I have replaced all five glow plugs in my 1979 300D. After installing them and hooking everything up the way I thought it was when I took it apart, I attempted a start.
First of all, the glow plug light stayed on for at least a full minute, maybe longer--much longer than normal. When it finally went out, it FADED out, instead of just going out as normal. So when the engine failed to start, I glowed again and this time took a look under the hood, and the serial wires connecting the plugs were GLOWING RED! I have not seen this before, and assume that it is not normal.
I am at a disadvantage, because I do not have my MB Maintenance Manual CD with me, and am winging this job, with the help of people her, of course, but I believe I must have hooked something up wrong.
Any insights will be gratefully appreciated.