Small Engines (Lawn Mowers, etc.): Fuel overflow/flooding, briggs fuel leak

Question
I have a 10Kwt genset powered by a B&S 18HP Vanguard engine. Engine is about 10 years old but only has 200 hours on it. This has been in storage for over a year. The fuel system was drained and I ran the engine until it ran out of fuel. Recently I took it out of storage, charged the battery, fueled it up and it started right away. About 20 seconds into operation I noticed fuel overflowing the carb and shut down the engine immediately. After a few minutes I also noticed fuel leaking out of the exhaust. I turned off the fuel from the overhead 7 gallon tank and the leak eventually stopped. After a few minutes I reopened the fuel valve and in about 20 seconds the fuel started overflowing the carb and running out the exhaust again (Engine off!). I initially though the carb float might be stuck but after taking the top off the carb and checking it was found to be OK (in my opinion). Fuel is routed from the tank through a shut off valve to an inline filter,then a B&S 808656 fuel pump to the carb. I now suspect the pump might be the problem. Is there a simple way to check?  Any other ideas?  Thanks for your time.

Answer
You need to start by replacing the needle and seat.  Aside from a crack in the body of the carb, they're the only thing that prevents fuel from entering the carburetor.  Also hold the float under some soapy water and watch for bubbles and make sure there's no leaks.  You should go ahead and give the carb a good soaking in carb cleaner while you have it out and replace the gaskets.

You may need to polish the seating area of the needle, but I'd put it back together and try it before I did that.  Usually we'll do a pop-off test to check the sealing ability of the needle.  If you have a hand held vacuum gauge put about 5psi of vacuum to the fuel inlet and see if the needle will hold it for 20 seconds.  We do this before and after changing the needle, and seat if it has one that comes out.  If it won't hold after changing, then we'll polish the seat or the metal where the seat sits.

What we have nowadays is failures due to the ethanol blended fuels.  It deteriorates the rubbers, it leaves behind a lot more deposits and it absorbs water and leaves the mineral deposits behind.  It's just bad stuff all the wy around.  We recommend using SeaFoam in the fuel all the time.  Your method of storage was the right way, but unfortunately this ethanol fuel is going to cause problems sometimes no matter what you do.

Try this and let me know what you get.  Thanks, PK.