Pertronix and Powerspark

[mbell]

In very inaccurate terms, the standard tacho work by "counting" current pulse to the coil. These are normally triggered by the points, so relate to engine speed.

If you power an electronic ignition module off the coil, the pulses relating to its operation also go via the tacho and you can get strange behavior of the tacho. Particularly so with 50 year old electronics in them.

The possible fixes are:
- Don't power the module from the coil, add a separate switched live for it.
- Rebuild the tacho electronics, especially the capacitors
- Replace the the circuit board in the tacho with a RVC one, like spyida. This will also require some re-wiring and calibration of the tacho.

[cbguerrajr]

About 10 years ago, I purchased a petronix distributor already fitted with the electronic ignition components. 100% trouble free, this has been the most reliable part of the car. (Negative ground, sports coil, alternator conversion).
A Lucas-free Elan!

cg

[ivan.wood]

I will update this thread after reverting back to the old distributor with points. Still having rough running issues but that may be nothing to do with the electronic ignition.

Cheers

Ivan