Need guidance and leadership -

I've finally gotten the D-Jetronic on my 2.0 working again... BUT, when I connect the Black/Purple wire to the coil, it nearly kills the engine.

Question is:

Can I infer that the wire is bad (worn through somewhere)?
Or,
Does your experience indicate that the tachometer is failing?

Has anybody else experienced this before?

Is there some way to test?

Thanks in advance.

Is the wire insulation on the black/purple wire melted?

No, other than a little dirt, it looks fine.

I am inclined to isolate the wire and check continuity from the coil to the relay board... and if that checks out, then do the same from the relay board to the tachometer.

What are your thoughts?

I don't believe (from looking at the wiring schematics) there are any other junctions, are there?

thanks in advance.

or are you thinking that maybe I am having a high voltage leak to the ground terminal?

The engine runs fine when I pull the black/purple wire off.

Isolate it. Remove the wire on the tachometers middle terminal (should be a black with purple stripe wire). Reconnect the black and purple wire at the negative terminal of the ignition coil. Start the car, if it remains running, the tach is faulty. If the car fails to run, you have a short in the wire

You're on the right track with isolating the wire in the middle first. Check continuity of each portion, end to end and to ground.

Its common to incorrectly connect the black/purple to the coil+ and the black/red to the coil- which melts the black/purple inside the harness. If so it could be shorting internally against any other wire in the harness. It should not have continuity with any other wire in the harness, if it does...the harness needs to be replaced.

I had a similar issue with the tach wire. It turns out it was some type of short in the wire bundle over the engine. Disconnect the wire and the engine would run. I ran a new wire from the distributor to the relay board. All is well now.

Thanks to all!!!

I'm all over it... and shall return from the abyss, to file a complete report this weekend.

Cheers!

ok, its running great!

don't know exactly what was happening but, the ignition wires were some crappy off-brand. Replaced them with the Bosch real deal. Voila! the tach works!

I can only surmise that there must have been some low - level arcing just to the black/purple wire but not the green... HUH?

Anyway, while I was at it, I installed 4, 019 injectors and the engine is running better than ever!

Thanks to all for the guidance and leadership!

Now onto the brakes!