If you have trouble starting on cold mornings, it may be your heaterplugs have failed. Disconnect all and try a continuity test to find faulty plug or plugs. Run the engine until cooling fan cuts in(hot) before trying to remove old plugs & use a hex socket if possible not bi hex. Unfortunately in many cases they are not easy to get at, a flexhead spanner(socket)is ideal. Now let the engine go cold before fitting new plugs & lubricate the threads. DO NOT overtighten!!!! Otherwise impossible to remove plugs will oft succumb to this trick,best tried first not last. Good luck. Skylarc.