4.9L Q: Fuel pressure regulator failure? | FerrariChat

4.9L Q: Fuel pressure regulator failure?

Discussion in 'Maserati' started by 71Satisfaction, Nov 20, 2015.

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  1. 71Satisfaction

    71Satisfaction Formula 3

    Jul 15, 2012
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    Art
    #1 71Satisfaction, Nov 20, 2015
    Good afternoon,
    My Bora is running just fine, maaaaybe a touch rich, but I just noticed the fuel pressure is way up at 6psi.

    The past couple of years, fuel pressure has always been stable around 2.5-3.0psi. Fuel runs through the Holley pump, to the filter and regulator housing - which I believe is set to provide 3psi - then up to the carb fuel rail.

    My understanding is the fuel pressure SHOULD be 3psi.

    Before I call MIE for a new fuel filter and regulator housing…

    How does a fuel regulator fail?
    Is running the carbs at 6psi a problem?
    I feel like I smell a bit more fuel odor, but that could just be a trick of my imagination - or could this explain my slightly rich running condition?

    Thank you,
    - Art
     
  2. 5000gt

    5000gt Karting

    Oct 8, 2015
    90
    #2 5000gt, Nov 20, 2015
    Possible diaphragm or spring regulator failure so you're probably running the 6psi direct from the fuel pump which is unsafe. You might blow right through the carbs and fuel might spill on the exhaust.No need to explain what happens next!
     
  3. 5000gt

    5000gt Karting

    Oct 8, 2015
    90
    #3 5000gt, Nov 20, 2015
  4. 71Satisfaction

    71Satisfaction Formula 3

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    Art
    #4 71Satisfaction, Nov 20, 2015
    Thank you for all that.
    The photos and discussion are very helpful.
    I will start by disassembling it tomorrow and see if the failure is obvious inside.
    Cheers,
    - Art
     
  5. thecarnut

    thecarnut F1 Rookie
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    Apr 22, 2006
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    #5 thecarnut, Nov 21, 2015
    The later Boras used a Filter King regulator instead of the Fispa. The Filter King regulators are much easier to find ... just look on ebay.

    I have a box full of dead regulators and not had good luck fixing them . If your car has a Filter King regulator I suggest you just buy a new one for less than $100 and be done with it.

    And yes, 6 psi is way too high, Webers are happier at 2.5 psi

    Ivan
     
  6. 71Satisfaction

    71Satisfaction Formula 3

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    #6 71Satisfaction, Nov 21, 2015
    Thanks for sharing that approach and info Ivan,
    I'll get into it later today and hope to discover/verify the failure, then proceed.
    - Art
     
  7. 71Satisfaction

    71Satisfaction Formula 3

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    #7 71Satisfaction, Dec 14, 2015
    Quick update;
    I removed the fuel filter/regulator unit to my work bench. The problem revealed itself upon opening the filter bowl: The plastic center ring that holds the sprung plunger in place had worked itself loose. The plunger, spring and ring then fell out into the core of the filter. The reason the center ring fell out was due to poor swaging around the rim.

    I reinstalled the plunger, spring and center ring - then re-swaged it.

    Viola!

    It holds rock steady at 3.0psi.

    Cheers!
    - Art
     
  8. staatsof

    staatsof Nine Time F1 World Champ
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    #8 staatsof, Dec 15, 2015
    I had one of these regulators on my Bora too. My buddy had the same exact thing in his QV DD Countach. The brass fuel connectors are simply pressed into the pot metal. The day on of his just popped out and pumped fuel everywhere was the day I went out and bought a high quality one instead.

    There are lots of treacherous spots for fuel fires on these Italian beasts with webers. The fuel rail is pretty big one as well. I lost 3/4 tank of gasoline on a warm spring day once in an hours drive. It all poured into the V on the engine. Fortunately Maserati has a drain hole drilled at the rear that pours out over the clutch. Even more fortunately might never caught fire! :eek:
     
  9. 71Satisfaction

    71Satisfaction Formula 3

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    #9 71Satisfaction, Dec 15, 2015
    Classic Italian cars… a good reason to quit smoking…
     

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