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85' QV takes a while to start cold?

Discussion in 'Technical Q&A' started by 308GTS, Dec 22, 2003.

  1. 308GTS

    308GTS Formula 3

    Dec 27, 2001
    2,220
    TN
    My 85' QV takes a while to start cold. Has anyone had this before. It will start after many cranks. I was thinking maybe the fuel accumulator or leaky injectors. Strange thing is after warm it fires right up. Normally on 308s they have hot start issues. My accumulator doesn't have a vent line attached so I couldn't see if any fuel was in it to see if the diaphram was leaking.
     
  2. KKSBA

    KKSBA F1 World Champ
    Rossa Subscribed

    Oct 31, 2003
    13,754
    SBarbara-La Jolla CA
    Full Name:
    KKSBA
    I had the opposite problem. Cold start instananeous or a few cranks. Warm start (within 5 to 45 minutes of shut down) several cranks. Warm start after an hour or so, instantaneous usually.

    A new fuel accumulator didn't solve the problem. New injectors did.

    You however have a cold-start issue so maybe I would lean towards the accumulator than the injectors.

    My injectors were leaking pressure causing fuel delivery problems after a few minutes.
     
  3. f355spider

    f355spider F1 World Champ
    Rossa Subscribed Owner

    May 29, 2001
    17,058
    USA
    Full Name:
    Hugh G. Rection
    I'm no mechanic, but I think it may be something else entirely...like something specifically in the cold start circuit...look here for details on how the FI system works:
    http://www.auto-solve.com/mech_inj.htm


    KKSBA, my 328 is currently in the shop for your exact symptoms. My Ferrari tech says the pressures seem normal so he suspects leaky injectors as well, and while we have 8 brand new injectors that will be installed, he is going to test each of the old 8 injectors to confirm the that this is the proper diagnosis. (he's thorough)
     
  4. Ferrari_tech

    Ferrari_tech Formula 3

    Jul 28, 2003
    1,527
    UK
    Full Name:
    Malcolm W
    You need to carry out a fuel pressure test on all the injection components, with special attention to the "cold" control pressure, also if the auxillary air device does not open this will effect cold starting. The easiest way to check the auxillary air devise is as follows :-

    1. Engine must be cold
    2. Disconnect the electrical plugs that feed the auxillary air device
    and the warm-up regulator
    3. Disconnect both air hoses at the auxillary air device
    4. Because the two hoses are located opposite each other, a visual
    check can now be made to see if the blocking plate partly
    closes the opening. (a mirror may be required to get a good
    view)
    5.Replace the electric cable on the auxillary air valve
    6.Bridge the electrical safety switch and switch the ignition on -
    after a maximum of 10 minutes the opening in the auxillary air
    device must be completely closed by the blocking plate.
    7. If the plate does not close, check the power supply -
    minimum 11.5 volts with engine switched off. If voltage is
    okay then replace the valve.

    If you need any other data / fuel pressures let me know and I will post them for you.

    MW
     
  5. 308GTS

    308GTS Formula 3

    Dec 27, 2001
    2,220
    TN
    Thanks Guys. I appreciate it. I would appreciate it if you wouldn't mind posting acceptable pressures. I will check the aux. air valve and maybe that is the issue. I will keep you updated. Thanks Again.
     
  6. Ferrari_tech

    Ferrari_tech Formula 3

    Jul 28, 2003
    1,527
    UK
    Full Name:
    Malcolm W
    Data as requested,

    Fuel pump delivery 750cm³ / 30sec - min voltage 11.5v

    Warm control pressure 2.7 bar - 3.1 bar no vacuum
    3.4 bar - 3.8 bar with vacuum

    Primary pressure 4.5 bar - 5.2 bar

    Injectors opening pressure 2.5 bar - 3.6 bar

    Leakage test for entire system, pressure must hold
    after 10 mins 1.7 bar
    after 20 mins 1.5 bar

    Cold control pressure depends on ambient temperature see attached
    fig 24.

    MW
     
  7. Ferrari_tech

    Ferrari_tech Formula 3

    Jul 28, 2003
    1,527
    UK
    Full Name:
    Malcolm W
    More info - Thermo-time switch chart

    Good Luck


    MW
     
  8. Ferrari_tech

    Ferrari_tech Formula 3

    Jul 28, 2003
    1,527
    UK
    Full Name:
    Malcolm W
    Just noticed that the control pressure chart is for European spec, don't think there is a big difference, but will look into it.

    MW
     

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