924Board.org

[MOTANUL]

Greetings!

Ref. to Porsche 931 S1:
93160203000 (Distributor) and 477905351B (Switch unit/ Engine Control Module / Ignition control unit Bosch / Control unit transitorized ignition).

For a long time I noticed that I had a weak spark. (about 50% of normal).
With the strobe lamp I saw that at certain speeds certain sparks were missing. (few - most are present). ~ 2500 PRM.

I thought I would check first ignition Distributor and Control unit transitorized ignition + and the electrical connections between them.

What do you advise me to do next? Is there a tutorial on how to disassemble the ignition Distributor or how to repair the transistorized ignition?

PS: One thing is clear: In transitorized ignition at some point water-moisture entered and make some damage.


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1980 Porsche 924 Turbo (931) diamond silver metallic/helios blue metallic
sold Porsche 924 NA 1979

[Eliza]

That circuit board doesn't look so healthy

If that TIU were mine, I'd try reflowing the solder on the circuit board, see what that does and go looking for a spare just in case.

Eliza
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1985 924 NA RoW
1981 931 S2 RoW

[MOTANUL]

However, it is a miracle that the car goes the way the circuit board looks.
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1980 Porsche 924 Turbo (931) diamond silver metallic/helios blue metallic
sold Porsche 924 NA 1979

[louis_wahl]

Hi MOTANUL,

Could you solve that problem? I have exactly the same issues.
It would be awesome if you could reveal the solution.

Yours,
Louis from Germany

[morghen]

Forget hunting ghosts, get an EFI kit from me instead


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Supercharger and EFI kits
https://www.the924.com

[Beartooth]

My bet is you could repair a damaged ignition module like that for around $10 - if you had some familiarity with soldering and working with circuit boards. Typically on circuit board repairs like that you want to replace all electrolytic capacitors, plus any other components that appear damaged (what looks like the main input resistor on the board pictured is damaged; it may be limiting current, which would explain the weak spark). Now, it's kind of a pain to source the electronic components needed for such a repair. Here in the US, the only common store that carried electronic components - Radio Shack - has pretty much ceased to exist, and they were limited in what they carried anyway. Not sure how it is in Europe, but you're probably left ordering what you need. Still, with a little knowledge and a soldering iron, they can be fixed, and no need to pay the outrageous costs for a refurbished unit.

If that's not appealing, the next option is to buy a used one. Mine's original, as far as I can tell, and works fine; they seem to hold up well if they stay sealed. I think it's used on cars other than just the 924, so look by the Bosch part number. They're showing at around $100 on ebay here. If you could find it from a wrecker/dismantler or private party sale, it'd be cheaper... Obviously, you're taking a chance even on one that's "tested," so you'd want to be able to return it. The last option would be to do a Pertronix conversion or something similar. That may require finding a different distributor though; I see one listed for earlier 924s, but it's probably for breaker-point distributors. I'm sure with enough knowledge and/or parts for Bosch distributors, you could make it work, but I'd want a breaker-point unit on hand to swap parts from. Also, you'd have to keep the 931 advance/retard mechanisms or you'd cook your motor... Anyway, there are definitely ways to fix the problem without spending much, and if nothing else, I'd see if I could find a good used one.
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1980 931 diamond in the rough

[MOTANUL]