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TDC Sensors

Discussion in '308/328' started by tobygaff, Jul 11, 2022.

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  1. tobygaff

    tobygaff Karting

    Dec 5, 2010
    196
    Fort Wayne, IN
    #1 tobygaff, Jul 11, 2022
    Good morning. I continue to fight issues with my car where the Digiplex units will not trigger the coils. The Digiplexes have been rebuilt, and the resistance on the TDC sensors seems to indicate they are ok. My question is this…. What do the sensors detect on the inside of the bell housing? I am assuming there is a pin or something on the flywheel. If so, is it possible for this pin to fall out? I am wondering if the sensors are ok, but maybe there is nothing for them to detect?

    Thanks for any help you can provide.
     
  2. s219

    s219 Formula Junior

    Aug 26, 2021
    484
    #2 s219, Jul 11, 2022
    There are small dowel pins pressed into the flywheel that serve as timing triggers. I have heard of the pins being destroyed by catastrophic clutch failure on other cars, so it's possible they can get damaged or fall out I suppose. But I doubt it would happen for no reason.

    I wonder if they are visible through the inspection window? They would be on the outer part of the flywheel, between the clutch and outer gear teeth.
     
  3. tobygaff

    tobygaff Karting

    Dec 5, 2010
    196
    Fort Wayne, IN
    #3 tobygaff, Jul 11, 2022
    Thanks. Is there more than one?
     
  4. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    26,640
    30°30'40" N 97°35'41" W (Texas)
    Full Name:
    Steve Magnusson
    #4 Steve Magnusson, Jul 11, 2022
    Just remove one of the sensors and look down the hole as you rotate the flywheel. There should be 2 pins 180 degrees apart that pass by.
     
    waymar likes this.
  5. ferrariowner

    ferrariowner Formula 3

    Feb 21, 2014
    1,148
    Mansfield, TX
    Full Name:
    Ron
    #5 ferrariowner, Jul 11, 2022
    Unlikely the pins are missing or damaged, although anything is possible. I seem to recall the sensors are very generic and can be purchased off of EBAY. Used on some VW models.
     
    waymar likes this.
  6. tobygaff

    tobygaff Karting

    Dec 5, 2010
    196
    Fort Wayne, IN
    #6 tobygaff, Jul 11, 2022
    Lol. I can barely get my hands to the sensors, there is no way I am getting my fat head in there!
     
  7. Cuddy K

    Cuddy K Karting

    Oct 30, 2017
    181
    Full Name:
    Ian Karr
    #7 Cuddy K, Jul 12, 2022
    replacing the one near the top of the engine just might be the hardest simple job ever.
     
  8. tobygaff

    tobygaff Karting

    Dec 5, 2010
    196
    Fort Wayne, IN
    #8 tobygaff, Jul 14, 2022
    Yeah, it does not look easy.
     
  9. Cuddy K

    Cuddy K Karting

    Oct 30, 2017
    181
    Full Name:
    Ian Karr
    #9 Cuddy K, Jul 14, 2022
    I used a crazy combination of wobble extensions and contortionist moves...and still it took me several multi-hour sessions to get it done ;)
     
  10. tobygaff

    tobygaff Karting

    Dec 5, 2010
    196
    Fort Wayne, IN
    #10 tobygaff, Aug 15, 2022
    It was not an easy job, however here are a few tips to make it easier.

    1. Working from underneath, you can get to it, however I also had some luck coming from the top. If you pull the rear distributor cap, there is some room to get in there.

    2. Tools. There a few tools that make this job much easier
    - 8mm magnetic socket
    -8mm magnetic deep well
    -1/4 inch drive wobble adapter
    - flexible socket extensions.
    Much easier than trying to control swivels.

    Here are the Amazon links if interested.

    https://a.co/d/h1Monm5

    https://a.co/d/hZAESrB

    https://a.co/d/hoJhsNl

    https://a.co/d/2duh2ZH

    I did not have one of these, but wish I would have:

    https://a.co/d/0V6MIym
     
  11. daynyc

    daynyc Karting
    Silver Subscribed

    Aug 5, 2016
    96
    #11 daynyc, Aug 15, 2022
    Proper resistance in a sensor does not assure that it is OK. I had a bad one and they all tested fine "on the bench." Are you 100% sure the boxes are well grounded?
     
  12. Baltz1969

    Baltz1969 Karting

    Apr 24, 2017
    74
    Chula Vista, CA
    Full Name:
    Jose Baltz
    #12 Baltz1969, Aug 15, 2022
    Hi this might sound stupid, is it possible the crank sensors for the 1/4 cylinders & the 5/8 cylinders are crossed? On my 81 the 1/4 wire is yellow & the 5/8 is green, wouldn't hurt just to double ck them. If you already confirmed they r connected correctly, disregard this message. Good luck


    Sent from my iPad using FerrariChat.com mobile app
     
  13. mwr4440

    mwr4440 Five Time F1 World Champ
    Rossa Subscribed

    Jun 8, 2007
    57,863
    Bavaria, The 'Other' Germany
    Full Name:
    Mark W.R.
    #13 mwr4440, Aug 18, 2022
    Are we talking about the MM SEN8s?
     

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