O. K. The disadvantage to a single wire alternator is they need a good amount of RPM to start charging. With that being said high idle no load on your little diesel is 1750 RPM. so what size pulley are you running? Next thing, I hope your wire is at least 10 gauge for safety purposes. Me, I would not use a single wire alternator. I would get a Delco out of a junk yard, have them check it and hook it up, You will need an oil pressure switch to activate it and disconnect it once the engine is shut off. Now what was the problem with your 12 volt generator. What do you intend to use the tractor for.