no spark perma-tune? (long)

[Tuckahoe911t]

1970 911T with three- pronged permatune.

Alternator light came on so I replace the voltage regulator. Still not fixed, battery drained and had to jump start car so had alternator rebuilt. After putting alternator back in car it won't start. Checked all wiring in relationship to the alternator and adjoining area; checked and cleaned all connections. Has gas no spark at plugs or coil.

Searched bulletin board for ignition problem related posts. I have performed the following checks:

1. permatune bench test as recomended by manufacturer PinA-D:3260 Ohms B-C:101 Ohms D-Mounting Flange: 0 ohms

2. 10 Volts to permatune pin B

3. continuity checks PinC to Distributor points; PinA to + terminal on coil; at closed points.

4. Ground checks on coil, distributor, permatune, also general grounds at battery and engine.

5. Replaced leaking bosch coil with new permatune coil (later bench test on bosch coil found it to be ok)

6. cleaned up rotor cap and contacts which is in good shape and appears almost new. Points look good, no corrosion or pitting.

7. Checked voltage output from permatune PinA to + coil terminal. Read on bulletin board that it should be 400 Volt pulses during cranking. Got nothing.

8. Tried Jumpstarting as seemed to help other pelicanhead with similar symptoms, still no spark.

9. connected new HT wire from other vehicle to coil. Although not factory spec. would still expect some kind of spark.

Is this the permatune or is there something else that could be wrong with the car?

Do permatunes fail even if they pass the bench test?

If I send it to the folks at permatune do they run more xtensive diagnostic tests in addition to the bench test?

If it is the permatune, could I have damaged it when installing the new voltage regulator or rebuilt alternator?

Any help would be much appreciated as I am at a total loss of what to do.

[Early_S_Man]

Is this an older blue anodized-case model or a newer aluminum finish box?

The only comment I can make at this point is that 10 Volts sounds a bit low to be trying to start the car with ... a fully-charged battery should be reading 12.8 Volts or better.

Another test you can do is a full, powered dynamic test on a bench using the 'telegraph key' method [trigger wire is repeatedly touched to ground and interrupted] instead of a distributor to trigger the CD unit. The following thread has a Bosch test document posted in it:

Perma-tune CD or Bosch CD?

The Permatune-recommended 'bench' tests are by no means comprehensive, as all you are testing is the pullup resistor at the trigger input and the bleeder resistor across the output capacitor. So, yes, the unit can indeed 'pass' the bench tests ... and still be defective.

I suggest removing the CD unit from the electrical panel and then removing the top cover to see if the electronics are potted in epoxy ... most aluminum-finish Permatune boxes are, but some have been found that aren't. The blue boxes aren't potted, and can be troubleshooted with traditional test equipment, i.e., multimeter and oscilloscope. The circuits are traditional, discrete solid-state electronics.

[jtkkz]

I had many problems with my perma-tune before.

I switched to MSD-6AL , No more problems.

[Tuckahoe911t]

Thanks for the help, the permatune is a newer aluminum finish type. I thought that by jump starting the car over come the low battery voltage problem. Is this not the case?

[jtkkz]

In my 73 911T before, I had spark going into the box but nothing coming out.

It was very frustrating as my car stalled many times.

Finally I removed it and installed MSD, problem solved.

[gadams]

Yes the perma-tune can pass the test and still not work. I had a perma-tune and went through the same steps except my perma-tune was an 8 pin. My perma-tune was flaky it would work some times and others it would not but it always passed the test as per the mfg. I replace the wiring harness and coil without any luck so I did not bother sending back for testing and went looking for a bosch unit.

I recently replace the perma-tune with a bosch and my problem has been resolved.

you should be able to find a used bosch unit from 75-200.
check ebay or this board


greg