Ferrari 412. Uneven banks. Trying to diagnose the problem. | FerrariChat

Ferrari 412. Uneven banks. Trying to diagnose the problem.

Discussion in '365 GT4 2+2/400/412' started by 360modena2003, Apr 8, 2023.

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  1. 360modena2003

    360modena2003 Formula 3

    Jul 11, 2009
    2,398
    #1 360modena2003, Apr 8, 2023
    After replacing the timing chain, new exhaust valves and fuel distributor rebuild, the right side bank is running rough at idle and running much richer.

    I've tried adjusting the CO, but no avail, the right side is running much richer.

    I had doubts if it was related to timing, so I removed the covers and they are nearly right on the mark (flywheel right one the large marking PMS 1 - 6).

    Any ideas, does the timing look right?

    Thanks


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  2. raemin

    raemin Formula 3

    Jan 16, 2007
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    #2 raemin, Apr 8, 2023
    Your timing could be much worse without any audible issues.

    As you've rebuilt the k-jet, I would try to swap the distributors and the wurs and see if this could be your issue.

    Also check that one of your cold start injector is not stuck open (easy to swap or disconnect).
     
  3. 360modena2003

    360modena2003 Formula 3

    Jul 11, 2009
    2,398
    #3 360modena2003, Apr 8, 2023
    Hello Ramin, good to see you back, appreciate your help.

    I've removed the injectors, and tested them connected to the distributor, they are all atomizing very poorly at idle and part throttle (by pressing the metering plate).

    I've also tried with a new injector, and same issue.

    I have the 5.5 BAR of fuel pressure and the correct volume as well, so something is wrong with the distribution head.

    Could the problem be the quality of the diaphragm? I was told if it is too tight, it will not allow sufficient fuel through.

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  4. raemin

    raemin Formula 3

    Jan 16, 2007
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    #4 raemin, Apr 8, 2023
    I've just taken mine out of storage this afternoon and same story on startup. Car sat for six months, so old gasoline, but new pumps, filters, injectors, distributor seals. Also Tank recently cleaned. So I would assume that either the gasoline did not age well, or I made a mistake during the k-jet rebuild.

    Diaphragm could be the issue, as I suspect there is an up/down side. This was obvious to me on the second distributor, but I did not pay attention while refurbishing the right one...

    Could also be the WUR as I replaced the seals on the left bank, not the right one.

    So that's another gremlin to chase, but as it disapeared after an Italian tune-up, I will give it another try tomorrow with a fresh tank, and hopefully it's gone. Otherwise, new seals for the WUR, and distributor to the Bosch Service flowbench (from time to time, specialists do deserve their fees).
     
  5. 360modena2003

    360modena2003 Formula 3

    Jul 11, 2009
    2,398
    #5 360modena2003, Apr 8, 2023
    The WUR would provide cold enrichment until a certain temperature, it is running rich from the very beginning and it is definitely richer than the other bank, so I don't think it's the WUR.

    Cold start injectors are not leaking or open either.

    Good suggestion with swapping out the WUR and seeing if it makes a difference.

    I will take pictures of the injector spray at idle/part throttle position compared to WOT.

    I have a suspicion the diaphragm may not be the right quality, I've ordered a new kit from Germany and will see if there is a change.

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  6. raemin

    raemin Formula 3

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    #6 raemin, Apr 9, 2023
    Just check your control pressure so as to discard the WUR. Then check for one injector totaly off.

    Then the more complex stuff: check if atomization is better if you reduce/increase all the individual injectors setscrews. There is a sweet spot fo the injector port discs that push the diaphragm. If all the discs are too high or too low you can compensate with the CO screw, but this puts tension on the a diaphragm so the low/high rpm could be seriously unbalanced (?).
     
  7. 360modena2003

    360modena2003 Formula 3

    Jul 11, 2009
    2,398
    #7 360modena2003, Apr 9, 2023
    I adjusted the individual port set screws as to get 160ccm2 at full throttle as per the manual.

    Perhaps I could turn each one 1/4 turn and see if it makes a difference.

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  8. raemin

    raemin Formula 3

    Jan 16, 2007
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    #8 raemin, Apr 9, 2023
    Last edited: Apr 9, 2023
    Are you sure it's rich, and not the blow by sending oil residues to the right bank? I've just removed the blow-by, and the right hose is receiving tons of oil additves. It's actually parafine from my original cheap break-in oil (I know the manual asks for two oil changes when changing oil type, but that's twice as more expensive. Lesson learned) ... At least cleaning the blow-by was an easy fix.

    No idea why these residues would rather go on tge right side though, but right hose full whereas left hose far less clogged.

    See picture of the oil tap mesh screen:

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  9. 360modena2003

    360modena2003 Formula 3

    Jul 11, 2009
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    #9 360modena2003, Apr 10, 2023
    I just noticed that my WUR may be connected to too much vacuum.

    I only have the 400i Bosch manual, but I am assume they are the same.

    Could you take a look on your car if it is the same, it seems the lower connection (#6) should be connected to "atmospheric" pressure.
     
  10. 360modena2003

    360modena2003 Formula 3

    Jul 11, 2009
    2,398
    #10 360modena2003, Apr 10, 2023
  11. raemin

    raemin Formula 3

    Jan 16, 2007
    1,869
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    #11 raemin, Apr 10, 2023
  12. 360modena2003

    360modena2003 Formula 3

    Jul 11, 2009
    2,398
    #12 360modena2003, Apr 10, 2023
  13. 360modena2003

    360modena2003 Formula 3

    Jul 11, 2009
    2,398
    #13 360modena2003, Apr 10, 2023
  14. 360modena2003

    360modena2003 Formula 3

    Jul 11, 2009
    2,398
    #14 360modena2003, Apr 10, 2023
  15. 360modena2003

    360modena2003 Formula 3

    Jul 11, 2009
    2,398
    #15 360modena2003, Apr 10, 2023
    If you notice, the 412 is connected exactly the other way.
     
  16. 360modena2003

    360modena2003 Formula 3

    Jul 11, 2009
    2,398
    #16 360modena2003, Apr 10, 2023
    But the question is, what would cause it to run so rich?

    The control pressure coming from the WUR varies from 1.2 to 4 BAR, the higher the pressure, the leaner the mixture - but the issue is that I am running rich at idle right from cold start.

    What I know so far:

    1. Timing is correct.
    2. Cylinder compression pressures are correct.
    3. Primary Pressure (5.5BAR and flow 900ccm/30 sec) are also correct.
    4. Control Pressure should be 1.2 at cold and 3.5 fully warm, this I have to test.

    What I am not liking is that the fuel atomization is very poor, only at full throttle does it have a good "spray".

    I just read that the "air bypass" should be closed completely and the idle should be adjusted using the throttle adjustment screws - I will set this up was well, together with the CO using the "1/2 turn back from fuel raising at the port" technique, this should be enough to have a "base".

    I will also swap the WUR and see if there is a change.

    Any further suggestions?
     
  17. raemin

    raemin Formula 3

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    #17 raemin, Apr 10, 2023
    The WUR WOT vacuum enrichment is determined by the difference of pressure between the two hoses, with normaly more vacuum on top hose than horizontal lower hose. So yes it can be the cause of your issue, allthe more since your right bank is connected to the gearbox vaccum amplifier (the disc shapped item).
     
  18. raemin

    raemin Formula 3

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    #18 raemin, Apr 10, 2023
    Air bypass: leave it alone for now. It is meant to adjust pressure when you abruptly release throttle. So leans the mixture.
     
  19. 360modena2003

    360modena2003 Formula 3

    Jul 11, 2009
    2,398
    #19 360modena2003, Apr 10, 2023
    Will also check if the cold start injectors are leaking or spraying fuel.
     
  20. 360modena2003

    360modena2003 Formula 3

    Jul 11, 2009
    2,398
    #20 360modena2003, Apr 10, 2023
    With air by pass I mean the large adjustment screw on the intake by the throttle body.
     
  21. 360modena2003

    360modena2003 Formula 3

    Jul 11, 2009
    2,398
    #21 360modena2003, Apr 10, 2023
    Yes, but I have been looking at all the 412 pictures, and they all seem to be connected the same, very confusing. Like you say, in "normal" operation the upper should have lots of vacuum, and WOT no vacuum.
     
  22. 360modena2003

    360modena2003 Formula 3

    Jul 11, 2009
    2,398
    #22 360modena2003, Apr 11, 2023
  23. raemin

    raemin Formula 3

    Jan 16, 2007
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    #23 raemin, Apr 11, 2023
    Last edited: Apr 11, 2023
    If you decrease pressure of the upper chamber of the WUR this pushes harder / higher the floating disc against the seals that restrict the WUR gazoline outlet, so higher control pressure. The reverse is true, at WOT the pressure drops, so the disc goes down (i.e is further apart from the fuel input and outout, so less control pressure, i.e enrichment.

    That's an oversimplified description because the disc is also held by a spring/pin/sombrero plus the cold start arm. It is actually the diaphragm between upper / lower chamber that pushes the whole disc assembly (spring, pin sombtrto) up or down, but you get the idea...

    I can hardly see how it would work the other way round with vacuum applied to the lower chamber.

    To, validate my assumption, just disconnect WUR vacuum port (top) while engine is running and see if control pressure goes down.
     
  24. raemin

    raemin Formula 3

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    #24 raemin, Apr 11, 2023
    Last edited: Apr 11, 2023
    A small schema from pelicanparts is more explicit. What I call "disc" is 71, Diaphragm is 76.

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    Not all WUR do have WOT enrichment, that's a clever bit of engineering. Brian Leask modifies it so as to make the enrichment "tunable".
     
  25. 360modena2003

    360modena2003 Formula 3

    Jul 11, 2009
    2,398
    #25 360modena2003, Apr 11, 2023
    Yes, same as per the Ferrari/Bosch 400i manual and completely the opposite to what I have on my 412.

    The "upper" chamber goes to BEFORE the throttle plate.

    What is the part number of your WUR?

    Just for the hell of it, I will switch them around and see if anything changes - in theory if they are inverted, I would be getting WOT enrichment at idle, which could explain why it runs terrible at idle but great and full open throttle.
     
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