I second having the battery checked, I just fixed a starting problem on my tractor and it turned out to be the battery. I was sure my battery was fine, since it had never showed any weakness up to that point and when I tested it with my multimeter it read 12.5V. I could not start it with my battery charger connected and on the 75Amp starting setting, but when I jumpered it with known good battery it started up fine. I was surprised that I was not able to start it with the battery charger, but apparently the 75amps was not enough to kick it over. BTW the charger light indicated that the battery was fully charged as well. I spent a lot of time looking else where for this gremlin before I came back to checking the battery.

1954 GMC 1/2-ton Longbed
1971 Pontiac LeMans Sport