Marelli Misfire

[EvanR]

Hi Guy, I am running a 131 2L in a lada 2107 and am having major problems with the marelli electronic ignition.
The engine is recently totally reco . The ignition consisted of the standard 131 coil a new Etron duralife module, new copper leads, new distributor cap and new bosch plugs.
On first starting after reco there was so much spark that the plug porcelians were glowing from the arcing. The copper leads were replaced with new bosch supressed leads which seemed to work. A week later the new duralife module fried itself and was replaced by a standard Fiat part. All was going well then I changed from a adf carb to a pair of DHLA's using a 125T manifold with the scollap in number 1 runner. The cap and leads were arcing across to the manifold so a plastic shield was made to isolate the two. The car ran excellently for about 4 weeks but then began running on only 2 cylinders -numbers 2 and 4. At night it could be seen that there was arcing between the distributor cap turrets and when an earthed wire was placed within an inch of the cap an arc would jump the gap. The cap and wires have been checked and no evidence of tracking splits or cracks are evident I would really appreciate any ideas you may have on this.

So the Marelli was removed and replaced with a Bosch electronic ignition out of a 132 2L so far it seems to be working ok but has a total different feel than the Marelli . The Marelli when it was working was instanteously manic when you put your foot down but the Bosch is a smoother but more subdued. Could you tell me if the curve is much different between the two systems? Also I was told that there is a cap off a peugeot that fits the bosch has side exiting leads can this be used with a side draft manifold.
thanks again for you help
Evan

[Guy Croft]

Both ignition advance curves are the same and they are generated by the distr no the power packs.

Both units MUST be hooked up to their respective OE spec coils and the Bosch must have a ballast resistor. The Marelli power pack can exhibit erratic firing as the power pack on the back of the heat sink gets on in years. The Bosch in my exp is the more reliable of the two, I have never known one go wrong. Both units have pickups in the distr which can go wrong.

Beyond that I cannot explain the odd behaviour except to say if the insulator is getting that hot it could be be a combustion chamber event, perhaps chronic over-retard or firing at the wrong time in the cycle (ie: all over the place). I would be for taking the head off and making sure you have not been having chronic detonation.

G