intermittent misfire

[Learjet]

I hope this may help others.
I have had a series 1 1.3s sport for over 2 years and until 3 months ago it had a very annoying intermittent misfire every 5 or 10 minutes. I went through everything to no avail. It would just completely cut out for a nano second.
I do not like night driving as with no relays the headlights are very poor. Recently I had to drive at night and after a while realised that there was no misfire.
Tried it during the day.....same. Lights on fine but lights off a misfire.
It is a case of the analogue and the digital not working well together. I run a dynamo with a Bosch VR but also a 123 electronic distributer. The 123 is very sensitive to over volts and the voltage regulator was overvolting and cutting out the 123. With the lights on it drops the voltage enough for the 123 to be happy.
I am guessing the contacts in the VR just need a good clean. I will get around to it, but Lancia very cleverly mounted the VR in such a position I have to remove the bonnet to access it. Easy I know as it is aluminum, but my garage is tight for space.
Be interested to hear if anyone else has had a similar experience.
Goodwood track day was brilliant in 2021. I missed this year, but I hear it was another success. I'll be there next year
Cheers
Simon
Yellow Zagato

[marnix]

I understand it is S1 Fulvia with a dynamo. I would highly recommend replacing the electro-mechanical VR with an electronic equivalent. The old VR with the relais that keep going on and off at high rate are a bit of a danger: if one gets stuck, you may burn out your dynamo or even have the battery explode (overcharging). There are electronic Bosch VR that are good replacements, and they protect your dynamo and battery.

[Huib]

As Marnix says, replace VR with the Bosch electronic one. Careful as the case carries the raw voltage from the dynamo and serves as a heatsink for the diodes.

An old electromechanical VR may burn your dynamo as happened to me or rather to my car once.

It is a good idea to also have the dynamo checked by a specialist shop. They have to equipment to check if all the windings are working and other useful test equipent.

Spiking can also occur on S2 / 3 cars which have an alternator.

[Learjet]

Hi
Thanks for the advice about changing the VR for a Bosch electronic. To save me hassle and to ensure I order the correct one, does anyone have the part number? It is a 1968 series 1 Fulvia sport.
Cheers
Simon