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456 power loss and oil thrown out - any guesses? Plus Ferrari specialists in Spain

Discussion in '456/550/575' started by Granada456, Feb 19, 2021.

  1. Granada456

    Granada456 Karting

    Dec 8, 2020
    62
    Granada
    Full Name:
    Julyan
    Thanks for the info. Yes, I think I should move towards the 21st century and get familiar with on-board diagnostics now that I'm running two 90s cars with electronic fuel injection as classics.
     
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  3. fatbillybob

    fatbillybob Two Time F1 World Champ
    Consultant Owner

    Aug 10, 2002
    20,360
    socal
    Never heard that one before....and don't get how it can contaminate the crankcase with fuel.
     
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  4. asgor

    asgor Formula Junior
    Silver Subscribed

    Sep 8, 2016
    509
    Virginia, USA
    I thought it was just me... but I don't get it either. Maybe I am just not fully understanding how the FPR operates but how in the world would a failed FPR diaphragm/ broken FPR inject oil into the crankcase?
     
  5. Robbe

    Robbe Formula Junior
    Silver Subscribed

    Aug 22, 2013
    579
    The Netherlands
    It would not directly inject fuel into the crankcase of course, but when the pressure of the fuel system gets too high (failing FPR, maybe blocking the dump into the return line), the injectors will inject too much fuel into the cilinders.
    In theory this can be so much, that the fuel does not ignite, and drip down the walls, past the rings and into the crankcase.

    But only on one bank. A camera can check if the broken-FPR -bank has cleaner cilinders and plugs, as the raw fuel must have cleaned them a bit, compared to the good bank.
    But I would certainly look into the oil pressure valve.
     
  6. brogenville

    brogenville Formula Junior
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    Apr 24, 2012
    951
    UK
    Full Name:
    Robin
    I would have thought you would be getting much more serious problems than fuel in the oil if you’re getting to the point of hydraulically locking the cylinders full of fuel.


    Sent from my iPhone using FerrariChat
     
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  8. Granada456

    Granada456 Karting

    Dec 8, 2020
    62
    Granada
    Full Name:
    Julyan
    What I imagined was that if the regulator diaphragm had ruptured, extra fuel would get into the inlet manifold, where it would be in bulk liquid form, rather than as an aerosol, and so would end up as described above, going down the cylinder walls into the oil.
     
  9. Robbe

    Robbe Formula Junior
    Silver Subscribed

    Aug 22, 2013
    579
    The Netherlands
    When doing a compression test of an engine, if a cylinder has less pressure, a next step is inserting a teaspoon full of oil into that cylinder through the plughole, and test again. When the test now gives a higher compression, the rings have play which the oil temporarly has filled up.
    This suggests that oil normally seals , or is part of the sealing system of the rings.
    Excess fuel diludes and washes away that oil, and creating a leak for the fuel to pass.
    See the fuel as a penetrating fluid, opening up the acces to the crankcase underneath the pistons.

    As the fuel pressure only exists with the engine running, the injectors can only inject too much with the engine running.(when shut down, the remaining fuel pressure is not enough to fill the combustion rooms)
    And that means that the excess raw fuel is not only going past the rings, but also past the opening exhaust valves , which by the way is bad for the cats.

    Hydraulocking with fuel therefore is not likely. With water/coolant this is much more of a danger, as that does not dilude and wash away the oil, and then the fluid is trapped more.

    In my opinion, and I am not a mechanic, if the O2 sensors (especially the post cat ones) are behaving normally now, no real harm is done to the cats.
    And if the long term fuel trim value is ok, more or less the same as the other bank, I would not worry about this. It is a 20-25 year old car, and sensors and check valves etc do get older and sometimes are at the end of their lifespan.
     
  10. Granada456

    Granada456 Karting

    Dec 8, 2020
    62
    Granada
    Full Name:
    Julyan
    Mine's a 1994 car, so 27 years old now, in fact. Yes, I completely agree with you, Robbe; that is my thinking too. I'm waiting to hear from the mechanic the results of his various checks, and will update this thread when I get them.
     
  11. Granada456

    Granada456 Karting

    Dec 8, 2020
    62
    Granada
    Full Name:
    Julyan
    The compressions have now been checked and are somewhat low on the bank that suffered the fuel wash. The mechanic is recommending that we try first, before thinking of opening up the engine, to run the engine as is, once the fuel pressure regulators have been fixed, and see whether the rings might bed back in in those cylinders. He is thinking to try some oil additive that is supposed to aid the ring seating process.
     
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  13. franschman

    franschman Karting

    Dec 18, 2017
    220
    Holland
    Full Name:
    Bart
    #35 franschman, Mar 16, 2021
    Last edited: Mar 16, 2021
    Sound advice
     
  14. Davidspop

    Davidspop Karting

    Dec 23, 2019
    205
    Full Name:
    Lance Malcolm
    So what was the outcome? I hope all reformed back to cylinders.....
     
  15. Granada456

    Granada456 Karting

    Dec 8, 2020
    62
    Granada
    Full Name:
    Julyan
    I haven't given you an update because there isn't one to give, yet. The car remains with the mechanic in Madrid, who has been waiting for replacement fuel pressure regulators to arrive. These may have arrived by now; I haven't spoken to him this week yet. There also remains the problem I had with engaging some gears after running for a while. The mechanic is going to look into that issue too once the car is running again. He has told me that from my description he thinks that it might be a simple thing, or might indicate some deeper problem within the gearbox. I need to go to Madrid (about 400 km from me) for other business in the next few days, and I'll try to schedule things to go and see the mechanic to find out more then, and will let you know. Meanwhile Bart, franschman from this forum, put me on to a replacement window ECU at a good price, which I have bought over Ebay and is coming from Modena. Thanks, Bart! So at least I'll be able to fix that issue once the mechanical issues have been sorted. This window issue is of course minor compared to the mechanical questions, but I would not be able to pass annual vehicle inspection here with a car where one of the windows doesn't go up and down.
     

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