MSD install on 1.7 D-jet: no tach...anyone...?

MarkRobinson · 03-24-2008, 11:35 AM

I got my optical pick-up & MSD 6A & blaster coil installed on my 914, but have lost my tach signal.

Originally, the coil had a single + black wire to it, & a pair of wires on the - terminal: green wire from breaker points in distributor, & black/purple-striped wire as well. All are connected, & connected semi-correctly as the car runs ok (though some ignition-off run-on is noted).

Pointers??

Mark

John Rogers · 03-24-2008, 07:37 PM

Try a voltage check at the coil terminals when running and if I remember correctly it is over the normal 12 volts. That will prevent the correct signal from going through the black/purple wire.

MarkRobinson · 03-25-2008, 06:00 AM

Hmm, well the MSD box has a tach-outlet too, I should check that as well with a volt meter after I restore the original coil for volt-testing.

URY914 · URY914's Garage

I have a friend that had this same issue with his MSD set up. It of course can be fixed but I can't tell you how. The MSD system is not the best thing to use on a T-IV.

MarkRobinson · 03-25-2008, 07:03 AM

I have to admit that the MSD REALLY Makes the car run smoother & a bit more powerful.

I have a new distributor, trigger points, breaker points & condensor, cap, rotor, wires, plugs, original coil. I felt me spark was pretty weak, the MSD confirms that, though no hard evidence.

Also, I hadn't started the car in a month or so, so with the optical pick-up (trying to set initial timing to start the car), I couldn't get the car running on more than 2 cylinders or so as I fouled plugs doing this.

Once I connected the MSD, wallah, no more fouled plugs: huge difference in idle "power".

Like-wise, modern cars probably do not benefit from advances in ignition technology: I tried an MSD 6AL & Coil on a 944 turbo once: nada. No difference in anything, not even dyno. A slight improvement with the Crane HI-6 setup, but a much, much hotter spark too.

Mark

degreeoff1 · 03-26-2008, 03:16 AM

you need the tach adapter....MSD sells it. End of story.

R_Davis · 03-27-2008, 06:54 AM

I have a new distributor, trigger points, breaker points &
Does't an MSD eliminate the need for points?
Or am I misunderstanding what you wrote?

MarkRobinson · 03-27-2008, 07:00 AM

You still need points (breaker points or an optical pick-up conversion) to trigger your coil or your MSD.

My point was, everything electrical in my ignition system is new, so were the points, & still had a weak spark. MSD made a nice difference: MUCH smoother, & noticably more power. I recommend it. The optical pick-up removes the points & puts a maintenance-free triggering mechanism in the disty.

degreeoff1 · 03-27-2008, 08:06 AM

Mark you NEED the tach adapter, it is $125 dollar item (or so) I KNOW this because I too once had MSD and it WAS ness for a working tach. That is the END of story.... if all you want is the tach to WORK buy the tach adapter...its easy to install and AGAIN you NEED it.

Josh

R_Davis · 03-27-2008, 04:45 PM

I figured as much, Mark. But I had to ask. I would be the one to screw up the installation.

Does the magnetic sensor replace the rotor and spin around inside of the disty?

I have been wanting to investigate MSD system further. Some of them have a hook up for a laptop computer with optimum software settings (models) that allow you to adjust an engines performance for speed, fuel economy, terrain, weather, God only knows the limits.

Also, I understand that if you were to hook up the magnet and sensor on the impeller housing (someway) you could pull the disty; shaft and all, and throw it away.

Those systems run about $1500 and up.

Good luck and keep me posted on the progress.

Rick

Dave at Pelican Parts · Dave at Pelican Parts's Garage

If you're going Pertronix (or Compufire or similar Hall-effect triggers), the magnetic wheel goes under the distributor rotor, and the sensor is attached to the points plate in that same area. If you're going optical (like Crane), the optical shutter goes under the rotor and the LED/photodiode setup gets attached to the points plate under there.

Going to a crank-fire system is a little more complex than simply setting up the sensors on the fan or flywheel end of the motor. The ignition system generally needs to know more than just one signal every crank RPM, so there will typically be toothed wheels with one or more missing teeth so that the ignition can figure out not only when TDC#1/TDC#3 are, but also so they can see how fast the engine is spinning without waiting for a whole crank revolution. Plus there's all of the electrical controls, the ignition advance curves, etc.

--DD