Glow Plug Relay???!!!???
 

I've recently bought a 1981 mercede 207D which has stumped me with a glow plug problem. The engine will start after cranking for a while but idles very rough until it warms up, and when the engine is warm it'll start first crank no problem, these symptoms combined with the fact that the glow plug light is not coming on lead me to believe that I have a glow plug problem ( GENIUS!! ). I was hoping of course that it was going to be a simple matter of changing the glow plugs, no such luck!, I've removed and checked all the glowplugs, all are showing a 0.6 ohm resistance value. While I was doing that I found that there was no voltage getting to the plugs? I have tried in vain to find a fuse, I traced the wire back and found an unusual looking yoke on the firewall which I presume is some sort of a cut off switch, consiting of a heat coil with a bi-metallic strip switch in the centre I checked the continuaty of that and it's fine, there is also no voltage present. The wires thengoes through the firewall and behind the dash, and as far as I can see goes to the starter switch.
So where's the fuse? or am I overlooking something obvious here? what I could really do with is a wiring diagram, which I can't find anywhere. Would much appreciate it if somebody could point me in the right direction or offer some advice . :confused:

im not sure exactly what a 207D is. but i can through my opinion at you. I had a simular problem with both my 240D and 300D, turns out the glow plug relay needed to be replaced, Additionally, while i was at it, i also replaced the glow plugs just to be extra sure.

i had intermittent (very frustrating) gp relay failure and finally replaced the old serial system with a new duraterm relay w/pencil plugs. there's a recent thread about it...

There's a metal "strip" fuse in the relay, seen when you open the relay lid. Very common trouble source, both intermittant and total failure mode. Just replace it if ANY question about it.

You're probably right about the fuse in the relay, BUT! where's the relay? I seriously can't find it! I've tried tracing the wire back from the plugs as best I can without taking the whole dash off, and as far as I can see the wire goes to the starter switch, no sign of the relay! anybody got an idea where to look?

for anybody who's wondering what a 207D is, here's a pic.Attachment 43290

it sounds like you have the old style GP wiring, that block on the firewall should be the fuseholder. pop off the cover and see if there is a fuse like pictured above between two Phillips screws.
Cool Ride!!
John

Thought that myself but there's no power getting to thing on the firewall( it's some form of thermo switch thingy ) and there's continouity through the thingy, so I ruled that out.
It may be a bit of a beast to look at but I can have a shower and cook a steak in it! Try doin' that in a Camaro ! :P
Anyway I got my Golf GTI to smoke them Camaro's at the lights!!