I have a 1987 300D Turbo and was unable to start it this morning. The temperature is 0 F. In the past, I did not have any trouble starting the car in -10F weather. This morning, the glow plug light did not light when I turned the key to the right. I just heard a clicking coming from the dash. I could not even start the car when I pulled into heated, indoor parking and received a jump start. Does this sound like a glow plug problem or is this a problem with the Preglow Time Relay?