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Thread: fuel tank holds pressure

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    fuel tank holds pressure

    Okay I need help quickly. Fuel tank on my 07 is holding pressure until I unscrew the fuel cap. I recently had the head off for new head gasket. Wasn't holding pressure before the new head gasket. Iv tried cleaning the tank vent. Still holds pressure. Truck has 250 hp nozzles, twin CP3, and an air dog 2 165gpm. I don't know what else to do or to check. Any help is greatly appreciated at this time.


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    Old & Grumpy! Polaraco's Avatar

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    07 5.9 or 6.7? I don't think it matters, but before I look at the FSM. I have an 04


    2003- 3500 RWD Automatic.
    S & B intake, BD Intercooler, Pusher Air Horn, MM3 Double R Tuning, Turbo Timer, electric Flex-a-lite fans, FASS 95,
    50 HP tips, upgrade to 351 turbo, 3.42 gears, Twin air compressors, air bags, Remote dual oil filters, Hellwig sway bar, Front Winch. Home made Fuel Heater, BD Exhaust brake with Torque Lock. Tons of TLC

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    It's a 6.7, and what exactly does fsm stand for?


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    fuel tank holds pressure

    FSM = Factory service manual


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    Old & Grumpy! Polaraco's Avatar

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    All indications are the venting is done through the fuel cap. Which is what I figured. There is no vents on the tank. It's done that way to prevent fuel spills in roll overs.

    There are only 2 lines on the tank. one is the suction and one is the return. The thing you think is the vent is an air purge off the top of the tank. It lets any trapped air vent back into the filler tube so you can fill the tank.

    I'm thinking the vent on the fuel cap is stuck, Give a couple of smacks and see what happens. If it relieves the pressure, replace the cap. Let me know what happens. That's the best I can find.




    2003- 3500 RWD Automatic.
    S & B intake, BD Intercooler, Pusher Air Horn, MM3 Double R Tuning, Turbo Timer, electric Flex-a-lite fans, FASS 95,
    50 HP tips, upgrade to 351 turbo, 3.42 gears, Twin air compressors, air bags, Remote dual oil filters, Hellwig sway bar, Front Winch. Home made Fuel Heater, BD Exhaust brake with Torque Lock. Tons of TLC

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    If it's not the cap, could excessive fuel return like a CP3 from the twin pumps or a crossover tube cause the tank to build pressure? This is just a really odd problem I can't figure out. Truck performance wise runs just fine.


  7. Top Of Page | #7
    Old & Grumpy! Polaraco's Avatar

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    Well yes, but the pressure is pretty spent once it gets to the return. The cap is the only vent you have.

    See how long the tanks keeps pressurized. Turn it off and wait a bit before cracking the tank.

    If the return pressure it that high, you'd hear the cap venting while it was running.

    A cap can cause a vacuum in the tank too.


    2003- 3500 RWD Automatic.
    S & B intake, BD Intercooler, Pusher Air Horn, MM3 Double R Tuning, Turbo Timer, electric Flex-a-lite fans, FASS 95,
    50 HP tips, upgrade to 351 turbo, 3.42 gears, Twin air compressors, air bags, Remote dual oil filters, Hellwig sway bar, Front Winch. Home made Fuel Heater, BD Exhaust brake with Torque Lock. Tons of TLC

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