"Minor" fuel leak - Fuel tank air/vapor pressure | FerrariChat
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"Minor" fuel leak - Fuel tank air/vapor pressure

Discussion in '456/550/575' started by luca's308gts, Jun 17, 2019.

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  1. luca's308gts

    luca's308gts Karting

    Dec 16, 2016
    86
    Minneapolis
    Full Name:
    Bill
    #1 luca's308gts, Jun 17, 2019
    I recently noticed a minor gas leak (really just weeping not liquid leaking) which I traced to the connection of the filler hose to the gas tank neck. I could not tighten the clap holding the hose to the neck as it appears to be the type that you 'ratchet over' to close. I then open the gas cap and there was a very meaningful release of air/vapor pressure. Over the past several weeks I've noticed a pressure build up without having started or driven the car, many times. I don't have the leak anymore as the fuel level is down by 1/3 any thus probably below the tank neck, but I do still have the pressure build up.
    So the question(s) is/are; is it normal to have pressure building up in the tank, and could my problem be a faulty "tank ventilation valve", and are there any other valves that could be the cause?
     
  2. luca's308gts

    luca's308gts Karting

    Dec 16, 2016
    86
    Minneapolis
    Full Name:
    Bill
    #2 luca's308gts, Jun 17, 2019
    Sorry, failed to mention the car is a '98 550.
     
  3. Cribbj

    Cribbj Formula 3
    BANNED

    Jan 1, 2011
    2,316
    Cooke City MT, The Coolest Small Town in America
    Full Name:
    John
    #3 Cribbj, Jun 18, 2019
    Bill, "some" pressure buildup in the tank is normal, however it's the function of the EVAP system to relieve it. If you drive your car regularly, and the EVAP system is working as it should, you shouldn't have this issue. The rollover valves on top of the tank are there just to prevent gas leakage in the event of an accident.

    There is another one way valve on top of the tank that collects condensation coming off the fuel cooler and admits it back into the tank, but that should not be the issue either.

    My money would be on a malfunction in the EVAP system.
     
  4. luca's308gts

    luca's308gts Karting

    Dec 16, 2016
    86
    Minneapolis
    Full Name:
    Bill
    #4 luca's308gts, Jun 18, 2019
    Thanks, 2NA services my car so I'll pass your thoughts on to him.
     

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