Small Engines (Lawn Mowers, etc.): Briggs and Stratton 4.75Q on Murray 22 Died abruptly died while mowing, briggs and stratton, starter rope

Question
I had been mowing for about 15 minutes when my Murray 22" mower with the Briggs and Stratton 4.75Q engine abruptly quit.....I thought it was too soon to be out of fuel as I had fueled The mower and cleaned the air filter before starting.  I added more fuel and pumped the primer (red rubber dome that you depress)about a dozen times,....the usual amout that it takes, pulled the starter rope and nothing.....primed some more and tried again...nothing....added some more gas (tank looked like it was half full) and pulled the rope start...and still nothing.  I decided I should try a bit of fuel in the carb which always works for the first start of the season....nothing....a bit of Starting ether sprayed in the carb which also always works...and nothing.

I figured this ruled out lack of fuel as the problem, so, I pulled out the spark plug and wire brushed it (it was a perfect beige-brown color when I pulled it) and re-inserted and tried again.....nothing........decided I would try a new plug before assuming that the problem was in the ignition system itself.   Installed a new plug......primed a little and tried, nothing,...primed a lot and tried.....nothing.....

Im now thinking that the spark is not either being generated or its not making its way to the spark plug for some reason.

I old and new Car ignition systems,...but dont understand mower ignitions....guessing they must be some form of a magneto system where the spinning magnets past a fixed winding somewhere are creating voltage which is stepped up by another winding/transformer.

Any suggestions where to look or how to diagnose this guy?

Brian in Austin

Answer
hi brian

sounds like  briggs  side valve with pulsa prime carb   model 10G902
can you feel good compression ,  try spinning the engine backwards  , with the plug out and your finger over the plug hole it should rebound abruptly if so  assume compression  ok , but not always definative ?

try new plug

is there a spark ?-  pull ground wire at the kill switch connection  recheck for spark
if no spark   aramature has quit

if there is spark  & is a happening at the right time
check for shawen / bent flywheel key   

has the engine got a the correct amount of oil  and correct type

is the ground wire  going to coil  grounding some where ? possibly at the switch or along where the wire is routed

could be a valve stuck open  if no compression

sounds like primer is working if see a shot of fuel been squirted into carb throat,

have a look and let me know what you find

cheers  paul