I have a 1990 500sl with approx. 50,000 miles. The car runs really great . I went on a 5 hour drive, and parked it for almost 1 hour and when I tried to start it, the engine would not turn. There is ignition , but the engine will not turn. it has been at the dealer for 2 days now, and they tell me that there is no reason, that this car should not start, but it won't.any ideas guys. thank you.