doing the electric fuel pump and I may not even wait until then. You definitely don't have a carb problem.

#5 NUTNDUN OFFLINE  

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Posted September 09, 2010 - 10:36 AM

I wanted to add that you should post in the member introduction forum since you are our first UK member :D

#6 olcowhand ONLINE  

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Posted September 09, 2010 - 11:31 AM

Yes, I forgot my manners...:welcome: to GTT! And when a diaphram is bad, the vacuum side of the pump will be full of fuel & keep pump from working properly.

#7 mjodrey OFFLINE  

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Posted September 09, 2010 - 12:12 PM

robintwist :welcometogttalk:glad to have you here.

#8 ducky ONLINE  

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Posted September 09, 2010 - 12:34 PM

Hi Robin
Welcome to GTtalk.
I think Daniel has you zeroed in on your problem.
Yes, Electric fuel pumps work very well along with easier starting.

#9 robintwist OFFLINE  

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Posted September 09, 2010 - 04:20 PM

I want to say thankyou to you all for your advice and your welcome to me to GTT, I am delighted that olcowhand replied to me as I have been a regular viewer on this site looking for advice about my 1855A and onan engines, He does seem to be the daddy where this marque is concerned ! I have to say that both Snapper tractors and onan engines are quite rare in the UK (usually Briggs), I have seen a few of the smaller Snappers here for sale but they seem to be in the south of the UK and I am in the farming county of Cheshire in the north.
I didn't realise I was your first UK member, if this is so I must now go down in history as far as this site is concerned!
Just to let you know I have ordered a facit 1.5 - 4.0 psi fuel pump for the Snapper and I will let you know how I go on.
Cheers to all.
Robin

#10 olcowhand ONLINE  

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Posted September 09, 2010 - 04:32 PM

IF the electric fuel pump does overpower your float/needle assembly, you can add a pressure regulator to drop it down to as low as 1psi. I've never had a problem with the Onan carbs with the low psi pumps though. On my Bush Hog tractor that I installed a Wisconsin TJD, I had to use a regulator as it's float couldn't handle the electric pump. You should be fine.
Yes, you are the 1st UK member!

:smiley-flag013::smiley-flag013::smiley-flag013::smiley-flag013::smiley-flag013::smiley-flag013::smiley-flag013::smiley-flag013::smiley-flag013::smiley-flag013::smiley-flag013::smiley-flag013::smiley-flag013:

#11 mjodrey OFFLINE  

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Posted September 09, 2010 - 06:02 PM

Robin,where in the U.K. do you live ? I have a good buddy who lives in Leicester,and it's funny because his name is Robbin too only with two b's.

#12 olcowhand ONLINE  

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Posted September 09, 2010 - 08:16 PM

Used to be a great guy that goes by "Mith" on forums from the UK. Forget his last name at the moment, first name Jim. He's been AWOL from the forums for quite some time. He's from south UK though.

#13 caseguy OFFLINE  

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Posted September 09, 2010 - 09:15 PM

:wave: Sorry to be the latecomer, but welcome to the forum robintwist! great to have you here!

#14 ducky ONLINE  

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Posted September 09, 2010 - 09:54 PM

Just a little nosy.
Are there many Snappers and Masseys over there?
No I am not coming over and buying them up.
Just curious.
I uploaded a serial to build date for Masseys to the Massey manual section and would also like to know any serials you may have to verify that information.
I am still in search of Snapper Serial to Build Dates.
Any Info would be greatly appreciated.
Again welcome to GTtalk and congrats on being our first UK member.

#15 bhts OFFLINE  

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Posted September 09, 2010 - 10:31 PM

:welcometogttalk:

Alot of good info here and people willing to share.




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