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Garden Tractors Discussion Forum

Briggs Stratton 18.5 I/C Flooding Issue

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08-05-2014 17:19:16

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I am working on a 18.5hp I/C Briggs engine That will start and run for about a minute then floods out then shuts down. Already rebuilt carb but kit (PT#693503) didn"t come with replacement seat. Does this engine (42a70-2238-e1)have a replacement seat or do I have another problem (to much fuel pressure)?

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08-06-2014 19:26:24

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 Re: Briggs Stratton 18.5 I/C Flooding Issue in reply to kdagenais, 08-05-2014 17:19:16  
If that is the engine/carburetor I think it is:

check your float.

If the float is not full of gas, check the body for a crack. Fill the carb. bowl with gas and see if it runs through to the venturi.

All the gas is supposed to go up into the top and then feed back down another passage to the main jet.

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joe csuti

08-06-2014 02:51:46

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 Re: Briggs Stratton 18.5 I/C Flooding Issue in reply to kdagenais, 08-05-2014 17:19:16  
Check date code on eng,briggs manual states eng after date code 98101500 inlet seat not replaceable in carb,another possible cause of problem could be fuel pump diapham bad/leaking dumping gas into venturi of carb/intake manifold,pump is mounted on carb but is treated as a seperate item & requires a seperate rebuild kit to service.

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08-05-2014 20:48:38

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 Re: Briggs Stratton 18.5 I/C Flooding Issue in reply to kdagenais, 08-05-2014 17:19:16  
I have the same engine in my rider - it's a flathead twin, right?
I ordered a carb kit from partstree (it was $27) and it included the pump pieces and the carb pieces - needle and seat included. It had several gaskets for the top half of the bowl so it covers many different units.

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08-06-2014 04:00:20

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 Re: Briggs Stratton 18.5 I/C Flooding Issue in reply to Notjustair, 08-05-2014 20:48:38  
I rebuilt the fuel pump as well parts came in kit and engine is after date (9901075) mentioned above. Which answers question for seat. Still got to believe there is a valve of some sort on the pulse line so it doesn't push instead of creating vacuum.

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joe csuti

08-06-2014 13:58:26

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 Re: Briggs Stratton 18.5 I/C Flooding Issue in reply to kdagenais, 08-06-2014 04:00:20  
Went back & took a slower look at carb assembly in manual,one thing I did was mistake pulse nipple for a fuel line,while my manual gives no info on rebuilding pump,but looking at pics of parts in rebuild kit pump diaphram appears to be similar to design of diaphram used in pulse jet carb used on smaller hp eng which has a spring/cap on one side of diaphram,in smaller carbs of this design it's possible to install spring/cap on wrong side of diaphram which will allow diaphram to leak & flood eng & possibly damage diaphram,while I have never personally rebuilt this style pump on carb you have maybe one of the other guys can tell you which side of diaphram spring/cap go on unless there were instructions furnished with rebuild kit.

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08-05-2014 20:25:49

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 Re: Briggs Stratton 18.5 I/C Flooding Issue in reply to kdagenais, 08-05-2014 17:19:16  
There is a way to correct a too much pressure problem. It is somewhat easy to try for a temporary solution before making it permanent. In the fuel line between the pump and carb, install a y connector. Route one line to the carb and put a restrictor in the other line. Something with about .040 size. Route this to a catch can to see if it works. If it does then route it back to the fuel tank for a more perm solution. A Hobart wire feed tip would work fine for the restrictor. They come in various sizes. This is refered to as a "pill" in racing engines. We use them all the time on our racing go-kart engines.

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08-05-2014 18:28:12

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 Re: Briggs Stratton 18.5 I/C Flooding Issue in reply to kdagenais, 08-05-2014 17:19:16  
What fuel pump are you using? If it's the crankcase pulse diaphragm pump, no, it can't make too much pressure.

If you're using an electric pump, yes, it probably is too much. Those carbs are only designed for a few ounces of pressure.

Could be something is up with the float, level adjustment, or trash in the fuel.

Not sure about the seat... If it comes out I would assume it is replaceable.

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08-05-2014 18:34:57

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 Re: Briggs Stratton 18.5 I/C Flooding Issue in reply to Steve@Advance, 08-05-2014 18:28:12  
Doesn't show a seat in parts diagram and I am using the pulse pump. Since there is no listing in diagram leads me to believe have to change upper half of carb for seat. After poking around on internet seems this is common problem and no answers. Even found someone that replaced the top half of carb (seat included) and still has issues. Wondering if there is a check valve on the pulse line that is bad.

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