was it new or used?

also will it start again after the thing cools down completely?

If used, and restarts when cooled and runs for 5-10 mins prolly the pinch is bad. I've had this many times when I bought used Nitro RC's... if this is the case easier, and cheaper to replace the engine with a brand new one
If you take the glowplug out and turn the flywheel by hand there should be resistance when the piston hits the bottom of the shaft. If there is none more then likely it needs a piston/sleeve, but like I said usually its cheaper, and easier to get a new engine.