If you are pumping the throttle without cranking the engine you might as well get out of the plane and pat it on the tail before you get in, they do approximately the same thing...nothing. Pumping the throttle only has an effect when the engine is turning, the effect is the same as continuing to prime the engine as though it isn't getting enough fuel to begin with. In most cases it is completely pointless.

As others have said, prime it more and when in doubt preheat. As for moving the throttle, put it in a half to an inch and just leave it. In my personal experience, people playing with the throttle seem to have all kind of starting problems. I personally do this and have only had one carb engine not start on me, due to bad spark plug in the #3 cylinder. Temps ranging from -25 to 80 F and all of these were horribly maintained 152s, 172s, and grobe gliders, one of the reasons I left that job.

These are the steps I follow, regardless of outside temp:

1) 2 primes, throttle in 1/2 inch and crank for about 10 seconds. If it doesn't sound like it catches stop and

2) 2 more primes, throttle to 3/4 inch and crank again for 10 sec. If it doesn't sound like it catches stop and

3) 2 more primes and throttle to an inch in, again 10 seconds of cranking.

If at any of these steps I hear it catch but fail to start I continue cranking past that catch point for about 5 seconds. This is to clear out whatever fuel was in there. Next I give it 3 shots of prime and repeat. If the same thing happens I give it 4. If it happens again this is where it gets a little tricky, I give it 4 shots then bring the primer out for the 5th shot but don't push it in. When I hear it catch I slowly feed in the 5th shot to keep it firing until it starts.


If all this doesn't work I assume it is flooded, but to be sure I give it 5-6 more shots to make it flooded. Then I push the throttle to about 2 inches in, almost half way and put the mixture at idle cutoff. I then crank the engine and do a start just like a fuel injected, shoving the mixture in when it fires. If it fails I return the mixture to idle cutoff and crank another 10 seconds to ensure all fuel is gone and go back to step one.

Hope that helps, good luck.