I have almost 1600 hours on my TC45D and this same problem crops up from time-to-time. It's as if the starter or soleniod stick. I tap on my starter solenoid and it starts okay most of the time. Short of replacing the starter, I don't think I have a good solution. Some say that the stater circuit needs redesigned because there are times the relays/switch do not supply enough voltage to the solenoid. I can't say if this is true because I can't get mine to fail long enough to troubleshoot the problem. After a few retries or tapping the solenoid, mine normally fires right off. It only happens about once every 6 months and seems to happen more when the tractor has been running and is hot. I don't think I've ever had it happen when the tractor is cold.
Sorry I couldn't be more help. It's a frustrating problem and one shared by many of us with these and similar tractors.
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