Small Engines (Lawn Mowers, etc.): spark plug, excessive oil consumption, spark plug cable

Question
engine will not run unless i pull wire away from tip of plug.every year I have to replace plug.Why does this happen and what causes plug to do this?
                            thanks

Answer
There are a number of things that can cause a spark plug to foul.  Some of those being, excessive oil consumption, engine running too rich, and engine running too hot.  As for the running only when the plug wire is pulled away from the plug, you must have a hole through the insulation on the spark plug cable that is in just such a position that it grounds out when it is attached to the plug.