Disconnecting coil = Damage to that bank's Digiplex? | FerrariChat

Disconnecting coil = Damage to that bank's Digiplex?

Discussion in '308/328' started by dave80gtsi, Sep 16, 2017.

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  1. dave80gtsi

    dave80gtsi Formula 3
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    #1 dave80gtsi, Sep 16, 2017
    I dropped a bank of cylinders in my 2Vi today, and will be diagnosing what's up tomorrow.

    I am 99% certain that the failure of the one bank to fire is ignition related, so my question:

    For a quick and easy preliminary understanding of which bank has failed, I'd like to disconnect first one wire and then the other from the distributor to the coil for each bank. For the brief period of time that the engine will be running (or not) under this circumstance, is there any potential for damage to the Digiplex for the unconnected bank due to the coil being temporarily disconnected?

    Thanks - DM
     
  2. JV's89

    JV's89 F1 Veteran
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    #2 JV's89, Sep 16, 2017
    I don't know the answer to your question, but I'm curious; would a timing light do the trick?
     
  3. waymar

    waymar Formula 3

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    #3 waymar, Sep 16, 2017
    Could be the distributor rotor. Could be a pick up coil. Check it with a timing light.
     
  4. ME308

    ME308 Formula 3

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    #4 ME308, Sep 16, 2017
    no

    but be very careful if you plan to disconnect a coil wire while the engine is running - safer, if you do it before starting
    (engine will start and run on the working cyl bank without problems)

    next steps would be: swap coils, swap digiplexes
    if the problem stays on the same cyl bank, check distcap/rotor, then tdc sensor of the suspicious bank

    but I`m sure you know what you`re doing ;)
     
  5. dave80gtsi

    dave80gtsi Formula 3
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    #5 dave80gtsi, Sep 16, 2017
    Thanks for the thoughts and replies. I think that I will try to remove and ground the spark plug leads from the rear head first, before I try to crank the engine, rather than mess with the coil leads. Then repeat for the front bank.

    Pretty certain that the problem is with one of the distributor rotors due to earlier related work - will report back with my findings.

    Thanks - DM
     
  6. Dr Tommy Cosgrove

    Dr Tommy Cosgrove Three Time F1 World Champ
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    #6 Dr Tommy Cosgrove, Sep 16, 2017
    I know you's is set up differently than mine but when I lost the entire front bank on my QV is was a crank position sensor. It failed because it was 20 years old. I went so far as to install new coils before I realized what the problem was.
     
  7. andyww

    andyww F1 Rookie

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    #7 andyww, Sep 17, 2017
  8. Ianbrit

    Ianbrit Rookie

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    #8 Ianbrit, Sep 17, 2017
    I had the same problem with my 82 when I first got it. I replaced all three crank position sensors and that fixed it. However before that I replace the coils as well. My car has just started dropping a few cylinders on warm start up. Ive got new caps and rotors to try. If you go the crank position way get ones for the alfa 164, they are the same as the 328 ones which seem to be the only ones you can get. They cost a third as much, you just have to slightly modify the bracket it has. Good Luck!
     
  9. dave80gtsi

    dave80gtsi Formula 3
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    #9 dave80gtsi, Sep 22, 2017
    Update:

    When I first posted this thread, looking for a quick and simple way to determine which cylinder bank was not firing, I did not rely upon enough of my senses.

    Begin with a cold engine. Start up engine, and verify that it still is running on only one bank. Smell strong raw gas from the exhaust, so not a fuel problem. After 10 seconds, shut off engine. Touch rear header. It's hot. So the dead bank is the front one. Easy.

    Open up front distributor. See broken bits of rotor lying inside the distributor cap. Aftermarket rotors, bought 5 years / 1000 miles ago from Superformance UK, changed back then as a part of a routine tune-up. Replace broken rotor with one of the OEM's saved when removed back then. Button it all back up. Take car on 20 mile shake-down trip. All is good.

    Does anyone know where we can get OEM grade 2Vi rotors today? This Superformance one just broke apart after what seems to me to be a limited amount of use.

    Thanks - DM

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  10. Dr Tommy Cosgrove

    Dr Tommy Cosgrove Three Time F1 World Champ
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    #10 Dr Tommy Cosgrove, Sep 22, 2017
    That exact thing happened to me in my Alfa Spider last month. Car just backfired and shut off. I had no clue.

    Turned out it was a busted rotor like that. Never happened to me before on any car ever.
     
  11. kcabpilot

    kcabpilot Formula 3

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    #11 kcabpilot, Sep 22, 2017
    I had to finally ditch the breaker points on my Alfa because of two back to back failures of brand new condensers. The wire just completely popped right out of the canister and the points burned up. So I installed a Pertronix module and haven't had a problem in about four years now. After-market parts quality is very sketchy these days and as much as I hate to lay blame the vendors selling them are at least partially responsible. I just bought 2 new distributor caps from Superformance and at least three of the wire bores were not deep enough to allow the screw-in pin to capture the lead, it would just pull right back out. I had to drill them a bit deeper, matching the measured depth of the original caps. Maybe not such a big hassle but you shouldn't have to do that on a brand new part.
     

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