I'm having problems too. I just checked the glow plug system this am and found that they all have good resistance, the relay seems to be working fine and shows 12v at the pins on the relay, but I'm only getting about 9v at the plugs themselves. I do also notice that the glow plug strip fuse gets quite hot, with even a tad of smoke, and it did also melt last year, when I scavenged one off my 80 300SD and put that in. It worked for a long time, until recently, when it no longer will start.

I don't know if it's due to issues with the glow plugs, though. Maybe it's a fuel related issue. But wanted to see if there are any thoughts on my 9v issue.

Thanks

__________________
1980 300SD (daily driver), 1981 300D (Inca Red)