Is there any way to adjust the timer on the glow plug relay? I have tried 3 different used relays on my 83 300SD and the glow plug light does not stay on long enough to provide a smooth start. If I wait a few seconds after the glow plug light goes out, the engine will start and run without stumbling. Which means that the glow plugs stay on after the light goes out. Also, the glow plug light should stay based on the feedback from the engine coolant sensor, and this is not happening. The glow plug light goes out quickly regardless of the engine temperature.