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Thread: PA22 Aux Fuel Valve

  1. #41
    Glen Geller's Avatar
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    Default Re: PA22 Aux Fuel Valve

    Well after 65 years the trusty and much-used aux tank hoof valve has begun to leak.
    Here's my long sad story....
    I had maybe a gallon or two in the aux, and low in the mains so went on a fuel mission.
    Enroute to my favorite affordable FBO for seven minutes I pumped the remaining aux fuel up into right main, then put aux pump/valve control in OFF position.
    Filled both tanks and departed on the right tank.
    My buddy following along in his Tri-Pacer, we went on a strafing mission along the Upper Willamette River here in NW Oregon, and putted around for maybe an hour, so that burned 8~9 gallons, then back to the hangar.
    My other buddy in adjacent hangar called me and told my there was fuel on my hangar floor, apparently from the aux tank.
    I went to the hangar and cleaned up the stains from the floor, I estimate it dripped out 2~4 gallons over several days, so not much liquid seen as it had evaporated.
    Checked right main, nearly empty, and aux tank gauge read FULL, and fuel was up to the cap.
    No odor of fuel so I hit the MASTER and then pumped the 8+ gallons back up to the right main, with intent of returning the next day to see status.
    Sure enough, the aux was 90% full and the right main was 90% empty.
    So now I will explore replacing the O-rings in the Scott parking brake.
    My previous link back in post #19 is no longer valid, but I found a dealer that sells a kit with O-rings and cotter pins, and he even shows which O-rings are required:

    https://lasar.com/seal-kits/seal-kit...seal-kit-scott

    GG
    Glen Geller
    1955 PA22-150 "One For Papa!"

  2. #42

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    Default Re: PA22 Aux Fuel Valve

    In my experience(I've owned a few 22's & 3 with Aux Fuel setup), the original pumps did not have integral check valves & even now if you look up facett pumps some do & others do not. That cable actuated valve is notorious for having bad O-rings over time...

    Quote Originally Posted by 59pacer View Post
    It seems to me that to get leakage from the right tank back to the aux tank would require that the check valve within the electric pump (it has to have one, I would have thought) is leaking, and one of the O-ring seals in the shutoff valve is leaking as well. Am I missing something?

  3. #43
    59pacer's Avatar
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    Default Re: PA22 Aux Fuel Valve

    Quote Originally Posted by doc View Post
    In my experience(I've owned a few 22's & 3 with Aux Fuel setup), the original pumps did not have integral check valves & even now if you look up facett pumps some do & others do not. That cable actuated valve is notorious for having bad O-rings over time...
    In the interest of brevity, I'll amend this post and take out some spurious info.

    We are talking about different things:

    1. the check valve you mention is available as an extra valve in a handful of the ~40-50 Facet barrel type pumps currently available.. It's function is to stop back flow. Our PA22 #476-087 pump doesn't have that valve.

    2. the check valve I'm talking about in my post above, is the check valve in the fuel pickup in the inlet side of the pump. If you take the filter end off the pump, you will be able to see a little ball (looks like nylon or similar) which is held against a seat by a light spring. That is a 'check valve' which only allows the fuel to move forward, not backward. Obviously needed for the pump to function.

    In my aircraft, with the right tank full, and the aux tank empty, it is possible to remove the pump filter cap without a great gush of fuel escaping onto the carpets and ruining my day. Sure, I need some rags to catch the bit that is in filter cap if I'm not careful, but the check valve doesn't drip fuel. It might if it's worn, of course.

    In the PA22 aux fuel system, to get a back flow from the right tank through the fuel pump and the shut off valve to the aux tank requires a leaky internal fuel pump inlet check valve (#2 above), and a leaky shut off valve. Fixing either one will stop the leakage, but working on the idea that a shut off valve should shut the fuel off, personally, that's where I would start. It's not expensive or difficult to replace the o-rings.

    Putting an additional check valve in the system is another fix, but at the cost of a check valve, the assorted plumbing fittings, the time/cost to cut and flare the lines, for about an extra $50 you can get a new pump which slips straight into place and shouldn't leak (?).

    I can't do without the aux tank when we travel out bush where getting fuel can be difficult. Failure of the fuel pump would be a show stopper. I always carry a new one in my 'flight spares' box. As simple and reliable as they seem to be, I have had one fail in another a/c many years ago.

    Further to the above, I pulled my old (Bendix Elmira is stamped on the head!) 476087 apart to see it's internals. It actually has two internal check valves--one as described above, and a tiny one in the bottom of the iron 'cup' type piston. The Facet-Purolator website has big warnings about not using these pumps on aircraft!!

    If anyone is interested, I could post a picture of the disassembled pump in the next day or so.
    Last edited by 59pacer; 01-31-2020 at 05:24 AM. Reason: Updating info

  4. #44
    Glen Geller's Avatar
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    Default Fixing Aux Fuel Shutoff Valve

    As posted somewhere else on the site, the shutoff valve for the auxiliary fuel tank finally gave up the ghost, and I learned a scary lesson.
    Last month I filled both mains and flew around on the right, but landed with 10~12 gallons remaining and secured the plane for the night.
    Next day my flying buddy in the adjacent hangar calls me and says there is lots of fuel on the floor. The valve leaked and 10~12 gallons flowed back into the eight gallon aux tank, and the excess came out the filler neck which is hip-level to rear seat on right side of fuselage. The hanger floor had a big blue stain!
    So here's how I fixed it, really pretty simple.
    (I'm a technical writer by trade, it took longer to write this than to do it. Get comfortable...)
    Master off. Fuel selector in Off position.
    Drain all fuel from the right main tank, and then the aux tank (there's a sump in the left gear leg fairing for the lowest point.)
    Remove the front seat and clean up all the trash and junk from last October's camping trip.
    Take several photos of everything before you start, and at each step. This is always fun to show visiting family on Thanksgiving.
    Disconnect the cable that actuates the valve lever, just break the lock nut loose then loosen the screw, pull out the wire.
    Disconnect the inlet pipe from top of hoof valve, carefully move it 1~2 mm away.
    Disconnect outlet pipe from the electric pump, it's a short pipe heading down to the aforementioned sump.
    Two screws mount the pump to the seat frame, remove them and the ground wire.
    On mine, the power lead is one of those knife connectors and plastic sleeving, disconnect the power lead.
    Pull the pump & valve assembly out and it's easy to work on the bench.
    Hold the big brass outlet nut and unscrew from the valve body, don't lose the aluminum washer.
    Remove the pin from valve stem and lever.
    Push the stem toward the outlet and remove it, there's a MS28775-002 oring in groove on the stem; it was loose in bore of brass outlet nut, I replaced that oring. Test fit in the brass outlet nut, it should hold against gravity.
    There's also an oring in a groove in the valve body, but it still was snug on the shaft and i didn't have a suitable dental pick to pull it out.
    Apply some fuel lube to the orings and bores, like used on the fuel selector valve.
    Reassemble and be sure to clock the valve correctly relative to the pump. Then reinstall in the plane, adding additional insulation around that old knife connector if necessary. Master on and test the pump makes noise and the valve actuates when the control knob is operated. Switch off, master off.
    I put a few gallons of fuel in the aux tank until the gauge moved into the white arc a little. Then master on, pull the knob and pump all that aux fuel up the the right main and the aux reads empty. Feel everywhere around the pump for leaks!
    Switch off, master off, get a beer.
    Check tomorrow that there are no leaks and the aux fuel gauge still reads empty.

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    20200518_155924.jpeg 20200518_155855.jpeg

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    Last edited by Glen Geller; 05-19-2020 at 07:21 PM.
    Glen Geller
    1955 PA22-150 "One For Papa!"

  5. #45
    Administrator Steve Pierce's Avatar
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    Default Re: PA22 Aux Fuel Valve

    Thanks Glen, I merged your thread with the other one so others in the future can get all this great info without having to go to seperate threads. I remember when I got to the hangar one morning and found all the fuel from the wing that the aux tank couldn't hold all over the floor. Kinda scary.

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