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355 Slow down light diagnosis and test to repair?

Discussion in '348/355' started by 355OXO, Feb 16, 2020.

  1. emac

    emac Formula Junior
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    Sep 14, 2014
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    upstate SC
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    ernest
    as I recall mine didnt. just when it warmed up. I think the bypass and cat have different set off values. Easy enough to check, the connectors are behind the back right wheel.
     
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  2. Qavion

    Qavion F1 Rookie

    Feb 20, 2015
    3,096
    Sydney
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    Ian Riddell
    I recall the same thing, that's why I don't think it's swapped plugs. But, as you say, it's relatively easy to check.
     
  3. drbob101

    drbob101 F1 Rookie
    Silver Subscribed Owner

    Nov 26, 2012
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    Bob Ferraris
    The values from the right cat and from the bypass location will be very different. At start up /cold they would both be .5v and on operation would be different.

    We don’t know exactly what the Ecu is looking for from the bypass TC or what triggers a SDL from that. I have seen it trigger with a faulty TC that was throwing voltage spikes intermittently.

    So my answer would be possibly if the switched component is faulty but if all parts are operational then at ignition I would say no.
     
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  4. 355OXO

    355OXO Karting

    Apr 16, 2006
    98
    UK
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    Simon
    Hi Guys,
    Thanks for all the input. I have now undertaken the tests from the thread from DROCK 28 to test my ECU with the Thermocouple connected. I have identified that one of my thermocouple units is at fault. I am going to try an experiment I have purchased to K type thermocouple from eBay that I intend to try on my car as these were only $25 for 2. I need to change the connectors to the ECU to fit. I will let you know how I get on with this low cost mod.
     
  5. malex

    malex Formula 3
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    Dec 5, 2007
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    Mark
    That's exactly what I did Simon. Only in my case, my thermocouples checked out but the exhaust bypass CCU was bad. I used a generic K-type thermocouple (0-1250 deg C, adjustable length) as a baseline, then observed cold vs hot voltage changes on my multi-meter. To make the thermocouple connection easier, and to experiment down the road with finding another solution to the CCU, I also bought a set of cheap connectors on Amazon as well, https://www.amazon.com/gp/product/B07KP369MF/ref=ppx_yo_dt_b_asin_image_o00_s02?ie=UTF8&psc=1

    If your thermocouple solution works, please post the source. The K-type that I bought has adjustable length and an "L" bend but has a 1/8" NPT fitting rather than the correct metric fitting, plus it's 5mm dia for the entire length and doesn't step down to 3mm as does oem.
     
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  6. 355OXO

    355OXO Karting

    Apr 16, 2006
    98
    UK
    Full Name:
    Simon
    This sounds very similar, my Thermocouple are adjustable for length too and do not step down either, i don,t think this matters. Beats paying Ferrari price.
     
  7. malex

    malex Formula 3
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    Dec 5, 2007
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    Mark
    Simon, do you have a link for the source that you used? I can only find the thermocouple that I'm looking for with NPT fitting. Do you know if M8 is correct fitting size? Regardless, I might be able to reuse the nut from a failed thermocouple when needed.

    Agreed that it pays beating Ferrari prices. I know that Technistrada sells them for $30 but he hasn't had them in stock for a while.
     
  8. 355OXO

    355OXO Karting

    Apr 16, 2006
    98
    UK
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    Simon
    That is why i went on EBAY as Technistrada was out of stock. The UK EBAY I.D. is 163898613905. I may have to change the fitting from my old Thermocouple.
     
  9. malex

    malex Formula 3
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    Dec 5, 2007
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    Mark
    Thanks. We found the same thermocouple. Yours has the same 1/8" NPT fitting per the eBay listing.
     
  10. 355OXO

    355OXO Karting

    Apr 16, 2006
    98
    UK
    Full Name:
    Simon
    I have now received the eBay thermocouple X 2. I have removed the original fittings and compared these with the fittings that come with the thermocouple and they appear to be the same. I think the trick is to work out where you want the olive on the shaft of the thermocouple and clamp this in place by compressing the joint with the fittings supplied. Then remove the fittings and use the threaded cap nut Supplied that has the same thread as my bypass pipes. I will fit these hopefully tomorrow and let you know how I get on.
     
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