Need Help with Glow Plug retrofit on '76 300D "W115"

[samdon]

I bought this kit from Russell at Deisel Giant. It included five pencil style glow plugs, connecting wires, and a bar fuse. Being that this is a w115 chassis 300D, a number of things are different than the much more common w123 chassis 300D. Most notable is the grounding method. The 115 cars do not have the braided strap grounding the series. The sensor that is threaded into the block has, of course, the sensor wire plugged into it that I assume terminates at the relay under the steering column. It also has a thicker black wire that was originnaly attached to the front-most glow plug. I guess that this was the original ground for the system.

The problem I have is this. The plugs get no voltage when the key is turned to the run position. If I jump the 5 and 6 pin at the relay, they get hot immediately. Russell has told me that the thick black wire at the sensor needs to see 12V in order for the system to function. I tried this once and got a fireworks show. I fused the jumper wire so no damage was done but obviously this is not correct. Russell has not worked with the W115 300D so he does not know for sure what to do.

I know this has been done before and I've searched until my eyes hurt but the exact answer still eludes me. I could just wire a switch at the relay plug between 5 and 6 but I want a more elegant solution......I want it done right.

Can some wise soul point me in the right direction? I need this thing buttoned up very quickly.

Thanks,

Sam