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K-Jetronic issue solved

Discussion in '308/328' started by Albert-LP, Sep 20, 2021.

  1. Albert-LP

    Albert-LP F1 Veteran
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    Sep 1, 2010
    7,143
    around Modena, Italy
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    Alberto
    #1 Albert-LP, Sep 20, 2021
    Last edited: Sep 20, 2021
    I restored my 208 GTB turbo (the red one) in 2016: since then the car worked only with a Bosch Fuel distributor ("dosatore") that I borrowed from Toni Auto, as the car didn't work with the OEM one, despite three attempts made to fix it.

    Finally I found a true expert of those K-Jetronic items and I gave back Toni his Bosch Fuel distributor: now the car works better than new. The Injection guy, whose name is Simone Lanfranchini from Novara, Italy, serviced the Fuel distributor, the Warm Up Regulator (WUR) and the Auxiliary Air Valve (AAV). Simply fantastic!

    The cars produced by Ferrari worked well: if they don't work well today, means there is something to fix.

    ciao

    P.S.
    The "BUG" was an alterated (by the previous owner mechanic, I suppose) FD, with some very small parts not factory placed (outplaced: from 0.1 to 0.3 mm wrong positions): the specialist checked every single position and dimension, doing the corrections and right settings every time he found anything wrong.
     
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  3. BigTex

    BigTex Seven Time F1 World Champ
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    Dec 6, 2002
    75,247
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    Bubba
    Well done!!!

    My friend would always say that:
    "It ran well, when it left Maranello!"
     
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  4. Dr Tommy Cosgrove

    Dr Tommy Cosgrove Three Time F1 World Champ
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    May 4, 2001
    32,613
    Birmingham, AL
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    Tommy
    I have a zillion miles on K-Jet and L-Jet cars going back to 85 and that part of those cars has never been a problem. Not ever.

    If they don't work, it isn't the system/design/concept that is a problem, is't just a busted piece somewhere down in there that can be corrected.
     
  5. miked

    miked Formula Junior

    Feb 7, 2001
    688
    Cincinnati, Ohio
    Full Name:
    Mike Dawson
    I have owned several cars equipped with the K or KE-jet systems, they are generally a very robust and dependable unit. My experience has been that the main plunger in the fuel distributor getting stuck or binding via fuel varnish, stuck AVV or an out of adjustment WUR is about the only things that go wrong outside of worn out injectors which I consider a maintenance item. I am currently rebuilding the distributor in my Audi ur-Quattro which suffered from a binding plunger due to sitting for a long time. They are pretty simple devices but have very tight tolerances.
     
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  6. Albert-LP

    Albert-LP F1 Veteran
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    Sep 1, 2010
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    Alberto
    100% agree: we did not change anything, only cleaned and adjusted the existing units.

    ciao
     
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  8. SeattleM5

    SeattleM5 Formula 3
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    Ettore Palazzo
    I would second what others have stated in this thread. Over the years I have tested, rebuilt, and calibrated many Bosch distributors (and WURs) and I have found them to be quite robust and particularly reliable in cars that are run regularly. For those cars that sit, varnish and other debris most certainly effect port flows in unfavorable ways. Where it gets interesting is when mechanics (DIY'ers and professionals) start making changes to the individual port adjustment screws in an attempt to compensate for disproportionate flows. This is why it is imperative that you have the appropriate testing equipment to calibrate post rebuild noting that if you put everything back together as you found it after cleaning (adjustment screw lengths, spring seat heights, etc.) the unit most certainly will be out of calibration. See post #8 in the following thread for some additional information which helps support the discussion: How to tell a fuel distributor needs rebuilding | FerrariChat
     
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  9. Martin308GTB

    Martin308GTB F1 Rookie
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    Jan 22, 2003
    4,180
    Black Forest Germany
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    Martin N.
    You are all right, who mention, that long sitting periods are mostly the one and only problem with these FI-systems. Over here in Germany in the 80s there were zillions of daily drivers Bosch K- or KE Jetronic equiped. Like the higher performing Vokswagen cars. And they were reliable cars if driven regularly or better said, used as a daily driver throughout the year.
    I had cars with Bosch K-, L-, and D-Jetronic and the only source of trouble was the auxiliary air valve on the
    L-Jetronic, which I replaced almost yearly. But it was just around $50.00 back then.

    Best from Germany
    Martin
     
  10. Banzairacer

    Banzairacer Formula Junior
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    Aug 24, 2017
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    San Diego, CA
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    Sanjeev Thohan
    I have an 85 308 QV GTS.

    The car starts immediately and idles rough when cold (San Diego so not really cold)- running very rich. When warm it’s like a different car - responsive end quick (still rich).
    A couple of weekends ago took it for a weekend ride and the fuel pump quit, cranked for a minute or so - let the Car sit and it started up again only to go to the next exit and quit again. Back to storage.

    Today
    Instant start. Goes up to 2000 rpm then degrades to 1500 rpm on its own where is stays for a minute or so. Add throttle end its responsive. Release the throttle and the ROM Slowly degrades to 500 and dies.

    Application of the throttle during the sub 1000 rpm is slow to respond, then all of a sudden goes to 2000 at a jump (like a lag) and then degrades again to 500 to stall with no throttle override for the RPM.

    here are the patients history in light of recent issues and recent issues.
    Over the course of the year, We have rebuilt the CIS octopus, replaced the fuel accumulator and the fuel pump, new injectors and bushings, new plugs and wires.
    Corrected and updated some wiring and connections to the fuel pump relay as well as installing the bypass relay (they call it the TR update -testarossa that has a Bosch Porsche 928ABS relay with a fuse now on the ECU plate in the back.

    New distributor on one side the other checked to be working correctly. Coils are working properly
    The AAV (under the expansion tank) seems to be working the WUR is an unknown.


    Seems like an Air fuel issue or a fuel pressure issue.
    HELP!!!!!


    Fuel pump relay.
     
  11. SeattleM5

    SeattleM5 Formula 3
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    Kirkland, Washington
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    Ettore Palazzo
    "Seems like an Air fuel issue or a fuel pressure issue."

    I would agree. When you state that the 'CIS octopus' was rebuilt, am I correct to assume you are referring to the fuel distributor? If yes, did you or the rebuilder ensure balanced flow of all 8 ports after the rebuild as well as confirm system pressure to ensure the internal fuel pressure regulator was set appropriately? Was the control pressure regulator (WUR) adjusted as well? When I perform pre/post fuel distributor rebuild testing I recommend testing with the WUR in place to ensure cold control/warm control/system pressures are all within specification. See post #6 above along with the reference to additional Fchat content within that post which describes the challenges of rebuilding distributors without confirming balanced port flows post rebuild. Also note that after installing a freshly rebuilt, balanced distributor back onto the air flow meter an adjustment in the idle mixture control screw will likely be necessary given that the ratio of the air flow sensor plate/sensor plate lever to fuel distributor plunger will be set to the pre-rebuild fuel distributor flows. At this point I would recommend confirming what your AFRs actually is at start up and after warm up followed by confirming fuel pressures are within spec (cold control pressure, warm control pressure, system pressure). For reference, the 0438100139 distributor fitted to the 85 308 QV should have a system pressure of 4.8-5.4 bar while the 0438140132 WUR fitted to the car should have a warm control pressure of 3.5 bar. Note that cold control pressure is dependent on temperature and barometric pressure. Looking at San Diego weather currently (68 def F, 30.05 inHg barometric pressure), cold control pressure should be 2.0 bar. Hope this helps
     
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  13. Banzairacer

    Banzairacer Formula Junior
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    Aug 24, 2017
    358
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    Sanjeev Thohan
    Thanks @SeattleM5
    awesome input despite my comical description of the CIS fuel distributor. I’m hoping to have a fuel system specialist/guru look at it either from Ferrari or Porsche racing. Let’s see who has the first slot.

    From my purchase the car has always run rich and we couldn’t resolve it with the actions taken.
    I know that these systems become bulletproof when dialed in and that this dial in process can be patience breaking.

    Sanjeev
     

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