Trouble shooting
If you are having a problem with your ignition there is a couple ways to help you track it down.
First if the engine is mounted to a plane and you are having a problem, Bypass all switches and electronic devices and hook a battery direct to the ignition.
If there is still a problem, install a plug into the plug cap, Hook up a good battery to the ignition and unplug the black connector going to the hall sensor, Take a small wire and touch the two outside wires on the connector, The ignition should fire each time you touch and then release the wire from the connector.
If the engine has crashed or nosed over and the spark plug hit the ground you could have damaged the plug cap or cracked the porcelain on the spark plug, Just because it will fire outside the engine does not mean it will fire under the pressure of the engine.