Hello all, I'm new here and this is my car:
http://i556.photobucket.com/albums/ss9/RetroHomeSlice/Mercedes%20w123%20200d/DSCF9106.jpg

A 1979 200D - same engine as a 240D, but a shorter stroke. The 200D wasn't sold in the US, presumably because it's too slow. It shouldn't have been sold in Europe either; this thing is glacial!

Anyway. When I bought the car, it wouldn't start. I didn't have a lot of free time, so I sent it to a classic-friendly garage; they replaced the glow plugs and wiring. After that it started, albeit a little slowly (perhaps five seconds of cranking) on cooler days, but starting straight up on warm days. This morning, however, it wouldn't start. Glow plug light came on as usual. I looked under the bonnet and the live wire between 2-3 was glowing red hot! There'll be a voltage drop somewhere in the wiring so the first and second plugs aren't getting any juice. I can't test this at the moment because the plugs work on the old push-pull starter, and I don't have a glamorous assistant to hold the button out while I poke around with a multimeter (taking a live off of the battery could work, though).

Anyway. I took everything apart:


Cleaned everything up and put on the lower wires:


Then the upper wires:


Put it all back together, and it's still glowing. Originally the car had loop-type plugs with a single live wire in series. However, I can't seem to tell whether these new plugs are loop-type or pencil-type... and it also appears to be wired in parallel. I don't know why it has two (upper and lower) sets of wires either - I haven't seen that on any other car.

Can somebody shed some light on this, and advise me on how to put it back together properly? Figuring out whether the plugs are loop or pencil is the first step. I'd rather not have to remove them!