I have a '80 300D, 155k miles. I had noticed recently that on occasion she would lose power when cold, and was idling roughly. I did not drive her for a while, and when I did there was some smoke, black, which is unusual for this car. As I was driving, at idle she began to die. I coasted to the side and now she will not restart. It appears that there is air being sucked into the fuel system. Is there an area where this is most likely?