JD 4020 won't start when hot

However, I'll tell you what we did to ours. Ours turned over very slowly when the engine was hot. I noticed the starter was also hot. So hot that you could barely lay your hand on it. The starter was picking up heat from the engine. It always acted up on a hot summer day. We learned not to shut the tractor off on a hot day unless it was headed down hill.

One day I was looking at a high performance car catalogue and I saw heat shield blankets. They are made to wrap around the starter and reflect heat. I ordered one and I haven't had trouble with the starter since.

Your problem may be totally different than mine, but if your starter is turning slow only when the engine is hot, lay your hand on it the next time the engine is hot and before you try to crank it. If you crank on the starter for a while, it will be hot anyway from the workout. Starters are mainly made of copper which is a good conductor until it gets hot. Heat causes a lot of resistence and restricts current.

Anyway, hope this helps. Good luck!

If you have a diesel, the most common reasons for poor starting when hot are:

1. Slow cranking due to poor batteries, improper charging voltage, corroded connections, or starter in need of repair.

2. The "HEAD AND ROTOR" your injection pump may be worn or scored. These are replaced as a matched set by a diesel injection shop. (NOT CHEAP!)