Can you help to troubleshoot this issue...? | FerrariChat
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Can you help to troubleshoot this issue...?

Discussion in '456/550/575' started by belfry, Sep 20, 2024.

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  1. belfry

    belfry Formula Junior

    May 14, 2015
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    Robert Batt
    #1 belfry, Sep 20, 2024
    My 1995 456 GT 6 speed with 60,000 miles has started to act up a little.

    Initially, I noticed that it would 'bog down' when I tried to raise the rpm when it was cold. It would start fine but not feel very willing to rev.

    For the first 60 seconds of driving the car would splutter and backfire slightly. This seemed to clear after a couple of minutes.

    Driving the car today, I noticed the reluctance to rev, but there was not backfiring. The car did feel slightly hesitant at around 2,500 rpm in third, but it would pull strongly.

    I decided to try an Italian Tune Up, and red lined the car several times in 1st, 2nd and 3rd gears :). It pulled strongly in all these gears, but then the red Slow Down 7-12 light blinked a couple of times. It went away when I did slow down. I added a bottle of injector cleaner without any improvement.

    Any initial thoughts?
     
  2. fatbillybob

    fatbillybob Two Time F1 World Champ
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    #2 fatbillybob, Sep 20, 2024
    one bank sounds down.
     
  3. 12659

    12659 Formula Junior

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    #3 12659, Sep 20, 2024
    Check fuel pressure.
     
  4. Qavion

    Qavion F1 World Champ
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    #4 Qavion, Sep 20, 2024
    Fuel regulation issue? Intermittent sparking? How hard is it to swap coil packs on 456’s?

    I guess if the issue hasn’t been going on for a long time, a spark plug inspection might not show any abnormalities?

    Is your car a 2.7 or 5.2? How hard is it to pull engine codes or get fuel/air ration readings?
     
  5. dcanderson51

    dcanderson51 Rookie

    Jan 29, 2022
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    #5 dcanderson51, Sep 20, 2024
    Similar issues on my 550 traced to fuel pumps.
     
  6. belfry

    belfry Formula Junior

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    #6 belfry, Sep 21, 2024
    Thank everyone for your thoughts.
    There is what seems like equal pressure from the exhausts on either side.
    I will order a fuel pressure gauge
    No coil pacts on a 456 to swap
    I will check the plugs for condition
    the car is a UK 2.7 Motronic so no OBD

    I made the assumption that the Slow Down light will have been caused by too much (unburnt) fuel reaching the cat on that side. Would a failing fuel pump cause this issue?
    Would the 'bogging down' and unwillingness to rev indicate too little or too much fuel?
     
  7. Qavion

    Qavion F1 World Champ
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    #7 Qavion, Sep 21, 2024
    You mean they are too hard to get to? See #8.

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    Maybe I'm calling them the wrong thing. Then there is also #1 to swap.... Ignition control modules/ignition power modules.

    Crank sensors can also cause these kinds of issues.
     
  8. Qavion

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    #8 Qavion, Sep 21, 2024
    Failure of proper combustion. Can be caused by too little fuel, too much fuel, no spark, improper timing, etc.
     
  9. belfry

    belfry Formula Junior

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    #9 belfry, Sep 21, 2024
    Apologies, I was thinking about the individual coil pacts that attach to the spark plugs on 'modern' cars!

    Is there an easier way to tell which bank is suffering without having to do another Italian Tune-up once I have swapped the coils over? If I swap these and can trigger a slow down 1-6 light then that would be helpful but it doesn't feel very mechanically 'kind' to the car.
     
  10. belfry

    belfry Formula Junior

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    #10 belfry, Sep 21, 2024
    I have a device that sits on the spark plug wire and indicates when the plug is sparking. I have checked and all plugs are firing and sparking.
     
  11. Qavion

    Qavion F1 World Champ
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    #11 Qavion, Sep 21, 2024
    Sounds good, although driving the car can put extra stresses on the systems. Vibration, heat, etc. I guess it's your choice what to do next... Swap components for further evaluation, check fuel pressure, look over the engine for loose connections, etc.
     
  12. Alex550M

    Alex550M Rookie

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    #12 Alex550M, Sep 21, 2024
    did you check the fuse board and relays ? maybe there is a faulty one
    I had similar issue, noticed a damaged connector, overheating fuse board and the cause was the relay that is under the steering column !
     
  13. carguy246

    carguy246 Formula 3
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    #13 carguy246, Sep 22, 2024
    Is it possible that you disconnected the battery and restarted the car without going through the relearn procedure? In any event, you could disconnect the battery and then do the relearn procedure in the morning. This might help but it would erase any stored codes which might be helpful in diagnosis. Just a suggestion, good luck.
     
  14. Qavion

    Qavion F1 World Champ
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    #14 Qavion, Sep 22, 2024
    There's a relay under the steering column on 456GT's? Do you know what it does?
     
  15. Alex550M

    Alex550M Rookie

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    #15 Alex550M, Sep 24, 2024
    not sure 100 percent, but it's the link between the key's related input and the main fuse board. For instance, without it, the car won't start. With a faulty one like mine which was on-off all the time, it created overheat in the fuse board. A "little b*stard" to monitor if you want my opinion ;)
     
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  16. Qavion

    Qavion F1 World Champ
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    #16 Qavion, Sep 24, 2024
    I know the 5.2 cars have a start relay, but I have no idea where it lives. On earlier cars, some folks may have installed aftermarket immobilisers with start relays.
     
  17. scowman

    scowman F1 Rookie

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    #17 scowman, Sep 25, 2024
    This is not hard and the coil packs are known to fry next to the exhaust manifold without looking bad externally. One of the great things about the dual management systems of the Ferrari is to swap parts and see if your problem switches sides.
     
  18. belfry

    belfry Formula Junior

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    #18 belfry, Sep 27, 2024
    I am now back at home. The fuel pressure gauge kit was waiting for me.

    I attach a diagram of the fuel supply bits on 014 Injection Device
    I have not tested fuel pressure before. I am primarily looking to see whether the fuel pumps are both working normally.

    There appear to be Schraeder valves on the end of each Injector Tubes (number 6 on the diagram). Do I attach the kit to these valves to check the pressure?
    Apologies for my inexperience!
     

    Attached Files:

  19. belfry

    belfry Formula Junior

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    #19 belfry, Sep 27, 2024
    And what would be considered 'normal' ranges for the fuel pressure?
     
  20. Qavion

    Qavion F1 World Champ
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    #20 Qavion, Sep 27, 2024
    Correct.

    Here's the procedure in the WSM, but it involves the use of a vacuum pump for the last step.

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    Also, there is a complicated procedure for testing pump efficiency.

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  21. belfry

    belfry Formula Junior

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    #21 belfry, Sep 28, 2024
    Thank you Ian. This is very kind of you. I will report back.
     
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  22. Alex550M

    Alex550M Rookie

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    #22 Alex550M, Sep 28, 2024
    left side, below the air vent on a 550. it is visible. I enclose a picture to figure it out. I believe that it is the same for a the 550 is an evolution of the 456

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  23. Qavion

    Qavion F1 World Champ
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    #23 Qavion, Sep 28, 2024
    The 550 parts manual does show a relay somewhere on the left hand side (#13), but doesn't say what its purpose is.

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    As the start relay is controlled by the immobiliser, I'm not sure it would be fitted to early 456GTs.

    The 456GT only has hazard/turn components on the left hand side (according to the parts manual).

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    The 456M and, I assume the 456GT with the 5.2 engine may have a start relay, but it's hard to identify.

    #36?

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  24. belfry

    belfry Formula Junior

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    #24 belfry, Sep 29, 2024
    Update.

    The fuel pressure on both fuel rails is 3.4 bar with the engine idling.
    The fuel pressure remains around 3.0 bar with the engine stopped.
     
  25. Qavion

    Qavion F1 World Champ
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    #25 Qavion, Sep 29, 2024
    Sounds perfect, but I suppose this does not completely exclude the fuel supply or injector system. It might struggle at higher rpms. This is when I call in the experts :p I don't like messing with open fuel lines. Not sure where to go from here. It could be anything.
     
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