Why does my briggs & stratton engine start and then stops immediatley?

Most likely the float has stuck. Dislodge it or replace it.
To check the float, take the air filter off and then cover it 3/4 of the way with your hand, while some one cranks it after you have primed the carb. If it stays running, then its the float.

John Mark
August 2008

You either have water in your gas or a dirty carburetor or both. In any case, take your carb apart, being careful to not lose any parts, clean it, and reassemble it. That should do the trick.

Bud Dacres
May 2007

you could have blocked up carbeurettors.
if you filled all 3 lawnmowers up with the same petrol can, and there was some dirt in the petrol, it could have blocked up the jets.
Remove the carbeurettor, then unscrew the idle jet(if you have one) making note of how many turns it took to remove the jet, do the same for the main jet, and soak the carbeurettor in petrol. shake it out and spray down the holes where the jets were with an air compressor, put the jets back and put the float chamber back on, then put the carbeurettor back on and fingers crossed it should run.
it might take a bit more pulling on the chord to get the mower to run as you will have to pump the fuel through the carbeurettor.
if this doesnt work, try cleaning out the air filter

Stephan
May 2007