It has always been my impression that there are 2 types of primers for
small gasoline engines:
1) One type primes the combustion chamber by squirting raw gasoline
into the fuel intake.
2) The second type primes the carb by pumping gasoline into the fuel bowl.
One crude method of determining the type of primer is by observing the
priming instructions. If you are priming the combustion chamber, then
you'll be instructed to pump the primer just a few times. If you are
priming the carb fuel bowl, then you are probably instructed to pump
A better method is to test the primer while the engine is running. Have
another person rapidly pump the primer while the engine is running. Ten
very rapid pumps should work fine. If the engine operation is not changed
with all of that priming, then the primer delivers gas to the fuel bowl
and not to the combustion chamber. But if the engine sputters or stalls,
then the primer is delivering fuel to the combustion chamber and the rapid
primer while running is flooding the engine with too much gasoline. Often
this will cause the engine to sputter and stall.
I've never read any of this anywhere and it is just what I've picked up
over the years. I have small gasoline engines which display both sets
of behaviors, so I'm a believer that there are 2 priming methods.