OK, so it’s a 1984 Kubota 3750 4WD diesel, not highway-ready (top speed is 14 MPH, and it’s pretty scary at that speed) - but otherwise it’s just another motor vehicle with a problem that’s driving me nuts:
When I try to start it, six times out of seven I can hear the starting solenoid go “clunk” but the starter never kicks in; except sometimes it starts cranking immediately, but most of the time if I turn the key several times in a row, at some point the starter will spin and the tractor will start up. (And sometimes - usually when I’m out in the back field - I can tun the key 20 times in a row with no luck; but if I wait 10 minutes and try again it it will usually start right up.)
I opened up the solenoid and found the contacts badly pitted, so I put in a new starter - no change.
If I put the battery charger on it for an hour, it would usually start up right away (but not always); if I didn’t charge it up then it would mostly go clunk. So I put in a new battery, checked all of the cables and put a new terminal on the main power cable (the old one was so deformed it couldn’t be tightened up) - no change.
I checked the alternator output, and it looks fine - getting close to 15V at the battery when the engine’s at working speed.
Could this be the ignition switch itself that’s bad? I can hear the solenoid kick in every time I turn the key, but maybe it’s just not pulling in all the way?