I agree, it sounds like this motor is toast. Try this when its cold. Rotate to crank to TDC and see how fast the air gets by the seal between the sleave and the piston and try to get a feel for how much resistance there is. When these engines are new, its barely possible to turn the engine over because this seal is so tight. When an engine is on its last legs, there is almost no resistance moving from BTC to TDC. Also, find someone with a temp gun and take the temp at the glowplug sometime after 6 or 7 minutes of running or right after it cuts out. I'm betting that the temp will be somewhere around 320 degress because of the ineficient cooling due to lack of compression and possibly an engine running too lean.