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Onan Carb Swap


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#1 fedora OFFLINE  

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Posted January 05, 2014 - 05:14 PM

Hello all,

 

After weeks of searching, the $800 carb came in for our 5K Onan generator at work. I swapped out the broken one with the new one. I set the jet to 1 1/2 turns out, and all I can get out of it is a loud pop with a small flame coming out of the carb. All the fuel and what I assume are vacuum lines and linkages are hooked up exactly like the old one.

 

This unit ran flawless before the plastic choke linkage broke on the old carb.

 

I've never worked with an Onan carb before, and it seems like an odd system...what do you all think I should try next?

 

Thanks,

Fedora

 



#2 ol' stonebreaker OFFLINE  

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Posted January 06, 2014 - 09:50 AM

Sounds like possibly an intake valve problem.
Mike

#3 fedora OFFLINE  

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Posted January 06, 2014 - 05:49 PM

I pulled the head off today and cranked it over, the valves seem to work properly. Its getting great spark, but it still backfires through the carb on choke and auto choke, when the choke is off, I get nothing. It seems like it may be getting too much fuel, after about 3-4 seconds of cranking, it starts to spit fuel out of the mouth of the carb.

 

I did pull the float bowl off to make sure it wasn't stuck from shipping, but it seems to be working fine,,,I hate to admit defeat and take it to somebody, but it needs to be up and running asap.



#4 New.Canadian.DB.Owner OFFLINE  

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Posted January 06, 2014 - 06:45 PM

First, did you shake the float while you had it out?  Is it leaking & full of fuel?  If so, it won't rise & close the inlet needle, thus flooding the carb.  

 

Second, did you check the spark plug?  Is it wet or dry?  Wet is flooding, dry is sucking air from someplace other than the carb.  Both result in lack of fuel to noise conversion.  

 

Third, have you checked the timing?  All the spark & fuel in the world will do you no good if the spark comes at the wrong time.



#5 fedora OFFLINE  

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Posted January 19, 2014 - 02:06 PM

I looked everything over again, and did sort of a leak down test with what I had available. I picked a few brains who are in the small engine repair business, and then threw in the towel. Turns out the governor plate was slightly askewed/bent from either the factory or shipping, and the shop we bought it from replaced/repaired it and got it running for free. He said he got it to start with the bent plate and it ran away on him, and he thought it would scatter before it shut down, lol, kinda glad I didn't get it to fire.

 

 

Thanks for all the suggestions.






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