Rebuilding the 308 electronic ignition (SM805A distributor, Marelli AEI200 Ignition)

Bugger. Just bought these and finished fitting with new coils. Just waiting for dry weather to test drive!!
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Thanks for the heads up though!

 

Hi Adrian, this is very, very interesting.

This may help you (and me).

My car developed an intermittent fault towards the end of 2021. It would fire up fine and drive normally, freely revving to the limit.
But every so often it would simply not rev beyond 4,000 rpm. After anything between 30 seconds and 5 minutes, it would suddenly clear and if my foot was on the throttle it would leap towards the rev limiter. This became more & more frequent and more prolonged, such that I couldn't drive the car and I garaged it.
i.e. the exact same symptoms you are describing. I have gone down multiple rabbit holes trying to track this fault down (I described this exact malaise in this post dated April 2022 https://www.ferrarichat.com/forum/posts/148487541/)

I have subsequently replaced the following:
- Plugs
- Plug Leads
- Distributor
- Rotor
- Coils (see my next post)
- Ignition modules
I have had the curve checked and it's spot on. I only got the dizzy back this weekend and I am currently re-installing all it. I hope to have it ready to fire up in the next week.

The key part of this, is that the intial fault (end of 2021) was on the ignition modules that were 7 years old (?) - you will remember that saga

 

As part of my saga (see previous post) I bought the Pertronix coils. They have an internal resistance of 1.5 ohms.
The guys who tested my ignition pointed out that the Bosch coils and Beru coils have an internal resistance of 0.8 ohms and suggested that these were better suited to this ignition type.

I have taken their advice and I will reinstall the Beru coils.

 

I did subseqeuntly realise the significance of the 'order of preference'.

 

I had no luck finding Bosch or Beru coils so ended up with the Pertronix. Now you've got me concerned.



To top off the saga, after reading the Hella amp issues, I have ordered another set from Superformance that were not named at 3 times the cost. And you guessed it, Hella amps turned up.



I don't know what to do now.

 

The car started, idled OK, but would not rev.

I've bench tested the resistance of the coils old and new with the following results:

• Marelli Coil - Primary 1.1 ohms, Secondary 10.3 ohms
• Pertronix - Primary 1.7, Secondary 9.3

I also put the tester across the amplifiers with interesting results, although I'm not sure if this is how to test these:

• Marelli - WC 1200/1700, WB 14.4/17.9, GB 104/125, GC 1290/1900
• Hella - WC 0, WB, 14.7, GB 30.7, GC 0

Both Hella's as fitted (HELLA GmbH & Co. KGaA) and the subsequent Superformance supplied items tested the same. Would be interesting to see how other modules test. I have an enquiry in with a UK Pertronix supplier to discuss and will share the outcome.

 

I can't edit my post above, but have been corrected on my use of a multimeter and so the Primary results are actually 0.7 & 1.3 respectively

 

I placed the multimeter across the terminals to read the resistance. Only similarity was the reading through terminals W to B. Don't know if this is the right way test these but the results were:

• Marelli - WC 1200/1700, WB 14.4/17.9, GB 104/125, GC 1290/1900
• Hella - WC 0, WB, 14.7, GB 30.7, GC 0

 

Hi Adrian,
My assumption was that the Ignition Modules sole purpose was to detect the pulse from the VR Sensor in order to trigger the coil & that the SM805A mechanism advanced/retarded the ignition.

But you are saying that the faulty Ignition Modules are causing the ignition to retard?
I ask because when I put a timing light on my car, my ignition is retarding as the revs increase - as you describe. These are new Hella modules purchased a few months back.

The alternative ignition modules appear to be out of stock although I did find some generic replacements on eBay.
https://www.ebay.co.uk/itm/155195546937?ssPageName=STRK%3AMEBIDX%3AIT&fromMakeTrack=true&mkevt=1&mkcid=1&mkrid=710-53481-19255-0&campid=5336838664&toolid=10001&customid=lb5ne7x620000k3x00003

 

Thanks very much for the update Adrian, it's much appreciated.

 

Good work, thanks for the update

 

Thanks very much Adrian. I have found a handful of sellers (in Turkey) and have messaged one already.

 

Hi Adrian, how did you obtain that module?
I've had an entertaining week using Google Translate to communicate with an outlet in Turkey. The parts are in stock, the price is reasonable but the website only allows the country 'Turkey' to be selected for delivery.
My efforts to explain the problem are met with 'TM' - which I think means 'OK' but could mean something much more colourful!

This is the link to the part:
https://www.aktasotoyedekparca.com/urun/elektronik-atesleme-modulu-dogan-kartal-sahin

 

Just identified another seller but it only allows orders to be placed if you have a Turkish telephone number...
https://otosunaryedekparca.sahibinden.com/

 

I finally managed to buy 2 Mako ignition modules from Turkey. These were the last 2 on Amazon Turkey (note the mismatched boxes). Buying from Turkey is a battle and a Forwarding/Shipping Agent is required.
I hope to have these on the car by the end of the week. I'm praying this is the end of the saga!

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