MSD Tach Adapter not helping
 

Installed the MSD tach adapter #8910 to my 69T.
Have the MSD 5 and a Blaster 2 coil.

No difference. Tach still doesn't read below 3000.

Any tips?

Jim

You might need to include the diode as shown on the right side of this circuit diagram.

http://forums.pelicanparts.com/uploads/MSD.jpg

What does the diode do?

Had the same thing with my 67s when I put the MSD on ,I bought the tack adapter and it did not work also, sent the tack to North Hollywood Speedometer (818)761-5136 They handle this all the time knew what to do and made it work, Fritz

If you are still using points to trigger the tach, split the signal and send it to the ignition and also the tach. This works with points, pertronix or a Crane optical setup. The tach will read that 12V signal just fine.

I tried a tach adaptor and it never worked for me either.
I ended up sending my tach out for MSD conversion to
North Hollywood.

Can someone comment on how much the "MSD conversion" from North Hollywood cost?

Thanks,

I had mine done recently.

$150.00 + $10.00 shipping

Add $20.00 and you can the face of your tach changed out to 10,000 RPM if you plan to modify your car in the future and need higher rpm's.

Talk to them and ask

I just ran out and split the signal from the points like JPnovak suggested and it worked. One wire plugs into the purple/black tach line the other into the white wire. The Tach adapter is still wired in and strangely the whole thing wouldn't work without it. Thanks, for the advice, Sam

I have a tach out of a 69E that had this MSD mod done (It works cuz I used it). I do not have any use for it now since I upgraded. I will sell it for $100+ shipping if anyone is intrested. Its in good shape.

Can someone alter the wiring diagram above to illustrate what they did to make this work, I have the silly tach adapter sitting on the work bench since it never helped fix the magical bouncing tach.

Please give as many details as you can (my car is a 71)

Thanks,

Spud. That's a diagram that I made to record how I made my system work with the stock (unmodified) tach. It took me a little bit to get there with the help of the MSD people. Sure you can send your tach out for $100+ to get it updated, but I suspect that all that they do is add the diode internally to the tach. I didn't see any reason to waste the money since the diode comes in the bag of little odds and ends that come with either the MSD or the Tach adaptor. So the diode was "free".

As far as what the diode does, I'm no EE, but I believe in this application the diode is used because it only allows current to travel in only one direction. So when you install it, you might need to try it both ways to determine which is the right way.

Yup - that's what diodes do. My guess is that it stops the neg. going pulses from getting thru, while allowing the + going ones (which are half the total)....

Info on my tach for sale with MSD upgrade.
http://forums.pelicanparts.com/porsche-911-used-parts-sale-wanted/206836-fs-1969-911-e-tach-good-condition-msd-upgrade.html

http://forums.pelicanparts.com/uploa...1108605200.jpg
Here is the altered diagram. This is what I did to my wiring today to make the tach work. Before I had the tach wire hooked up to the positive terminal on the coil and was getting triple readings below 3000rpm. This is exactly what JPnovak recommended. Hope this helps. Sam

If I want to split the points line to lag into the tach, where in the engine compartment do I pick up the tach line?

http://forums.pelicanparts.com/uploa...1108612637.jpg

Instructions for the diode installation. Be sure that the male end is toward the MSD unit and the female connector is toward the tach adapter, tach wire and distributer connections. In my 69E I had two black/purple wires. One went from the CDS unit to the RPM transducer. The other from the Oscillationg SCR to the tach. If you tie into the black/purple going to the Rpm Transducer your tach will never work. You must disconnect the tach wire and tie it into the white wire with the adaptor and diode. Funny, my hand held tach/dwell meter was able to read the tach output of the MSD unit but the car's tach couldn't. The reason you need the tach adaptor is that the white trigger wire for the MSD is just a ground-no voltage to it. The tach adaptor adds 12 volts so the tach can see the signal. Hope this helps.

Jim

I got the MSD and Tach Adapter from another Pelican. I don't have the diode that would have been included.

Does anyone know if I can pick one of these up at Radio Shack?

I'll call my local performance auto store tomorrow.

Jim

You dont need the diode. At least I didn't. Just plug the split line from the points into your blk/purp wire going to the tach. My wire is blk/dashed purp. and the other into the white line with the tach adapter wired as in the schematic. This should work for you. Sam

Thanks Sam

Now to find the tach wire...

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

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

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

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.

http://forums.pelicanparts.com/uploa...1108742967.jpg

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

Post the pics.
Sam

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.

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

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

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

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