I would check to see if the float in the carburetor is stuck open.
If you write down the model number, you can type it in on Briggs' website and download the service manual which will have exploded views and breakdowns of everything.I'll see if I can find any info on how to check the float for sticking,,, Carbs are not my specialty... I do valve adjustments, some electrical and normal maintenance... Any hints would be appreciated... Tom