Here's the problem I've een having although I am not sure it is that same as yours...it usually occurs after i shut the car down when getting diesel or at the store. When I get back to the car I stick the key in, turn it, the glow plug light comes on and goes out, as expected, then I turn the key to start the car. All that happens is that the car turns over and over then I go through the cycle again. After a couple tries it finally starts.

I suspect that it is due to a bad ignition switch since I also have issues with my HVAC not coming on occasionally (I have to turn the key back slightly while the engine is running until I hear the solenoids (or something) 'click' in the dash then the HVAC works). Basically I think the problem I am having is due to a worn out tumbler/ignition switch. Perhaps you as well?

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85 300TD Turbodiesel 299,376 miles