Installed a spark tester between the spark plug and ignition coil. After priming the the carburetor with gas and attempting to start while pulling on recoil cord, the engine will fire and smoke will come out of the exhaust. At that point the spark cuts off as indicated by the spark tester and the engine will not start. I removed the black wire from the ignition coil, but it still will not start. I'm not aware of any other kill switches on this model. What could be the issue?