MSD6A and 8920 Adaptor wiring Diagram

[dschloe]

I was looking for a wiring diagram for the MSD 6a and 8920 adaptor for a Porsche. Or help with the instillation. I'm working on a 77 911 with an 80 3.0. I have the car running great with the MSD unit but can't get the tach working.
Here's how I have it connected.
From the MSD to the CDI plug
violet to the black wire on the CDI plug
Green to the Green on the CDI plug
Thin red to the red 12 volt power on the CDI plug
Orange to + on the coil
Thin Black to the - coil
Thick red to positive on the starter
Thick Black to the ground lug.
Car runs great but I'm confused when it comes to the tach adaptor can someone help please. Directions say red to the 12v power
Black ground
White tach signal
Violet to the tach wire.
I hook all this up but tach does nothing now. When I first hooked it up the tach fluttered a little worked when I pushed the throttle then started acting sporadic then quite.
Thank you for any help

[mreid]

Is the tach wire connected to the tach lug on the MSD box?

[timmy2]

Interesting, I just looked at the MSD instructions and they call for a 8910 adapter if using the white trigger wire.
http://www.msdignition.com/uploadedFiles/MSDIgnitioncom/Products/Ignitions/6420_instructions.pdf

I'm confused by your wiring installation though, your '80 distributor should be using the violet and green magnetic pickup wires unless you retained the '77 distributor and points etc.
I just wrote up the instructions last week to install an MSD in a 1980 engine here:
MSD street fire in 78sc
The guy followed the instructions, reversed the pickup wires as he needed to and it works perfectly...

Yours should be the same except the '77 tach signal wire is not in the 6 pin connector connected to the 14 pin connector. Look for the purple and black wire in a 2 wire "T" connector near the original CDI location and connect that to the MSD output once you have the magnetic pickup sorted, (if that is what you have).

Feel free to PM me with what you actually have and I'll help you get it going and post what was done here.
I'll even chat on the phone with you if needed, just send me your number and when to call in a PM.

[dschloe]

Yes it's connected to the tach lug on the msd then to the tach signal wire on the CDI plug. Timmy2 sent you a PM thanks

[Lapkritis]

The white wire from the msd should go directly to the Porsche black/violet wire on the distributor.

Not sure if you can see it here:



Here's a walk through video of all bay wiring that may help that I took about a yr ago:

http://www.youtube.com/watch?v=oyXjzLv6aU8

[timmy2]

Originally Posted by Lapkritis

The white wire from the msd should go directly to the Porsche black/violet wire on the distributor.

Using the white wire would be correct, If, he is running a '77 style distributor with points....

He has a 1980 engine installed in the car, so I would assume a 1980 distributor which should have the "green wire" magnetic pickup installed.



Knowing the tach signal wire in a '77 does not connect through the 6 pin cdi plug on his 1980 harness is key here. He needs to connect the tach signal output from the MSD (with or without adapter) to the wire going to the tach in the body harness.
On his '77, that wire should be near the old 3 pin CDI mounting location in a 2 wire "T" connector.... (Depending on the wiring mods made to install the '80 harness.)
I recently instructed someone how to re-wire their '77 fuse panel area harness and 14 pin connector so that an SC harness was completely plug and play..

[dschloe]

Thanks for everyone's help on this. Wound up being a bad tach. Replaced the tach and it's working without the 8920 adaptor.

[timmy2]

Glad that fixed it Dave,
Good talking to you on the phone. Hope the cookout went well. I had to BBQ between rain showers here!