MSD INSTALL and no tach!

Joe911 · 01-23-2002, 04:35 PM

Sounds like a common problem .

Have changed over to the MSD6AL to help improve idle characteristics and the soft-touch rev limiting for autocrossing. Had a Permatune. Wired as per Wayne and MSD - BIG RED WIRE - Power, BIG BLACK WIRE - ground to old CDI mounting screw, SWITCHED RED - spaded to old CDI plug red, WHITE (impulse from points) spaded into old CDI plug black wire going to distributor and tach.

Car runs better - starts immediately, noticeably smoother at idle and up to 2500 - so this must be correct.

However no tach - read the threads but I am still confused. The MSD must change the signal in some way that I don’t understand.

I have tried 4 different combinations:
(1) Leave the black/purple tach wire connected as it was with the Permatune which is to the black lead off the CDI plug that also went to the points. (2) Connect the tach black/purple wire to the MSD tach output terminal. Install the 9210 tach adapter as per Wayne and connect the black/purple wire as per 1 or 2.

Should I run my tach off the negative coil terminal? Probably not as it was run off the distributor. Do I need the ballast resister?

MSD says that if the tachometer was triggered by the coil negative use the tach adapter and if triggered by the coil positive side, use the dual ballast resistor. Which is my 1969 911S? Sounds like I need either the tach adapter or the ballast resister.

I have purchased a generic Borg-Warner ignition ballast resister and an not sure where to install it. Inline on the white wire (points), inline on the red wire (ignition), or tap into both white and red like the tach adapter is installed? I AM GOING OUT TO TRY THIS IN ABOUT AN HOUR….. ANY SUGGESTIONS?

s77911 · s77911's Garage

Are you sure the tach is still good after all your testing. They are extremly easy to fry. Don't ask me how I know this.

jtdig64 · 01-23-2002, 05:30 PM

I installed the 6L on my car. I installed the tach adapter with the module. Mounted it above the msd. My tach would not work until I installed the tach adapter...
Be careful the tach is very easy to fry, ask me how I know this......... The tach feed is the black wire with the purple stripe, off the old cd unit, if I remember right...

Regards,
TOdd

Joe Bob · Joe Bob's Garage

Signal changes from analog to digital,,,,at least that;s the only way I could figure it out with a meter...the adapter installed and boom....got readings.

Joe911 · 01-23-2002, 06:45 PM

SS77911 - Just reinstalled the Permatune and the tach works so no problem there.

Also installed the resistor in the red ign switch line and the line to the distributor .... and bridging them both ...... no difference .... no tach .... scratching head....

TODD - when you used the tach adapter did you hook the black/purple tach wire to the MSD tach terminal or leave it attached to the black lead at the old CDI connector?

MIKEZ - The MSD tach terminal provides a "12V square wave" - according to the directions. This must not be what my year tach wants. Is this where you are referring to?

The MSD must have changed the signal to the distributor as this is where the tach signal comes from the way this is wired. Evidence of this is would be if a connection directly from the distributor to the tach (black/purple) lead works with the Permatune and not the MSD. I could test this and will in a few minutes.

Thanks for the thoughts.

jtdig64 · 01-23-2002, 07:28 PM

Joe,

Attached the wire (black/purple) to the MSD tech module itself. If I remember the tach adapter wired into the MSD module....I think.... I cut the wire to the plug of the old cd unit and wired it into the circuit of the module.

Regards,

Todd

Wayne 962 · Wayne 962's Garage

When I called MSD doing research for the 101 book, they told me the following:

On the 911, you should purchase the tach adapter. On some cars, the tach will work fine without the adapter. On some other cars of the exact same configuration, it won't work without the adapter. Basically, all 911s should use the adapter if you want reliable, consistent tach readings. Other people on this board have also confirmed this as well...

-Wayne

Joe911 · 01-24-2002, 01:50 PM

So I will wire in the tach adapter again as I gather it can not do any harm.

If the tach reads off the distributor on my car, how has the MSD changed the impulses from the distributor so the tach does not respond?

I will experiment more tonight. I will also e-mail MSD. ANY OTHER SUGGESTIONS ARE APPRECIATED.