# Fuel Overflowing Carb on Briggs Engine



## mikulskn (May 31, 2016)

I have a Simplicity rider with a Briggs & Stratton 17.5hp ELS500 engine, model 31L777 type 0036E1. When using the rider after a few minutes, the engine would sputter with a little smoke and then die. Upon taking the breather tube off the carburetor, there was fuel in there (and into the crankcase as well). So I had figured that the needle in the carb was not seating properly, so I replaced the needle and needle seat even though the old ones looked good. And even though the solenoid would not be responsible for fuel overflowing the carb since the needle/float should stop the fuel, I replaced the solenoid anyway. I also changed the oil and filter. 

Upon using the rider again, the same thing happened. After a few minutes of using the rider, it sputtered and died. And again, there was fuel in the breather tube connected to the carb. After taking it to the garage and shutting off the engine, I pulled the breather tube off the carb again, and fuel would leak out where the breather tube meets the carb. After turning the fuel shut-off valve off, the fuel would stop dripping out of this opening. And I could keep repeating it.

I took the bowl off, and I could stop the fuel by pushing up on the float with my finger.

I am puzzled how the fuel could keep flowing thru the carb when the needle and seat were replaced and the float looks great. The float seems to move without obstruction, so I do think the float is getting stuck.

Any ideas on what the problem could be???? Could it be related to the fuel pump? Can there be something causing the float to not shut off the fuel with the needle? I have read about a bowl “vent” problem, but I have never heard of such a problem or have any idea of what to look for on the carb.


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## AVB (Nov 28, 2014)

Which of the three carburetors do you have? Walbro, Nikki or Ruixing. I suspecting it is a Nikki but need to be sure for troubleshooting purposes.


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## mikulskn (May 31, 2016)

Thanks for responding....it is a Walbro. See attachments for your reference.


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## AVB (Nov 28, 2014)

Didn't pressed the seat in too far did you? Float must be level or slight above when the carburetor is inverted. Also make you use the correct seat as there is gravity fed and fuel pump fed versions. The instructions in the repair manual is incorrect in this reference.

You also can test the sealing while invert with a pressure pump. It shouldn't leak until at least 10 psi is applied.


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## mikulskn (May 31, 2016)

Thanks AVB for the reply. I think the seat is pushed in the correct distance since I took a picture before to compare. When inverted, it seems level....see attached pic. And when I remove the needle and then invert, the float goes down much further. BUT I did not know there was a difference in the seat depending on fuel pump or not. I did some checking and I found I am using the seat for the gravity fed setup, so I will have to get the correct seat for pump setup. Thanks for that insight.

I will do some googling to look up a way to measure the pressure with a home-made setup. But now I beginning to wonder why there is a fuel pump for my set up. I bought my rider used, and the owner told me the original engine was replaced with a different type engine. This one has a fuel pump even though the fuel tank is right behind the engine and a good amount higher than the carburetor. Maybe the original engine did not have a fuel pump. Could it be that there should really not be a need for a fuel pump in this situation? Can I just disconnect the fuel pump by making a line directly from the tank to the carb, and let it be gravity fed? Or will this not work? Is it a no-no to do it with this type of engine?


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## AVB (Nov 28, 2014)

Yes you can delete the fuel pump if the fuel tank is higher than the carburetor.

That fuel leak can partially explain now knowing you used a gravity flow seat as it take considerable more float pressure to stop the fuel pump pressure. But it should stop fuel leaks when only the gravity pressure from tank is applied. I had a few seats that leak even when new due a flaw or didn't seal around the outside seat and carburetor mount. This is where the pressure test help find where the leak is.


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## mikulskn (May 31, 2016)

I think will try connecting the fuel tank directly to the carb. I will use a fuel shut off valve for the hose the comes from the dipstick to the fuel pump....i think this would be the best way to dead-end that hose. I will get some hose and a shut off valve, and see when I can get doing this that because it is going to take some doing to get to the underside of the tank and the fuel pump. And in parallel, I will see if I can come up with my home-made pressure test...I am thinking to pressure it in the 5-10 lbs range, and see what happens.


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## mikulskn (May 31, 2016)

Tonight I disconnected the fuel pump and tied the fuel tank directly to the carb. I changed the oil. Then it started right up. I will not be able to try out the rider since I am headed out of town for a few days, but will update this later. I also have to buy or come up with a carb pressure tester, and I can do that next week or so since it is so easy to take off the carb. But I am hoping with the fuel pump removed, and with a needle seat that matches the gravity feed setup, that everything will be good from now on.


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## mikulskn (May 31, 2016)

I squeezed in cutting my lawn tonight. Used it 30 minutes. It ran fine now. After finishing, I took the breather tube off the carburetor and there was no fuel in it. So that is a good sign. So I think eliminating the fuel pump variable in this situation may have solved the problem. Thanks for the help!!


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