Tanks not equalizing

Discussion in 'Peterbilt Forum' started by krazzyboi_44, Jan 23, 2026 at 11:09 AM.

  1. krazzyboi_44

    krazzyboi_44 Light Load Member

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    Apr 30, 2008
    BAton Rouge,Louisiana
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    I have a 389 peterbilt with a paccar, The fuel is being pulled from the drivers side tank filling up the passenger side. A couple days ago I unlatched the drivers side fuel cap while I was on my 10hr break. The tanks leveled out and started back working. Now its doing it again. How can I fix this?
     
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  3. JB7

    JB7 Heavy Load Member

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    Dec 13, 2022
    Laurel, MD
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    Sounds like a venting problem. Check any vents. Some fuel caps are vented so it may be a bad cap. Switch the fuel caps if you can and see what happens.
     
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  4. Judge

    Judge Road Train Member

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    Find vent tube on top. Run small stick or metal clothes hanger to clear blockage. Dirt dobbers have blocked them tubes too
     
  5. blairandgretchen

    blairandgretchen Road Train Member

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    South west Missouri
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  6. '88K100

    '88K100 Road Train Member

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    The vent is frequently the culprit as many hang between tank and frame and get packed with ice during inclimate weather
    Dumping fuel conditioner in tanks can free up the splitter valve, or just park in heated shop overnight to defrost everything
     
    OldeSkool Thanks this.
  7. Tall Mike

    Tall Mike Road Train Member

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    I had that happen on a Junkliner Classic XL I owned in the late 90's.
    A plugged vent hose was the culprit.
     
    Oxbow Thanks this.
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