Dave, the ignition should never be fired without the plug installed. If your ignition has one of those metal caps on it, you can push the plug into it and check the firing with the plug out of the engine. If your ignition has a rubber boot for the plug and a ground wire you can do the same thing with the ground wire clamped to a metal part of the spark plug. In either case you do not have to have the plug in the engine. You can turn the engine over by hand. Dan.