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Car won't start

Discussion in '456/550/575' started by Rodgerrr, Jun 18, 2023.

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  1. Rodgerrr

    Rodgerrr Rookie

    Apr 26, 2013
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    #26 Rodgerrr, Oct 6, 2023
    Qavion, I've been meaning to thank you for those circuit diagrams - they are super and a lot easier to follow than those is the WSM - and likely a lot more correct. With regard to the output from the fuel level sensor: I traced it into and out of the Digtek displau unit and then, from there, to the fuel gauge. I could not find where it went to the ECU connector, 277. Would please double check that and see if I've missed something. thx
     
  2. Qavion

    Qavion F1 World Champ
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    #27 Qavion, Oct 6, 2023
    Last edited: Oct 6, 2023
    Ooops... my mistake. I think I got my wires crossed.

    Those instrument panel plugs are a nightmare. There are numerous wire colour changes on different sides of the plugs. There isn't a diagram showing these plugs in the 550 manual, so I use the 456M diagrams.

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    Anyway, after further reading, I believe the fuel quantity low signal goes to pin 42 of the RH ECU. Follow the purple/yellow (ZG) wire to connector 277 (pin 3) in my diagrams.

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    This goes to Digitek plug/pin C4.

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    There are a lot of weird labelling issues in the WSM diagrams and in the WSM itself adding to the confusion. Here are some of them:
    The WSM Digitek Unit pinout had the plugs mislabelled. They labelled 20 pins on a 16 pin plug. I used my own labelling to resolve the issue. See image above.
    The footwell fuses were labelled back to front in the wiring diagrams (compared to the Owners Manual).
    The L/H Motronics wiring diagrams seemed to be labelled back to front (Left instead of Right).
    The Motronic ECU pin numbering was one pin offset in the wiring diagrams.

    I'm not sure what signal is being sent from the Digitek unit to the Motronic ECU, but I suspect it's just an earth when the fuel is low.

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  3. Rodgerrr

    Rodgerrr Rookie

    Apr 26, 2013
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    #28 Rodgerrr, Oct 22, 2023
    I just got back to working on this. I did what you suggested and put a 100 0hm resistor across the fuel sensor connector - fuel gauge immediately read half full. The car would still not start - however. Right now the resistance across the sensor output pins is 220 ohms - it has a little over 1/4 tank so there is something going on there i don't understand (maybe a bad connection at the sensor? it seems that an open would be seen as an empty tank) I I went to start unplugging the right side ecu connector to see if I could find anything there and ran into a problem. I can't seem to get the connector off. I lifted the clamp and uncrewed the retaining screw on the bottom. The top of the connector will tilt back to the extent that the connected wires will let it but it seems to be hinged to something on the bottom. Is there a trick here I am not aware of?
     
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  4. Qavion

    Qavion F1 World Champ
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    #29 Qavion, Oct 22, 2023
    Pity... I guess we can cancel that theory.

    Yes, it's kind of hinged. It's actually a hook. I guess that's to ensure lateral alignment, but it always gives me the impression that it is mating the pins at an angle. You may have to remove the ECU to get more freedom of movement.

    I wonder if the geometry is different to other Ferrari fuel senders. It could be that higher resistance = lower quantity. Sorry, no experience with 550 fuel senders.
     
  5. Qavion

    Qavion F1 World Champ
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    #30 Qavion, Oct 22, 2023
    Last edited: Oct 22, 2023
    Can you recall which way up the fuel sender plug is mounted? I assume it's something like this:

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    Or is that upside down?

    Does yours have an "N" marking? If so, is it at 12 o'clock, 1 o'clock, etc...

    (sorry for the digression)

    (EDIT: I'm not sure if that is an OEM sender in the photo. I think MARWAL may be an English brand)
     
  6. Rodgerrr

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    #31 Rodgerrr, Oct 22, 2023
    Image Unavailable, Please Login This is a pic of level sensor - up in the image is up. The mating connector is in the foreground with a 100 ohm resistor inserted. I've never pulled that sensor since I've had the car.
     
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  7. Qavion

    Qavion F1 World Champ
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    #32 Qavion, Oct 22, 2023
    Last edited: Oct 22, 2023
    Thanks. So it looks like it is orientated 180 degrees to my previous photo.

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    Unfortunately, I can't read the increments. Also, it's a 3 pin connector, which means it could be wired in two ways to suit the car.
     
  8. Qavion

    Qavion F1 World Champ
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    #33 Qavion, Oct 23, 2023
    So... at this point, we haven't run out of possible causes... We are just lacking the technical abilities to carry on with faultfinding.

    e.g.

    We don't know what information the Immo is looking for. It certainly has enough info to crank the engine (something controlled by the Immo ECU). It just doesn't seem to want to allow the Motronic ECUs to activate the fuel injectors.

    We also have these confusing messages regarding the inertia switch. Maybe you could ask Leonard tech the difference between these two messages?

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    What does "OFF" mean?

    Since there is no direct wiring between the inertia switch and the Motronic ECUs (like the F360, for example), perhaps the signal goes via the instrument panel to the ECUs?



    By the way, with the fuel tank sender plug disconnected, did you check the fuel quantity? Does open circuit (high resistance) = high or low fuel quantity?
     
  9. Rodgerrr

    Rodgerrr Rookie

    Apr 26, 2013
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    #34 Rodgerrr, Jan 2, 2024
    Qavon, if you are ever in Tucson - dinner and drinks are on me. I had to find the time and an available friend before I could sort my car out - it is now running. The problem was in the line you traced out in one of the schematics you sent me which is the signal I/f between the immobilizer and the right side engine ECU. There is an in-line 21 pin connector right above the ECU where the wire going to pin 88 of the ecu connector had an issue. The connector was fine. The problem was that the wire was not crimped correctly and was not making electrical contact with the back side of the connector socket. As I was moving the wire it came right out leaving a piece of crimped insulation. So, lacking a pin/socket extraction tool, we wired around that connector and the engine fired right up. My friend, a corvette fanatic, was not impressed with what he saw re Ferrari electronics expertise.
     
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  10. Qavion

    Qavion F1 World Champ
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    #35 Qavion, Jan 2, 2024
    Wow... good find. Thanks for the follow up!
     
  11. Qavion

    Qavion F1 World Champ
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    #36 Qavion, Jan 2, 2024
    So, for my reference, a problem with pin 20 wiring on connector 277

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    Pin 20 goes to the Immo Interface box (the one with all the mysterious black wires on it) on one side of plug 277. For clarity (in my diagrams), I've shown the wire in pink, because the wire changes to pink on the Motronic ECU side of connector 277. i.e. there is a pink wire going to pin 88.
     
  12. Rodgerrr

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    Apr 26, 2013
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    #37 Rodgerrr, Jan 4, 2024
    I believe all that is correct - traveling right now am away from my home computer - I’ll confirm when I get home - this weekend.
     
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  13. Rodgerrr

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    Apr 26, 2013
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    #38 Rodgerrr, Jan 15, 2024
    Qavion - yes that wire was the problem. Car runs great now. Thanks again. The only thing I wish I done while apart was sort out the fuel level indication. When full - the guage is showing 3/4 full and when about 1/3 full the guage is showing empty. I'll probably live with it until/if I need to pull the fuel pumps again.
     
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