This works for me. When in doubt, pull the spark plug. If it's wet,
you've pumped in too much fuel. Spin it over a few times with the plug
out and the throttle open to blow some dry air thru it. Best to leave
it sit for a spell like overnight.
If it's not wet, take a real good look, make sure it's not wet. Put the
plug back in carefully with fingers, so you don't cross-thread it.
Tighten it just snug with a wrench, you don't have to torque it to 100
lbs. Now make sure the fuel tank is full. One new mower I had wouldn't
prime on a 1/2 tank. Give the primer bulb 5 good squirts. Pull the cord
gently to bring the piston up on compression. Then give it a super
strong pull with the throttle open. Repeat 2 times, then if it doesn't
start, go get a beer out of the fridge. Try again later.

JohnK