Ignition Wiring Question (MSD related)

[vntgspd]

Okay, I've read a ton of threads from my searches but haven't seen clarification on this particular issue yet:

My new MSD install in my '69 911 has no spark.

The MSD troubleshooting guide did not yield any positive results.

I spoke with MSD tech who told me to disconnect the tach adapter and then try it (so then what if it does work without the adapter! )

He also said the large power and ground leads MUST go to the battery which I am not doing (and don't feel is necessary).

I am getting my constant battery voltage from the large lead at the rear of the engine compartment electrical panel. This lead goes to the the same starter lug as the battery cable. This panel connection is also where the large red wire from the alternator goes.

I am getting ground from the lug on the inner fender near the engine compartment electrical panel.

So, does it matter if I get power from the electrical panel or the starter lug since they are all connected in sequence anyway?

Do I need to get ground from the lug at the rear floorpan where the engine ground strap is located?

Any opinions are welcome!

Thanks,

David

[Jim_Brown]

David-

On my '69T I have the MSD connected as you describe and it works fine.

Where are you getting your switched 12V? I used the fuel pump circuit.

Have you checked to make sure the MSD unit is getting the trigger signal?

IIRC - Put the distributor end of the coil lead near a grounded piece of metal and with the ignition on, ground and remove the MSD trigger signal wire a few times. You should get a spark from the coil wire to ground every time you pull the trigger wire away from the ground.

Good Luck,
Jim

[vntgspd]

My switched 12 volts is coming from the same wire that the Perma-tune was connected to (red/black maybe?). I have a Pertronix ignitor and that also connects to the switched 12 volt source.

When I reconnected the Permatune using some quick wire splicing (and disconnecting the MSD) the car fired up. So, the signal from the Pertronix is working and getting to the buss bar where the MSD also connects. The 12 volt switched source would also seem to be correct.

[Beetle Bailey]

When I installed my MSD unit I had to run an additional ground from frame to block to get a good ground. My car had sat a while so my ground issues were pretty evident. I also had read on another post here that someones elses MSD unit wouldn't work without the rev limit pill inserted. Mine runs with or without but that might be something else to look at.

[Eagledriver]

Do the test with the points lead as described above. Measure the 12 volts at both the switched and unswitched power leads. If you don't get a spark when you unground the white wire (point's wire) then your MSD box is bad. Your connections sound fine as far as not going directly to the battery. As you say the wires you are connecting to at the engine go to the battery and alternator anyway.

-Andy

[vntgspd]

Thanks for the input. I checked every wire for necessary voltage, continuity, correct routing, etc. I'm pretty confident the box is bad.

I just put the Permatune back in and it's working well. I'll send the MSD out for repair as I do believe that it will improve idle quality by keeping the plugs clean.