REFLECTOR: FUEL FEED
Jim Sower
canarder at frontiernet.net
Mon Feb 14 10:04:28 CST 2005
I don't have individual overflow vents. Mine "T" together at the top of
the firewall. I didn't think that would make any difference. As for
intermittent, gas caps sealing better one time than another could
explain that. One thing that I believe would help a lot is a 1/2" line
from the strake to the tank. I haven't a thing to support this notion,
but I believe it would help. In any event, if your fuel feeds evenly,
you should feel very blessed IMO.
I have no idea in the world why it varies so much from plane to plane
... Jim S.
John Dibble wrote:
> Jim,
> Sounds like you have (had) the extreme case of uneven fuel flow. The
> fuel resistant lubricant seems to have helped for me. What is
> baffling is how inconsistent the problem is. Sometimes the tanks
> remain even, other times the right tank level drops first. However
> when I am down to 20 gallons total, the tanks are always close to even
> (which is all that really matters). Not sure if the levelness has to
> do with the amount of fuel, or that I have descended, on approach to
> my destination. I have overflow vents on each tank so that may make
> my situation different.
>
> John
>
> Jim Sower wrote:
>
>> Tom,
>> My assymmetric flow drove me NUTS for nearly two years. Almost
>> always the right tank would transfer but the left one wouldn't (on
>> several occasions it was the other way around). I tried just about
>> everything:
>> 1. Re-plumbed the vent system with larger lines. Made it as
>> symmetrical as possible.
>> Nothing.
>> Blew into the vents to see if they worked OK. They did.
>> Tested the gravity feed of each tank through the sump into bucket(s)
>> and timed each side from full to empty. No significant difference
>> between tanks in gravity feed to empty.
>>
>> 2. Shimmed the rudder(s) to ensure the ball was centered.
>> Nothing.
>> Sometimes, if I kicked in full rudder and flew in a max crab for
>> about 10 minutes, the "reluctant" tank would get caught up a little.
>> Not a viable solution, but some help when the "eager" tank was
>> running low and I really needed some fuel out of the reluctant tank.
>>
>> 3. Sealed the fuel caps with several different products.
>> Nothing.
>> Taped over the fuel caps to totally seal them.
>> Nothing.
>>
>> 4. Tried venting and not venting the sump tank
>> Nothing.
>>
>> I went from pillar to post, trying everything anyone suggested
>> (having done nearly all of it on my own already). No change. Right
>> tank got down to 5 gal with left tank still indicating 20-25 gal.
>> There were times when the left tank /looked/ like it was trying to
>> transfer, but didn't really. That caused a flame out and I had to
>> dead-stick out of Canada to PHN in Michigan. I couldn't get
>> *anything* to work.
>>
>> Finally, I acquired a couple of [JC Whitney] electric selector valves
>> and installed them between the strake and the sump as shutoff valves
>> (capping off most of the nipples). Now I can DE-select the eager
>> tank and force the fuel pump to "suck" the fuel from the reluctant
>> tank (this will NOT work if the sump tank is vented). I still get
>> assymmetric transfer, but I can fix it with the flip of a switch (the
>> switch has a feature that lights an amber LED on the panes whenever
>> one of the valves is closed. I keep both tanks selected most of the
>> time, and de-select the right one periodically to keep things even.
>> They also make convenient maintenance shut-offs.
>>
>> I went after the problem in what I thought was ascending order of
>> difficulty: carefully checking out the vent system and insuring it
>> worked OK, checking rudder trim and keeping the ball centered,
>> sealing the fuel caps (first with tape to see if it was an issue at
>> all, and then with various chemicals).
>>
>> The selector valves were what I got down to. Installed them when all
>> else failed.
>>
>> Hope you have better luck ... Jim S.
>>
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