MSD plus Crane optical problems
 

I am trying to install a Crane optical trigger with an MSD-6200 and an MSD vibration-balster coil on a 72 porsche 911t. When the optical trigger activates (i.e when I am trying to adjust the coder timing), there is an arch between the + terminal of the coil and the center of the coil housing. The engine will start but runs terribly. Anyone else have this problem? Is this a problem with the coil? The coil had run fine with the standard ignition prior to installing the MSD unit.

Have you confirmed that you have it wired exactly per the MSD drawing? I've got a very similar set-up in my car and detailed the wiring that I used in this thread. Others have figured out how to make it work without the tach adaptor and you can find their tricks by doing a search on "MSD". My set-up has worked flawlessly and I just happened to have documented it for reference.

Thanks John,
yes, I first wired things exactly as described in the Crane documentation for use with the MSD. Then I tried to wire things as you indicated in your drawing. My Bosch CD box is taken out, so I connected the red from the MSD to chassis ground with the ballast resistor. When I do this, the fuel pump runs as if I had the key on. I didn't put the diode in since I thought this was to solve run-on.

OK, let me be a bit more specific. I connected the MSD box and tach adapter as described in Wayne's 101 book: heavy red to starter moter, heavy black to ground, tach adapter purple to original black/pruple from distributer, MSD thin white to Crane thin white. MSD orange to + at coil and MSD black to - at coil. Disconnected the connector from the bottom of the Bosch CD box and tied the MSD thin red, the tach adapter thin red, and Crane thin red, to the ignition red that used to be connected to the bottom of the CD unit. Then, when I tried to adjust the Crane sensor position at the distributor, instead of the diagnostic LED going on, I would see (and hear) a spark between the + terminal of the coil and the nose of the coil that houses the hi voltage out. Then tried to put in the ballast resistor between the three tied reds (MSD, tach and Crane) and ground but got the same result.

John,
do I leave the tach and Crane reds to the ignition red (that used to go the the CD) then have only the MSD thin red to the fuse red via the ballast resistor? Did your drawing show the diode between the MSD white and the Crane white?

Did this get solved? I am curious.

Yes, all works great now.
First roadblock was the arcing from the nose of the coil to the to the + and - terminals when adjusting the Crane optical trigger. This was happening since there was nowhere for the coil discharge to go (since the distributer cap was off). This went away once the distributer was put back together. Also, there was never any 'diagnostic LED' indication during the trigger adjustment like mentioned in the Crane instructions. So I just used the coil arc as the indication I was had the trigger set at the correct position.
Second roadblock was the ballast resistor. Connected one as John indicated in this thread referenced above (didn't need the diode however).
Started up easily and runs great. Didn't need the tach adapter either.
Thanks for asking.

i am new to this board. had a quick question. i have a 76 911s and i was changing the coil on it with one from from msd. after i replaced it i saw arching from near the + and _ terminals of the coil, then nothing. i have no power to the + terminal. all fuses are good. power going to the ignition box from the distributer seems fine but nothing coming out to the + terminal. did i fry the ignition box or cd box. and if so, by installing msd ignition system will it bypass the cd box.

I'm no expert on this, but suggest you try the MSD site. There is a discussion forum that I used to help problem solve and I recall there were a number of posts on the arcing coil issue. Good Luck