Fitting a 123 electronic ignition to a 2CV

I made a concious decision not to put an electronic ignition into Judith as I wanted to keep her as original as possible.  However, the majority of the hassle I’ve had with her has been caused by the ignition.  After my first shakedown run this year she was backfiring on the way home and my first thought was the ignition.

After checking the static timing, the dynamic timing (with a strobe gun) and the points gap I couldn’t find any obvious cause.  So then I started swapping out parts of the HT system to check if anything there was out but there was no change – she was still running lumpy and backfiring at about 3/4 throttle when accelerating.

As a final, last resort, check I ran the car with the points box cover off and could see that there was significant arcing over the contact breaker.  This is a problem as it means the contact isn’t being broken properly which will lead to miss-timing and a weak spark.  This is almost certainly due to a failed condenser – apparently a fairly common occurrence with newer condensers.

By this point it was well into the evening and I’d spent the rump of a day going nowhere (well, apart from 100 yards down the road and limping back on one of the shortest test drives I’ve ever done).  I put everything back together and had a think about what to do next with a club run coming up in a week’s time.

As the title of this post suggest, my conclusion was to fit an electronic ignition.  I had already purchased a 123\TUNE+ for the pile of parts I’m intending to turn into a Burton so, a few days later, that was pressed into service.

Fitting the ignition is refreshingly simple as it sits in place of the old points box and is a fully reversible figment.

2CV points box in-situ

The starting point is removal of the old points.  The box comes off with the removal of the two 11mm nuts on either side.  After that the thin metal shield comes out which exposes the timing cam and centrifugal advance weights.  Removing the circlip that holds the timing cam onto the cam shaft allows this whole assembly to come out.

This leaves the nose of the cam shaft showing and the two pins that attached the advance weights.  In the ignition kit there are a pair of sleeved magnets that slide onto these pins, the magnets being strong enough to hold them in place.

Sensor magnets on a 2CV camshaft

The ignition itself then fits on in the same way the points box did and is retained using the old 11mm bolts.

123 electronic ignition in place of a 2CV points box

The red wire is connected to what was the positive supply for the coil, this now gives the ignition a 12v power source.  The black (-ve) and yellow (+ve) wires will be connected to the coil terminals later.

With the ignition powered up the green timing LED on the front can now be employed.  This is identical to timing with a timing light – when the flywheel is at the timing mark, rotate the box until the light goes out then back until it just goes on again.

The black and yellow wires can now be connected to the coil terminals and we’re ready to go.  The difference it made was surprising, starting from cold it caught immediately – even when warm it used to cough once or twice.  The engine note was also noticeably smoother and it needed less choke.

But the fun didn’t stop there.  One of the benefits of the 123\TUNE+ is that it comes with an app that connects to the ignition via Bluetooth and shows a glass dash.

123\TUNE+ app dasboard

This is all well and good for a cold engine idling with a bit of choke.  The problem came with any more revs than this:  the voltmeter pinned itself to the top of the dial (15v).  (Curiously, the voltmeter in the dash that uses the factory connection in the wiring loom was reading about 14-15v – a bit high but not indicative of an issue.)

This lead me to conclude that the voltage regulator was goosed.  From what I can tell, it’s the original Paris-Rhone item that was fitted to the car at the factory.  The somewhat steampunk appearance didn’t add to my confidence in it’s continued ability to function in an efficacious manner.

Steampunk appearance of an original 2CV Paris-Rhone voltage regulator

The replacement item is a fraction of the size of the old one and is a simple swap.

2CV voltage regulator

The ignition now reads a consistent 13-14v confirming that the old unit was indeed past it.*

With everything in place and a shakedown run up and down the road – more than I’d managed last time – it was time for a longer run.  When fully up to temperature and with some fresh dinosaur juice she was running really smoothly.   The accelerator response is right there (although with 29 horses it still takes a while to have an effect on the road) and, most noticeably, she’s significantly happier when coming off the throttle.

For all the trouble it has caused, I’m glad I persisted with the original system – not only do I now have a good working knowledge of how it operates but I fully appreciate the benefits provided by a modern electronic ignition!

* I think that the failed regulator was a significant contributing factor in the previous ignition issues – it will have been over loading the system and may well have over stressed the condenser, especially if it wasn’t the best quality anyway.