MSD Tach Adapter not helping

[copper]

Okay, as I said, I have the msd 5.

Red wire to + on coil
White connected to points
Orange to - on coil
Black to ground.

There is a black wire connected to the coil - which goes towards the backseat/firewall.

Where will I find the tach wire, or connection to use to run a secondary feed from the points?

Jim

[copper]

As the white points wire was originally connected to the coil negative, if I run a second line from the points output to the coil negative, will this work or will I blow things up?

Jim

[sammygon1]

No that won't work. The whole point is to avoid the coil since it is waht is receive the multiple signals fromt he MSd to fire, which is what screws up the tach. The wire from the points needs to go directly to the tach. Sam

[jpnovak]

HMM I see part of the problem. You have a 69T and AFIK it did not come with a CDI from the factory (only E,S for MFI). So your wiring will be a bit different.

The wire going to the tach is usually a black wire with purple dashes/stripes. Find this wire in one of the 6pin connectors on the rear suspension cross member. Trace it as far as you can. You will also need to locate the black wire from the points. You will need to make a pigtail to splice into these wires. it will need to have two wires with individual connectors on each end and the other two wire ends crimped into a single connector. The male/female faston connectors work well here. Just make sure to get the insulated ones.

Somewhere the black wire from the points should connect to the black/pur wire to the tach. Insert you pigtail here. Then take the loose wire off the pigtail and run it to the white wire on your MSD. other connections are the same.

I hope this helps.

[copper]

I really appreciate all the advice, but I am still at a loss when it comes to identifying the tach wire.

My 69T has no CDI. Straight inductive ignition.

The setup as it was originally had the black points wire to the coil + with the 12V power. The coil - had a black wire, presumably ground.

There was no blk/purple wire in this setup. But the tach always worked.

Now, with the MDS 5 unit, The black points wire goes to the white msd wire, the msd power goes to coil +, the main power goes through the ballast resistor to coil +, the msd orange goes to coil - and the msd black goes to ground. Still don't see the tach connection. Oh, and the thick black is still on the coil -. Again, presuming this is ground.

There are no other wires to the coil or dizzy, so where on earth is the tach getting a signal?

I do see a wire in a two into one splitter with the power lead. This wire is either blk/blu or blk/purple.

I can take photos if anyone has the time to look at them.

I'd really love some help, cause I am lost.

Thanks
Jim

[sammygon1]

Post the pics.
Sam

[Howard M]

Try coming off the points wire (black?) that you have going to the white MSD signal wire. The same signal from the points that controls the MSD will signal the tach, just as it did before you installed that MSD. You can pick up the tach wire at the tach or back at the rear fuse panel. I don't know if the tach wire was black/purple in your early 911 (mine is '76). I'm concerned about the main + power point you chose. MSD recommends going right to the battery or starter with their heavy red wire. Good luck.

[jstobo]

I have looked at an old electrical diagram that seems to be how your car is wired. The black wire from the negative(-) side of the coil goes to your tach. A black wire also goes from this - side to the points. So in your inductive system, everytime the coil fires it sends a signal to your tach and the points opening breaks the circut and makes the coil fire. With the MSD this is no good because the coil fires more than once per point opening at low RPMs. Take the original black wire the is attached at the coil - and hook to your white MSD wire going to the points. The black wire from the coil to the points will not be used. You will still need the tach adapter because the white wire in the MSD circuit is a ground wire. In other words, in your old system the points had 12 volts on them, charging the coil and when they open the loss of voltages causes the the coil to fire the stored up electrical energy.In the MSD circut the points are just a ground and when the ground is broken the MSD starts firing since it builds up electrical charge from the battery and stores it in the capacitor.(hence capacitive discharge ignition.) The tach adaptor adds twelve volts back to the signal wire so your tach can read the signal. I had to use the diode, otherwise the tach bounced around a lot. Hope this helps. I just did this on my 69E but I had the black purple wire form the old CDI ignition. By the way, in Porsches ground is always a brown wire unless somebody has changed it.

Jim

[iamchappy]

I believe the MSD 8920 is the correct tach adapter to use.

[copper]

Thanks for the help guys.

jstobo;

From what you can see from the diagrams (my Haynes manual only has the E and S for 69) do you think it's possible to run a second line from the points and splice into the black wire going to the coil neg?

Is there a way I can test this line to see if this is where the tach is getting signal? ie// sending low voltage through it and watching the tach for movement?

I'm not great with electical. I once changed a light fixture in the bathroom without turning off the breaker. Was neat when the live line hit the fixture metal I was holding... Duh.

Jim

[jstobo]

Jim,
I looked up the MSD 5 installation diagrams. Nothing should be on your - coil side but the orange MSD wire. The black tach wire splices into the MSD white wire that goes to the points. The MSD 5 gets its power from the + side of the coil which your ignition should be hooked up to. The black wire from the - side of the coil to the points must be disconnected. You do not need it any more. The white MSD wire replaces it. Splice your tach adapter white wire into the white wire coming from the points. The tach adapter red wire goes to a 12 volt source. Your rear fuse box is ideal here as a source.

So leaving the points connecter on the distributer should be a white wire,connected to the black tach wire, connected to the white tach adapter wire then connected back to the white wire going to the MSD box. Sounds like a lot of connections but MSD makes it easy for you with the way they supply the wires. You will need to cut the white wire from the MSD unit and put the appropriate connecters on to hook up the tach wire and tach adapter. If you add the diode(i Did) more connections are needed. By the time you finished you will be good at putting on wire connectors, E mail me if you want. Its 6 pm my time tonight. Give me your phone number and I can call to walk you through it if needed. Good Luck.

I am also a

Jim