My car was running just fine until I stopped for a cup of coffee. When I returned to the car it wouldn't start and hasn't run since. The mechanic said it needed a new motor. I don't see how that could be when it was running fine. He said there was no compression at all. Recently I was talking to a man that said he was a diesel mechanic. He said it might be the timing gear or chain because quite often old diesels kick back when they stop turning and that can cause a worn chain to skip. My question is would this cause the engine to have no compression at all? Thanks to anyone who might help me. Doc