TR question - possible Thermo Switch issue | FerrariChat

TR question - possible Thermo Switch issue

Discussion in 'Boxers/TR/M' started by 90TR, Nov 8, 2012.

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  1. 90TR

    90TR Formula Junior

    Nov 23, 2005
    274
    Celebration, FL
    Full Name:
    Bill
    Hi everyone,

    My 1990 TR is generally the most reliable of my vehicles, so I was caught off when last night I started her to come home from work and the engine did not feel right. I also noticed my Tach was barely moving when I stepped on the gas. I nursed her home and started the checks listed in multiple posts. First I ran a jumper on the fuel pumps at the relays and both hummed. I then pulled the air cleaner and both air plates seemed OK. I then restarted her and she was running a little better, but not as good as normal. I then started checking wire connections at the ECU and so on to check for anything obvious. When I touched the two wires at the water neck at the top back of the engine, the car stalled and would not restart. I am guessing a wiring issue/bad connection, and will look at these this evening. From what I read these would impact the ECU and running, but why would the tach be having issues?

    http://www.ricambiamerica.com/parts_catalogs.php?M=FE&P=&V=diag&I=2851

    #'s 19 and 21 are the connectors I think these are.

    Any warnings or things to watch out for before I start pulling these apart?

    Thanks,
    Bill
     
  2. tf308

    tf308 Formula 3

    Dec 14, 2003
    1,168
    Virginia Beach
    Full Name:
    Tim
    I think #19 goes to your water temp guage (that you read in the cabin)

    not sure about #21...but that may tell the ecu what temp the water is so that it can properly meter the fuel...


    My guess is that #19 will not affect how your car runs, but #21 will.
     
  3. turbo-joe

    turbo-joe F1 Veteran

    Apr 6, 2008
    8,868
    southwest germany and thailand
    Full Name:
    romano schwabel
    the switch with only 1 contact is for the gauge inside, this with 2 contacts for the injection
     
  4. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    25,041
    30°30'40" N 97°35'41" W (Texas)
    Full Name:
    Steve Magnusson
    #4 Steve Magnusson, Nov 9, 2012
    Last edited: Nov 9, 2012
    That is definitely a bad sign. Here's a description of the various items on the "Y" water neck (so we can be clear about names):

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    Here's how to measure the resistances of each part of the 2-Channel Thermistor at the (unplugged) injection ECU connectors. When making the measurement, give the connector on the 2-Channel Thermistor a little wiggle to make sure the value doesn't change significantly:

    Image Unavailable, Please Login

    Yes, seems unrelated. Are you sure that spark is good on both banks?

    Also, please confirm this is a US version TR.
     
  5. 90TR

    90TR Formula Junior

    Nov 23, 2005
    274
    Celebration, FL
    Full Name:
    Bill
    Thanks again for all the knowledge. As I said I am extremely spoiled with this car as it has been very consistent and reliable over my now 7 years of ownership.

    My car is a US spec 1990. I tried the tests and everything seemed OK. So I cleaned the connecters for the Thermo-Time Switch and 2 Channel Thermistor, used a dental pick to tighten the prongs, and added some grease. They did not seem particularly dirty, but they are on top of the engine so it may have been a water issue. Anyway, I am not sure if I did something during the tests or when I cleaned the connectors, but she is running great now. I do however still have the problem with the tach. So I am working with the theory I had two separate issue pop at the same time.

    I am just going to admit I am lost on how the Tach in this works. Currently the tach at idle is resting on the pin. If I hit the gas, the tach moves, but it is slow and not fully reflecting the true RPM. This falls right in between my experience. Not old enough to be distributor only and not new enough to plug it in and read the code. Would someone run me through how this system works and some possible tests to see if I can ID the cause?

    Thanks again, Bill
     
  6. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    25,041
    30°30'40" N 97°35'41" W (Texas)
    Full Name:
    Steve Magnusson
    Unfortunately, there's nothing in the F documentation giving any real details. The MicroPlex ignition ECU receives input signals from the flywheel sensors and then (internally) generates the (separate) signals to fire the power modules/coils and run the tach. All you can deduce from your symptom is that either the MicroPlex ECU is bad (more unlikely IMO) or the tach itself has a problem (more likely IMO as TR/328 Owners have more often reported a problem with the Tach itself than with the MicroPlex ECU).
     
  7. Jeff Pintler

    Jeff Pintler Formula Junior

    Jul 20, 2005
    537
    Richland
    Full Name:
    Jeff Pintler
    I seem to remember something from the old ferrarilist days: when one of the water sensors fail, half the engine cuts out. The shop that worked on the car replaced the caps, rotors and wires, then the 'ecu' then finally the sensor. Had a similar problem with mine and cured it by replacing the sensor. FWIW.

    Jeff Pintler
    89 348tb, 86tr, 99 360 3-pedal
     
  8. Jeff Pintler

    Jeff Pintler Formula Junior

    Jul 20, 2005
    537
    Richland
    Full Name:
    Jeff Pintler
    Oh yeah, sometimes an intermittant problem will test good and be bad.


    Jeff Pintler
     

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