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Why Is My Carb Fuel Bowl Not Filling


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#1 VillageGreenDeere OFFLINE  

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Posted October 30, 2014 - 04:51 PM

Hi,

 

I just put the onan engine back in my 318, after the oil pan replacement and thorough clean.  I went ahead and did my first carb clean too.  Just cleaning, no new parts, spray carb cleaner and compressed air.  My problem now is the bowl is running empty and the engine stalls.

 

The fuel pump seems to be working.  If I pull the house off the out, it shoots fuel 2 feet up when I crank it over.

 

I turned the main mix screw all the way in and then out a turn and a half, also tired a single turn out.  I fill the bowl with a cup of gas, put it back together again, turn it over and it will run for 30 seconds, then stall.  I check the bowl, and it's empty again.

 

What should I check next?  What am I missing?  Before the carb clean, I couldn't run the engine without the choke at least half closed.  Now for the 30 seconds before it drains the bowl it runs great, but then, STALLLLL.

 

Matt



#2 New.Canadian.DB.Owner OFFLINE  

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Posted October 30, 2014 - 04:54 PM

I would look at the float and the fuel inlet needle & seat.  Their job is to prevent fuel from entering the bowl, when it is full.  If they are stuck shut, or the float is miss-adjusted, then they won't let fuel enter the bowl.


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#3 HDWildBill OFFLINE  

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Posted October 30, 2014 - 05:03 PM

Before you reinstalled the carb did you do a float test?  It's a simple check. With the bowl empty blow some air into the fuel inlet.  If air passes through you have flow,  then turn the carb upside down and try to blow air into the bowl.  Air should not pass through.

 

Like NCDBO said check the float and needle and make sure they are not stuck.


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#4 KennyP ONLINE  

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Posted October 30, 2014 - 05:17 PM

Has the tank got fuel in it?  Otherwise, I would go with the needle sticking on the float! Take the top off the carb, remove the float and needle valve and crank it over to make sure you are getting fuel to the carb!


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#5 VillageGreenDeere OFFLINE  

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Posted October 30, 2014 - 05:30 PM

what most commonly causes stuck floats and and needle?


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#6 VillageGreenDeere OFFLINE  

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Posted October 30, 2014 - 06:03 PM

thanks everyone.  I'm a total engine newbie.  This is fun though.  It feels good to get a grasp on how these things work.


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#7 propane1 ONLINE  

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Posted October 30, 2014 - 06:13 PM

Vent in gas tank filler cap may be plugged. Won't let air into tank so gas can flow out. Just a thought. Could be some of the problem before you took it apart. Noel
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#8 crittersf1 OFFLINE  

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Posted October 31, 2014 - 06:04 AM

Needle is stuck


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#9 boyscout862 OFFLINE  

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Posted October 31, 2014 - 06:47 AM

If the fuel pump is pushing plenty of gas, disconnect the fuel line at the carb and test again. It may be the fuel line has swelled and won't let the gas through. If the gas flows well through the line then it most likely is a sticking float and valve or crap in the inlet passage of the carb. If it is the float and valve, you will probably save time in the long run by rebuilding the carb. Get a rebuilding kit for it.

 

Troubleshooting mechanical problems is an art and a science. Most good engine manuals will include a troubleshooting guide. I think that the best guides were in 1960s and earlier Chilton's and Motors automotive manuals. They can help you to understand what is going on. Good Luck, Rick


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#10 glgrumpy ONLINE  

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Posted October 31, 2014 - 11:21 AM

Plastic floats swell and catch on sides on onans.  they have replacement metal/brass floats that don't catch. Sometimes old hoses break apart on inside and chunks of the rubber get into ports and holes. I would replace old hoses from pump to carb. The little spring that holds needle onto float tabs might be mis-aligned and hanging it up? Not too common. Set the float level?? Get a manual to help you through some of these problems.


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#11 VillageGreenDeere OFFLINE  

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Posted October 31, 2014 - 07:53 PM

Ready, here is how much of a newbie I am.  I had things flipped around my mind.  For some reason I thought the floats job was to push down on the needle and allow fuel in for combustion.  So I paid no attention to the fact that the needle is designed clip into the float and then RAISEhe needle when the fuel level in the bowl drops.  Your all ready saying, "really kid".  So I clipped the needle in a perfecto!  A strong running Onan with such a nice idling sound!

 

It's amazing I pulled the engine, pulled all the tin and wiring, cleaned it, replaced the cracked oil pan and then cleaned the carb and didn't mess up anything until that point.

 

Tomorrow we haul fire wood up from the lower lot.


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#12 KennyP ONLINE  

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Posted November 01, 2014 - 06:25 AM

Glad you figured it out!



#13 HDWildBill OFFLINE  

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Posted November 01, 2014 - 09:22 AM

That's how you learn.  Now you know how the float works.






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