Carburetor keeps flooding 1 minute after starting

johncini7September 19, 2012

I have a Briggs and Stratton 18.5 hp engine. The carburetor needed cleaning because it wasn't getting enough gas through one of the jets. I had to pull the choke out half way or it would keep surging. After I cleaned the carb and put it back together, I started it and within one minute it died because of the over flowing gas from the top of the carb holes. I thought it was a problem with the need valve cause the gas was over flowing. I went and bought a new needle valve and put it in and the same problem occurs. I checked the float for holes and it is ok. I thought some dirt might have got in the seat so I blew the entire carb out. Every orfice. Same problem. I went back to the parts department and they pressure tested the seat with the new needle valve. They told me the seat was bad. I thought that was strange since the problem only started occuring after I disassembled the carb. I bought a new upper half of the carb. I put it on and it still floods. Somehow I keep thinking that the needle valve is not stopping the gas flow. I have rebuilt many carbs and never had a problem before.

Any suggestions?

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Without the model and type numbers from the engine itself there is no way (for us) to determine what carb is being discussed.
Given the info you have posted leads me to suspect that the float is operating at a high level than specified and thus is never actually seating the needle valve.
Post the actual Briggs Model Number and Type Number from the engine itself.

    Bookmark   September 19, 2012 at 10:34AM
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The model number of the Briggs and Stratton motor is 461777 and the type is 0137EI.

The carb part number is 693479 (4 screw fuel pump mount)

    Bookmark   September 19, 2012 at 12:58PM
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I just bought and installed a fuel shut off valve.
After I installed the shut off valve ( 6 inches from the gas tank) I started the engine and closed the fuel valve almost all the way (leaving it open about 15 to 20%). Now no flooding. It must have something to do with the gravity pull of the fuel giving too much pressure which lets the gas continue into the carb overflowing through the small vent holes in the top of the carb. I read this in a post somewhere. They said if the tank is more than 2ft above the carb it will force feed the carb. My tank is only 6 inches above the carb. This is the way it was set up from the factory on this MTD Yardman Tractor when it was built in 1999. The engine runs now. I drove the tractor around my property and it never flooded. I still need to fix this problem. I know it is not the carb because I replaced the upper half of the carb with a new one. I had the same problem with the new "Seat" and new "needle valve".

Any ideas? The float is non adjustable.

    Bookmark   September 19, 2012 at 5:13PM
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Remove the float, stick it in a can of gasoline, and let it set until next day. You might find that the
'float doesn't! The float can develop a leak all by itself, and will drive ya to the poor house from buying everything except a new float!

    Bookmark   September 19, 2012 at 7:35PM
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Ok Rusty, sounds good. I will take the float out of the carb and stick it in a can of gasoline. Should I put a weight on the float so it is totally submerged into the gasoline? Let me know. I will do it. What ever you say.

    Bookmark   September 19, 2012 at 7:54PM
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Sure, you can weight the float. you could very well have a seat issue too. Here's the thing with the inlet valve. The wire that retains the valve to the float can sometimes bind on the tower that the float attaches to. So, position the wire so that it is furthest away from the tower. Know that the vent holes are open as well./

    Bookmark   September 19, 2012 at 11:54PM
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Also flush the fuel line.
When disassembling, you'll often break loose "chunks of crud" that were attached to the inside of the fuel line.
If it's deteriorated at all, replace the line.

    Bookmark   September 20, 2012 at 10:36AM
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To tomplum.......I don't believe I have a seat issue because I purchased a new upper halve of the carb which has the seat in it. I put a new need valve and installed it into the old lower half of the carb then I started the engine and I had the same promlem.........flooding through the carb top air vents after 1 minute of running.

My particular carb does not have a wire holding in the needle valve. It has a groove that slides into the float.

    Bookmark   September 20, 2012 at 8:22PM
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To Bill Kapaun........ I did flush the line real good. Twice. All the way from the tank to the carb. The fuel line is not cracked or rotted.

    Bookmark   September 20, 2012 at 8:24PM
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Ah yes, I see which carb you have now. Had you also installed a new pump kit?

    Bookmark   September 21, 2012 at 1:07AM
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To Tomplum No I took the pump apart and checked the gaskets and springs. Everything looked ok. I figured if the pump was bad it would be pumping not enough gas, Correct...................Not more gas!

Have you ever heard of a pump being defective by pumping too much gas? If so I will replace the entire pump with a new one.

    Bookmark   September 21, 2012 at 7:48AM
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Johncini7 I was searching for the same problem you have/had. Did you figure out what it was? I need to fix mine and it would be great to see what the problem was?


    Bookmark   October 29, 2013 at 8:18PM
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