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308 inconsistent fuel delivery to plugs?

Discussion in 'Technical Q&A' started by pnorman, Mar 12, 2004.

  1. pnorman

    pnorman Rookie

    Dec 30, 2003
    47
    My 308FI has an unusual problem. It will start and run fine but once it's warm and I'm driving it for awhile, it will die and it will try to start but won't until it's been sitting awhile (1 to 2 hours). I have spark but there is no fuel getting to the plugs. I unplugged my cut off switch at the fuel distributer and can hear it running when I have this problem. I have a new filter and accumulator. I've also switched relays. I measured my fuel delivery from the pump and it is 1.7 litres per 30 seconds. I'm getting 11.5 volts at the coils and the fuel pump (previously I was only getting 9 volts until I cleaned my ignition switch). Is my pump bad or do I have another problem? Patrick
     
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  3. thecarreaper

    thecarreaper F1 World Champ
    Silver Subscribed

    Sep 30, 2003
    16,679
    Savannah
    i am not an fcar expert ( yet) but i would assume as with most cars that you need over 12.0 to 13.8 volts for the systems to run properly. seems to me you have a bad positive lead, a bad ground or a faulty charging circuit. this is making the ignition weak and the the fuel pump is not putting out the min pressure required to operate at higher temps / rpm's. michael
     
  4. 308GTS

    308GTS Formula 3

    Dec 27, 2001
    2,221
    TN
    I think your V is acceptable. I would be concerned with the pump. Sometimes a pump can get weak and when heated up and under load it can start going. I would try unplugging your Cold Start Inj. just for the heck of it the next time this happens. Just to be sure. If it happened to start spraying continiously when you car is warm it could stall your engine by being too rich. I think it is worth a try before you spend $200 on a new fuel pump. I think the stock 975 pump flows 1000 cm3,
     
  5. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    21,358
    Texas
    Full Name:
    Steve Magnusson
    pnorman -- What year/version 308? If it's a simple K-Jetronic (without lambda) another issue (in addition to low/poor supply pressure) can be the warm-up regulator allowing the control pressure to rise to too high a value when "warm" (creating an over-lean situation). See this link for some K-Jet background:

    http://www.volvoclub.org.uk/tech/fuel_injection/k_jetronic.htm (Part 2 -- mixture adaptation)

    How long after cold start-up does it die? Does it die before the coolant is up to its fully "warm" equilibrium value? Bottom line is that if someone doesn't make some pressure measurements to really diagnose the problem you might be swapping some fairly expensive gizmos needlessly.

    Good luck...
     
  6. pnorman

    pnorman Rookie

    Dec 30, 2003
    47
    I've been running the engine without the cold start injector to avoid flooding the engine. Thank God it's been warm here in Souithern California...Patrick
     
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  8. pnorman

    pnorman Rookie

    Dec 30, 2003
    47
    It's a non-lambna car. The car is fully warm when it dies. Then last couple of times it ran fine until I intentionally stopped. When I try to restart, it starts for a second, then dies. When it restarts, I can drive a block before it dies. It's definitly fuel delivery because the plugs are firing. After a couple of hours, I can drive the car home even though I've cancelled a tow from the Auto Club twice in the last week. I measured the fuel delivery from the pump 2 weeks ago with the engine cold and it was 1850 ml per 30 seconds versus the 1700 ml 2 days ago warm...Patrick
     
  9. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    21,358
    Texas
    Full Name:
    Steve Magnusson
    Running OK for a while when fully warm and then failing would lead me away from that warm-up regulator theory.

    Based on your new description (fires well every time during starter cranking, but runs only briefly thereafter) I'd start looking towards the:

    "Ignition ECU feeds pulsed signal to tachometric relay which feeds power to close the fuel pump relay which feeds power to run the fuel pump"

    food chain. During starter cranking a different signal is fed to close the tachometric relay directly (and ultimately run the fuel pump via the fuel pump relay) so this will pressurize the system during starter cranking. Next time you have the problem you could try manually jumping the fuel pump relay socket -- probably terminal 30 to terminal 87, but please check the schematic in your year/model/version OM first (or manually jumping the tachometric relay socket, again probably terminal 30 to terminal 87, but that's further upstream).

    Alternatively, the supply pressure measurement would show the same misbehavior (if indeed that that's the problem) -- good/building pressure during starter cranking, but drops immediately when the ignition key is released to the "run" position.
     
  10. Tifosi1

    Tifosi1 Formula 3

    Feb 17, 2002
    1,560
    Pearl River, LA
    Full Name:
    Kelly J. Vince
    We think the battery was dead and he jumped the car with the ignition on. Blew the ECU.

    Car would run great an then flood out.

    Good Luck.
    Kelly
     
  11. thecarreaper

    thecarreaper F1 World Champ
    Silver Subscribed

    Sep 30, 2003
    16,679
    Savannah
    !!!! ouch!!!!!!! ...... oops!!!!
     
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  13. pnorman

    pnorman Rookie

    Dec 30, 2003
    47
    My battery was never dead and I never jumped the car...The ECU's (there are 2 of them) are working fine or the car wouldn't run great till you turn it off and try to restart. New accumulator and filter...It seems more like a fuel pressure thing...I can hear the pump running when the car dies...Patrick
     
  14. tbakowsky

    tbakowsky F1 World Champ
    Professional Ferrari Technician Consultant

    Sep 18, 2002
    16,217
    The Cold North
    Full Name:
    Tom
    Possiable you ar losing your crank signal. Check the connections under the expantion tank in the engine compartment. Be sure the connection is clean and nice and tight. Somtimes these thing have a tendancy to come loose causeing all kinds of silly things to happen. Just a thought...
     

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