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

How did it go Andy?

 

Hi Mark,
All good, thankyou!

My fiddling around trying to find the problem meant a lot of tweaking of linkages etc. to get the car running well - but after a couple of sessions with flow meter and a few test runs, I'm ready to start doing some slightly longer runs.
I was always so confident in this car but that's taken a knock over the last 18 months - a few decent runs will rebuild that confidence.

I posted this up a little while ago, after one of my sessions with the screwdriver:
https://www.ferrarichat.com/forum/posts/149132720/

 

Hopefully the confidence will build again. I have been similar, years of taking the car all over Europe and Scandinavia and now just building up the miles again.

 

Are my coils drawing too little amperage?

Adrian at the very start of this thread posted:
A quick test can be done using a current clamp and measuring the positive (yellow wire) feed going to each coil. At idle you should see around 4-6 Amperes of current (depending on the type of current clamp, e.g. RMS type or standard). If the current is below 4 Ampere for both coils, then there is most probably a problem with the voltage supply (check terminals, wires, ground and fuses). if the current is different between the two coils, then the sensor gap is most probably not set correctly or one of the coils is defective.

With the engine at a steady 1000 rpm idle:

When I put a clamp meter on the yellow feed wires to the coils, I get the following readings:

Front Bank 2.85 Amps
Rear Bank 2.30 Amps​

(The Rear Bank is wired in series with the Front Bank)

The alternator is putting out 14.15 volts - measured at the battery terminals
The coils are 0.8 ohms (new and tested)

Thoughts, please!

 

Thanks Adrian, that is extremely helpful.

 

You might also confirm/deny that the voltage on the positive wire at the coils is also near that same voltage value -- whereas, the alternator is connected to the battery by large wires with few, and very reliable, bolted connections, the path from the battery/alternator to the coils has far more, and less reliable, connections (and if you've "juiced up" the ignition system that increases the current and can degrade them). Probably not an issue, but it's easy to rule in or out without getting greasy .

 

Thanks Steve, yes that's a quick and easy job. I like them.

 

13.6 volts at the positive terminal of the coil. A tiny drop but I don't think it's ignition threatening.

 

+1 -- that's not anything that would cause a problem (but it does show that longish small wires and connections are not 0 Ohms).

 

Hello all,

I have quite a bit of trouble with my engine since I received my car.
First it had a very rough idle and wouldn't properly rev above 3.500 RPM. I took apart the entire ignition, cleaned and adjusted the distributor, got new leads, coils and amplifiers.

I got the engine to work quite well below 5.000 RPM now, but it's still like hitting a rev limiter once the engine revs beyond 5.000. Clearly cylinders drop out, maybe even a whole bank.

I followed the instructions and information in this thread and used Pertronix coils with MAKO amplifiers. The only thing I had trouble with, was setting the gap of the VR-Sensors with a gauge. I set it by feeling the resistance of the reluctor wheel passing and there is 8 clear positions where the rotor has the same resistance during turning - It even "snaps" into rest in one of the positions, if I just spin the shaft and let it come to a rest on its own.

Now I wonder, can the gap be too small (< 0,25 mm) provided there is no physical contact and what would the effect be?
I also measured a dwell angle of ~ 18°, but I'm not sure how well my tester copes with the setup, since It's a 40 year old manual gauge.

I'm really thankful for any help, that gets me in the right direction.

 

Ok...I have an update, which might be of interest to others.

After writing my last post I went back and had another try at diagnosing why the car won't rev. And I realized that with a cold engine (until about 15 minutes of running) everything runs perfectly smooth. No hiccups to the red line at all. Only after everything gets warm are there substantial misfires.

So I measured dwell angle again and got 40° for one coil pack and 18° for the other. I then swapped the plugs for the VR-pickups and leads to the distributor around. However, it stayed at 40° and 18° for the individual coil packs and the angles didn't swap modules. Therefore, I concluded that the error is not within the distributor, but must be in the coil packs. I then swapped the MAKO unit for an old Hella unit and I immediately had a dwell angle of 44° and still 40° in the other pack.

So it seems, that one of the two MAKO units I bought becomes faulty as soon as it reaches a certain temperature. I'll get a new one from Turkey now and see if that is any better.

Is there any word on the Hella units?
It seems the only two options right now are the Pertronix D2000 (which I can't get anywhere in Europe) or the MAKO 79553901.

I'd still be interested, if there is such a thing as a too small gap for the VR-Sensors and what the effect would be.

 

That's very interesting. I am in a similar situation to you.

With much difficulty I purchased 2 Mako units and I am experiencing similar issues to you (but without the luxury of being able to measure the dwell etc.)
I have adjusted the VR Sensors such that all 8 positions are very 'sticky' and I don't believe I could get them any closer to the reluctor.
I actually bought another pair of Hella modules in the hope that maybe the issue had been resolved but they retarded the ignition - I have emailed Hella UK but received no response.

Are you able to purchase Mako units easily? I had to engage a shipping/export company, that dealt with Amazon Turkey - as I don't have a Turkish TR Id. I was then able to buy the last 2 units that Amazon Turkey had.
Can you get these Mako units easily? If you could get some for me I would be very grateful - I would send EUR direct to you.

 

I'm looking to rebuild my AEI200A and wondering if Hella ever came back to confirm or deny the triggering issue?

 

Many thanks for the update @alhbln, it is greatly appreciated. I will investigate the other options.

 

Hi all,

just FYI @Ics19:
Both @Andy 308GTB and I experienced the same problem with MAKO- they become faulty as soon as they are properly warmed up. In my case one of two modules failed, for Andy also at least one.
I ordered new ones and they just cleared customs today. If I have them in hand tomorrow I'll report back next week, If the new one works.

 

Hi,

ok quick update:
I received the new MAKO module and that makes a total of 3 MAKOs I have tried:
1. Production year 2016: Works perfectly fine
2. Production year 2016: Works when cold, develops issues when warmed up (~15 min of driving).
3. Production year 2023: Bank doesn't fire.

Well, makes 1 out of 3 for me...and considering what a hassle it is to get them from Turkey, I really can't recommend it. @Andy 308GTB may have better luck, I'm sure he'll report back as soon as he has results.

I do have good news though. I tried these modules: IM4002S | Ignition Modules (as-pl.com)
For now (50 km of driving - Autobahn, country road and city) those work perfectly. They are very cheap and readily available. My recommendation therefore are those!

Best regards

 

I am wondering if the below coils for better performance if not much downside,,,

MSD Blaster 2 : Primary 0.7, Secondary 4.5K, Turn Ratio 100:1
Pertronix 45011: Primary 0.6, Secondary 9.0K, Turn Ratio 100:1

Any thoughts, please.

 

Hello, where did you manage to get the IM4002S modules from - every where I look are out of stock

 

The coils you mention cannot be mounted sideways, they are oil filled so they must be mounted vertically. The MSD blaster epoxy filled coils can be mounted on their sides.

As for performance, you will not notice much more spark from the stock system. I highly recommend 2 MSD boxes to fire the points system. The points will last longer and the ignition is of course far superior. You will need a tachometer adapter if you go this route

 

Have you checked your timing?, it has been problems with diffrent brands of ignition modules with retarded ignition,Hella is one of them, this Pertronix D2000 have been tested by many owners and seam to work very good, by the way, i read that you have a 78 sprintpack?, i own a 1979 GTB sprintpack., i also have the stock Marelli AEI200 Iignition and it works perfectly, it supply a strong and good spark and if manatined properly will give good service.

 

Regarding adjusting the gap, should it be possible to measure the diameter of the rotor and then make a excact copy with snugg fit axle in a lathe, make it in alu or hard plastic, drop it in then measure the 0,25 gap, take it out and drop the rotor in, doing this will make it excatly correct.

 

Hello Adrian

If you are still around .... you were helping me here with a '79 Euro distributor about 1-1/2 years ago. Back then I became discouraged and confused about how to set the VR gap or check the output and the distributor has just been sitting in my office ever since. Poor car!

So recently I built a test stand and bought a cheap ebay pocket o'scope to see if i could test the 2 VTs, and I think I have. If my 'attached image' actually gets sent, the left trace (marked front bank) shows a much stronger trace than the 'rear bank' trace (and it was a weak spark on the rear bank plugs that started all this. But my question now is: is the VR (you said probably original) bad and should be replaced, or do I still need to try and figure out how to set the gap?

Resistance is 803 ohms front and 799 ohms rear with my voltmeter. Rotating the shaft to detect a slight hesitation when VR's pass reluctor just makes me feel like an idiot (maybe something; maybe imagining it).

Thanks in advance if you get this and can again help out.


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Hi @308inTex - they're some great traces I've seen similar to your front bank in my setup, but for the same rpm (frequency), I was only seeing around 40v peak-peak when I measured the gap at 0.2mm. Not saying my readings are correct, but it would be worth checking your gap as possibly it's closer than it's needs to be as looks to show over 80v? As a comparison, when I set the gap to 0.4mm, the peak to peak dropped to around 20v. However, your rear signal has a worrying glitch as it crosses from negative to positive - I'm sure this isn't helping things as the module will likely mis-trigger. This could be a faulty pickup and/or module - if you can swap the modules between the front and rear then it should give you a clue as to where the issue lies, i.e. if the glitch moves to the front then it's the module, but if it stays at the rear then it's the pickup. Can you post pictures of your test rig as that's definitely the way to go