This has happened 2x: After running the Disco a long distance (30 miles or more) it will fail to start after shutting off. I did try my battery booster but that fails to start it. Turning the key does not start it, there is no sound of clicking, engine fails to turn over. So, letting it sit for about 20 min it will start. Any ideas? Thanks

 

Check your Crank Position Sensor.
It the truck starts after a cool down it could be that sensor.