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Loss of tach and Eng power 328GTS, one timer!

Discussion in 'Technical Q&A' started by Nationaltec, Feb 5, 2004.

  1. Nationaltec

    Nationaltec Karting

    Dec 22, 2003
    157
    North County
    Full Name:
    Patrick
    Guys,

    Strange & almost dangerous thing happened to me today.

    I pulled out of a restaurant (engine started as normal) then as I'm crossing the intersection and I notice "I have no TACH" and my throttle has almost no effect.

    I just made it thru the intersection but I didn't have enough power to climb the pending hill.. Thus I pull over.. Turn the car off an restart as normal..!! No more problem... (drove tonight about 30 miles, worked just fine)

    No strange sounds, nothing ? I didn't realize the power loss until I attempted to accelerate.

    Did I loose half a bank? Coil?

    Where does the Tach get it's signal?

    Appreciate any input ...
    Scary place for it to happen!
    Patrick
     
  2. Chiaro_Slag

    Chiaro_Slag F1 Veteran

    Oct 31, 2003
    7,731
    CA
    Full Name:
    Jerry
  3. Philjay50

    Philjay50 Formula Junior

    Jan 16, 2003
    587
    Chester, England
    Full Name:
    Philip
    I do not know if the system is the same, but on my 84 Mondial there are two ignition modules and two coils. I had the same problem, and discovered that only one module sends the signal to the tacho (front bank in the case of the Mondial, not much help to you). The problem showed itself as the car losing one bank of cylinders and the tacho not working , although you could still have the power loss and the tacho still work if it was the other module.
    I traced the problem, after much head scatching to the flywheel /ignition sensors, there are three on the Mondial, one for each cylinder bank (and therefore one for each ignition module) and a TDC sensor.
    If the set up is the same, I would check these sensors first.
    The replacement is the same as a Lancia or Fiat sensor by the way.

    Hope this helps.
     
  4. 308GTS

    308GTS Formula 3

    Dec 27, 2001
    2,220
    TN
    I believe there are 2 TDC sensors and one RPM sensor for the tach. It could be this sensor that is going or your coil.
     
  5. Chiaro_Slag

    Chiaro_Slag F1 Veteran

    Oct 31, 2003
    7,731
    CA
    Full Name:
    Jerry
    It wouldn't be the throttle cable you had replaced would it?
     
  6. BigTex

    BigTex Seven Time F1 World Champ
    Rossa Subscribed Owner

    Dec 6, 2002
    73,162
    Houston, Texas
    Full Name:
    Bubba
    Hey Patrick!

    I've had the EXACT same scenario with my '77 308GTB last week.

    Mine has been an intermittant problem for the past six months, but finally went bad over the weekend.

    Will report back on what my tech finds. Thanks also for the clue on the flywheel sensor.
     
  7. BigTex

    BigTex Seven Time F1 World Champ
    Rossa Subscribed Owner

    Dec 6, 2002
    73,162
    Houston, Texas
    Full Name:
    Bubba
    My tech didn't think it was the coil, due to the fact my engine would "come back on" for many months, with only a momentary dip in power.

    I suspect bad wiring, or maybe the tach itself shorting to ground via wiring loom.
     
  8. Verell

    Verell F1 Veteran
    Consultant Owner

    May 5, 2001
    6,992
    Groton, MA
    Full Name:
    Verell Boaen
    It can be almost anything that will cause ignition failure of the bank that generates the tach signal. ie:
    - Sensors (as descr below)
    - wiring & connectors
    - ECU for that bank.

    Less likely to be the coil than something earlier in the signal train.

    Intermittent elec. gremilins ain't no fun...
     
  9. f355spider

    f355spider F1 World Champ
    Rossa Subscribed Owner

    May 29, 2001
    17,059
    USA
    Full Name:
    Hugh G. Rection
    A 77 308 and a 328 have very different ignition systems....
     
  10. Nationaltec

    Nationaltec Karting

    Dec 22, 2003
    157
    North County
    Full Name:
    Patrick
    Thanks Speed, let me know what your tech finds. I'm dropping mine off for major service on Thur in conjunction with my Ireland vacation. (So they will have plenty of time to go over everything)

    I'll let you know what they find when I return.


    I agree with Verell, I'm leaning towards a wire issue or contact resistance.

    I've read about problem coils on 328's but wouldn't they just competely fail? Nothing intermittent about a coil as far as I know?

    We'll see !!

    Thanks for the input guys...
    Patrick



    *no on the t-cable Slag, that's ok...
     
  11. davehelms

    davehelms F1 Rookie

    Jan 3, 2004
    4,629
    Full Name:
    Dave Helms
    Look at the harness plug in the top of the left rear wheel well. When the problem involves a tach and coil drop out problem, this is the most likly problem spot.
     

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