No power at Cold Start Injector or Thermal Time Switch | FerrariChat

No power at Cold Start Injector or Thermal Time Switch

Discussion in '308/328' started by swazzy, Jun 29, 2025.

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  1. swazzy

    swazzy Rookie

    Jan 15, 2021
    16
    CT
    #1 swazzy, Jun 29, 2025
    Last edited: Jun 29, 2025
    I'm investigating why there is no power to the CSI or TTS on my 1984 308 QV USA. One item I discovered and want to eliminate as a possible reason is the orientation of the O2 diode in the ECU. I've attached a number of photos. For reference the wiring diagram is from a special set for US 1984-85, which shows the diode, and which gets its power from the Start Valve relay (not shown in the diagram). Power comes from the start valve relay to the singe wire on the right of the diode. Then it supposed to pass through the diode to go to the TTS (107 in the diagram). The orientation of the relay as I discovered it is image A. But that seems counterintuitive because it seems the diode would not allow power to pass in that direction (which I confirmed with a bench test) and only to flow in the other direction (from the generator 59, to the battery 51). So it would seem like the diode should be flipped, but I want to confirm. The rough diode drawing in each image is oriented the same as in the diagram just for reference. My question is; Is diode orientation A correct ,or is orientation B correct?

    Maybe I'm not reading any of this correctly and I would certainly appreciate any input from the members.

    Thank you all.

    Marc
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  2. rwbolt1

    rwbolt1 Karting

    Sep 10, 2006
    213
    Boerne, TX
    Full Name:
    Rodney Bolt
    Did you purchase the car with this condition (no power to CIS & TTS) or did they just stop working?
     
  3. swazzy

    swazzy Rookie

    Jan 15, 2021
    16
    CT
    I've had the car for about 3 years and I don't think its ever been working. It always takes a number of cranks to get it started when cold. But starts up on the first crank when warm. I finally decided to investigate the CSI and first put the injector in a cup, and no fuel came out. To check if the injector itself was faulty I put power directly to the CSI and fuel pump and then injector then sprays fine. Then started checking power and none gets to the CSI or TTS. I am getting power to the start valve relay, and all the way to that diode. I just don't want to flip that diode without some guidance because I don't want to do anything that might damage other components in the ECU...
     
  4. rwbolt1

    rwbolt1 Karting

    Sep 10, 2006
    213
    Boerne, TX
    Full Name:
    Rodney Bolt
    #4 rwbolt1, Jun 30, 2025
    Last edited: Jun 30, 2025
    Here's what Grok says based on the picture of the diode you provided:

    "The diode has labels "59 Generator" on one side and "51 Battery" on the other. Typically, in automotive or electrical diodes, the positive (+) side is associated with the generator (or power source) and the negative (-) side with the battery (or load). Based on this convention, the "59 Generator" side is likely the positive (+) side, and the "51 Battery" side is likely the negative (-) side."

    With that explanation, your "B" pic is the correct orientation. (Arrow (+) pointing to the vertical line (-) in a diode electrical schematic.)
     
  5. swazzy

    swazzy Rookie

    Jan 15, 2021
    16
    CT
    I'll take that as confirmation and test it. Thank you for looking that up.
     

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