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Bosch K jetronic fuel injection

Discussion in 'Technical Q&A' started by fasterinred, Sep 14, 2012.

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  1. fasterinred

    fasterinred Rookie

    Apr 25, 2012
    11
    Chester, UK
    Full Name:
    Dean Paul
    #1 fasterinred, Sep 14, 2012
    After 6 years of storage, my Mondial 3.0 QV had a full service including belts and spark plugs etc. At first it ran great. Then on a rainy trip home, it was miss firing. The next day it was running a lot better. But now it runs rough at only 2500 rpm, but idles fine and runs great at all other speeds. The electrical side checks out fine. Bellow 2000 rpm it is smooth, as it is above 3000 rpm.
    Has anyone had a similar probem with a Bosch K jetronic equipped car? It has done less than 500 miles since the full service.
    Dean
     
  2. rustybits

    rustybits F1 Rookie
    Professional Ferrari Technician

    Jan 28, 2007
    2,509
    Somewhere, anywhere
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    Eddie B
    #2 rustybits, Sep 14, 2012
    It still sounds electrical. Have you done a very thorough check of leads and plug extenders? Sounds like it started after getting damp hence my reasoning. It is very easy to miss tracking marks on the extenders, if any have dubious marks on them wrap with insulating tape and retry...
    Other suspects...old fuel? Muck in tank?
     
  3. Mr. V

    Mr. V Formula 3

    Oct 23, 2004
    1,247
    Portland, Oregon
    #3 Mr. V, Sep 14, 2012
  4. vincep99

    vincep99 Formula 3
    Owner Silver Subscribed

    Jun 8, 2009
    1,941
    #4 vincep99, Sep 14, 2012
    I agree with Rustybits, it sounds electrical. With mechanical fuel injection you usually don't have a problem in a narrow range.

    Let us know what checks you did on the electrical side. The best way is to put a scope on the spark plug wires and look at your trace. Compare it with the trace at the speeds where it runs smooth.

    You don't need to buy an automotive scope; you can get an emulator for your laptop and just run a 14-gage wire along your spark plug wire for ~ 4 inches; this will pick up the signal inductively
     
  5. Crowndog

    Crowndog F1 Veteran

    Jul 16, 2011
    7,042
    Fairfield,Pa
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    Robert
    #5 Crowndog, Sep 14, 2012
    In the old days of my Jag poor runnng in damp=distributor cap issue.
     
  6. fasterinred

    fasterinred Rookie

    Apr 25, 2012
    11
    Chester, UK
    Full Name:
    Dean Paul
    #6 fasterinred, Sep 15, 2012
    The first thing I did was to take the rear distributor cap off and check the oring. There was no dampness in the cap and no sign of tracking. I checked the front one as well. I also checked the extenders, as I had read on here about the problems. I didn't pull the plugs out, as they are brand new. With the leads, I checked them with an ohm meter. They check out fine and the ends look good. The tower on the coils look free from tracking as well. This is what leads me to the fuel system. It was stored with less than a gallon of fuel. The fuel filters were changed and the tank fulled before driving it. It has several tanks of fuel through it now. It also requires a lot more throttle to start it hot.
    During the service, it had new cam seals and the valves set as well. I will go back over the electrial side again and pay more attention to the plug extenders.
     
  7. Harry-SZ

    Harry-SZ F1 Rookie

    Mar 29, 2004
    4,522
    Elst (U) Netherlands
    #7 Harry-SZ, Nov 17, 2013
    Did you find out what the problem was? I seem to have the same issue with my 308 QV now.
     

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