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308 QV hesitates at acceleration

Discussion in '308/328' started by Chrill, Apr 7, 2020.

  1. Chrill

    Chrill Karting

    May 31, 2018
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    Christian P Galle
    #1 Chrill, Apr 7, 2020
    Hi all, as the header says my QV hesitates when accelerates and i wonder if anyone have had the same problem. It all began when i changed my fuel pump, filter and fuel lines, it seems to accelerate "pretty good" when coold (not as before though), probebley becouse the cold start is on, and when warm i can only pull the throttle very gently or it will hesitate and burbles. The new fuel pump is a sytec OTP019, how common is it that the pump is faulty when new, or is it more likely somthing else, i can get it to rev up to 7000RPM but only gently on the pedal, and if it hesitates i can move back from the gaspedal and let it catch up and then gentley press it down again and it will accelerate again but only just.
     

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  2. yelcab

    yelcab F1 World Champ
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    Mitchell Le
    #2 yelcab, Apr 7, 2020
    Why did you change the fuel pump?
     
  3. Chrill

    Chrill Karting

    May 31, 2018
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    Christian P Galle
    #3 Chrill, Apr 7, 2020
    Because the tank was full of debris from my old in tank pick up filter, and the fuel pump is before the fuel filter so I can just imagine how much of that is in the fuel pump, although the pump did sound normal and the car was driving and accelerate just perfect.
     
  4. mike996

    mike996 F1 Veteran

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    #4 mike996, Apr 7, 2020
    Replace the new pump with the old pump and see what happens. Seems very unlikely that the new filter and new fuel lines could be the problem. Unless the debris you are referring to consisted of quite large pieces of hard material, it's not likely to have had any ill affect on the fuel pump. It would have just passed through to be caught by the filter. The fact that the engine was running fine before the parts were changed pretty much confirms that the pump was fine.

    As the endlessly repeated old saying goes, "If it aint broke, don't fix it!" ;)
     
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  5. Steve Magnusson

    Steve Magnusson F1 World Champ
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    #5 Steve Magnusson, Apr 7, 2020
    What year and version 308QV?
     

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  6. Chrill

    Chrill Karting

    May 31, 2018
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    Christian P Galle
    #6 Chrill, Apr 7, 2020
    It’s a -85 GTS QV
     
  7. Steve Magnusson

    Steve Magnusson F1 World Champ
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    #7 Steve Magnusson, Apr 7, 2020
    What version? US? Euro? Euro federalized to US?
     
  8. Chrill

    Chrill Karting

    May 31, 2018
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    Christian P Galle
    #8 Chrill, Apr 7, 2020
    Aha sorry, it’s a euro model sold new in Italy and spending his old days in Sweden ;) so no lambda or catalytic converters, or smog pump.
     
  9. Crowndog

    Crowndog F1 Veteran
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    #9 Crowndog, Apr 7, 2020
    Perhaps something else got disconnected (sensor to ecu for example) or a vacuum line opened up or cracked? I only mention these things because it sounds like your are not getting any advance in ignition timing. Or maybe running on one bank.
     

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  10. Steve Magnusson

    Steve Magnusson F1 World Champ
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    #10 Steve Magnusson, Apr 7, 2020
    Yes, the euro system (K-Jet without Lambda) is much more dependent on various fuel pressures being right and/or doing the right thing at the right time. Certainly doesn't hurt to confirm that you've got good spark on both banks per Robert's suggestion, but the next diagnostic step after that is to confirm these four fuel pressures are in spec or not:

    1. Regulated supply fuel pressure
    2. Cold control pressure with vacuum applied to the WUR
    3. Warm control pressure with vacuum applied to the WUR
    4. Warm control pressure with no vacuum applied to the WUR (this is what provides enrichment when you quickly open the throttle -- like the acc. pump on a carb)

    Do you have a copy of the 281/83 Mondial 8/QV WSM? (This covers K-Jet without Lambda.)
     
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  11. mike996

    mike996 F1 Veteran

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    #11 mike996, Apr 7, 2020
    While I respect the other views, since the car was running fine BEFORE you did the work and isn't now, it seems unlikely to me that the problem is related to anything other than the components you replaced. OTOH, if you did some work that you didn't describe initially..all bets are off. ;)
     
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  12. Rifledriver

    Rifledriver Two Time F1 World Champ

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    #12 Rifledriver, Apr 7, 2020
    I agree. Thats where I'd start.

    Not sure why you would replace the fuel pump that the system was designed for with some other brand that may or may not suit the systems needs. The correct pump is readily available from many sources.
     
  13. GordonC

    GordonC F1 Rookie
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    #13 GordonC, Apr 7, 2020
    Agreed with the others, something that you changed has gone wrong. Easiest is to put the old fuel pump back in. Fuel filter should not be an issue...

    Which fuel lines did you change? Where did you source the replacements? Any chance that there is a kink in a rubber fuel line restricting the flow rate?
     
  14. Chrill

    Chrill Karting

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    Christian P Galle
    #14 Chrill, Apr 8, 2020
    Thanks all, I fiddled with the WUR today and found a lot water in the connector, also adjusted the co, was around 5% and turned it down to 1%, and voila the car is all back to normal, my guess is the water in the connector was the problem, or it was just bad connection for some reason.
    Social distancing suit me well agin ;)
     
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  15. Chrill

    Chrill Karting

    May 31, 2018
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    Christian P Galle
    #15 Chrill, Apr 8, 2020
    I think I took out the victory a little to early, still have a spot around 5000rpm where it hesitate at full throttle, but not at lower rpm. Is it possible that I have everything backwards and it actually get to much fuel, because when I lower the co at the fuel distributor it actually goes much better, and then I tune in the idle with the big screw at the throttle body it improved it a little more. My readings at the co meter says around 1% now but it’s an old meter and the car really smells of unburdened fuel, I try to lower it just a little more and see what’s happens.
     

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