I have a old ford diesel genset that runs an air compressor . It fires up first go in the morning when its cold I let it run for 5 -10minutes then turn it off and try to restart it and it wont even crank / turnover . only thing you can hear is the diesel solenoid click once and then the starter solenoid once you turn the key to the start position . I will let it sit for 40min to 1hour and it will fire straight up first go Its a 12v system and ive bench tested the starter . it works perfect the battery is perfect , the connections are fine It starts when its cold all the time , seems kind of pointless testing the rest of the starting system because it does start? the starter DOESNT make and funny noises, start chattering or make any whine noises once the engine is hot /warm once its warm it wont even crank and its just dead silent only thing i did notice is the starter feels abit hot once the engine has been running for a few minutes , would this affect it and cause it to just not even turn over ??
Check your voltage while its hot and trying to crank either a warm solenoid that isn't working properly or a weak starter If you dont have full battery voltage at the starter work backwards till you find the problem If the exhaust is close a little heat shield may just help too
How long has it been doing this? I've never noticed a starter get hot, but then I guess I've never felt them after the engine has been running either. If the starter solenoid is clicking, then use a test lead with aligator clip to check the starter side of the solenoid, if that gets full battery voltage while you hold it to start, then the starter is not making contact when hot. Take it apart or take it to a shop and let the experts look it over.