Fuel Sender/gauge problem fixed.

Discussion in 'Maintenance Bay' started by Southpaw, Aug 31, 2021.

  1. Southpaw

    Southpaw Pre-takeoff checklist PoA Supporter

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    I posted quite a while back of my non functioning fuel sender gauge problem. finally got the system working.
    Some where in its 9200 plus hour past history some one changed out the instrument panel .(Plus much other stuff) The gauges were of the wrong type for the old SW tank senders. Different operating ohm ranges as they were Rochester gauges VS the SW senders.

    I found a set of gauges from salvage company in B.C. from a same year/model wrecked AC.
    Now they read quite accurately .

    Now my left tank seems to fill the right tank . CFI says its just me being uncoordinated.
    After each flight I would hanger the C172 with out filling till the next flight.
    I would fill both tanks, they each took nearly equal gallons. (with in a couple tenths)
    Now with working gauges I see the left will empty and the right will be nearly full.

    It was quite a surprise to find only 5 gallons in the left tank and the right tank nearly full.

    So it's off to coordinated flight training . :)
     
  2. brcase

    brcase Pattern Altitude

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    My somewhat amateur guess for the fuel in balance issue is...
    1. Venting issue.
    a. Fuel cap not sealing properly or the wrong fuel cap
    b. Blocked Vent Line, likely in the crossover to the right tank
    2. Not flying coordinated (probably not likely)

    Brian
    CFIIG/ASEL
     
  3. Dan Thomas

    Dan Thomas Final Approach

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    A leaking right fuel cap will do it. A bad gasket or leaking vent check valve. The low pressure on top of the wing will some pull air out of the right tank and inhibit the fuel flow from it. If the leak gets bad enough it will pull fuel across through the vent line when the tanks are full, and through the fuel system when the selector is on Both all the rest of the time. Fuel can also be lost overboard though a badly leaking cap.
     
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  4. Southpaw

    Southpaw Pre-takeoff checklist PoA Supporter

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    Thank you for this information .
    The gaskets are good , wondering how to check the vent check valve ?
     
  5. flyingron

    flyingron Touchdown! Greaser! PoA Supporter

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    The Cessna Pilot's Association has a page or two somewhere on how to deal with this. It's almost always a venting issue. The biggest issue apparently (and you can verify this if the flow stops being asymmetrical once you get down below half a tank) is that the vent on the left (behind the strut) pressurizes the tank and pushes fuel through the cross tank vent line. Often all it takes is a little bending of that vent tube to correct the problem.
     
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  6. 40YearDream

    40YearDream Pre-takeoff checklist

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  7. Snowmass

    Snowmass Line Up and Wait

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    Since you seem to be flying a Cessna I hope you replaced those ridiculous Phillips head sender screws with hex or socket head screws so you can easily tighten/remove without dropping the headliner.
     
  8. flyingron

    flyingron Touchdown! Greaser! PoA Supporter

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  9. Dan Thomas

    Dan Thomas Final Approach

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    His senders are in the tops of the tanks, accessible though small panels in the top of the wing.
     
  10. Dan Thomas

    Dan Thomas Final Approach

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    Put a bit of 3/8" ID hose or plastic tubing on the tank vent and have someone blow gently into it while you spray soapy water on the cap, especially on those crossdrilled holes in the cap handle. Blowing too hard will make a weak check valve close. Doing this is the way to check the vent check valve, too; you should feel the check valve open, allowing air in easily, and then stop blowing, listen closely at the hose end and you should hear a slow escape of air as the check is closed and the air leaves via a tiny hole in the valve. Don't do any of this with the tanks full. You check the vent crossover line by blowing into the hose (a bit harder) and clamping it shut and running over and removing the right cap; you should hear air pop out. Don't try to inflate the tanks or you could crack something.
     
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  11. Southpaw

    Southpaw Pre-takeoff checklist PoA Supporter

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  12. Southpaw

    Southpaw Pre-takeoff checklist PoA Supporter

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    I would like to thank all of you for your input .
    I showed this to my CFI , he is as curious as I as to how to solve this issue.
    Thank you.
     
  13. Snowmass

    Snowmass Line Up and Wait

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    Cheers to Cessna. I wish mine were on my '64 C-210D.
     
  14. ARTRR

    ARTRR Filing Flight Plan

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    I just cured the same problem on my C-182. I drained the fuel on my left tank, pulled the inspection plates and found the vent tube line was disconnected at the point where it fits into the crossover tube (on the inboard side of the fuel tank). After I reconnected it, reinstalled the inspection plates, and refilled the left tank about 10 gals less than the right, I moved the fuel selector valve to both. Then both tanked automatically adjusted themselves to equal balance. Prior to this, all checks per service manual were testing good. This was what previously confused me. I am an A&P/IA.