REFLECTOR: FUEL FEED

John Dibble aminetech at bluefrog.com
Mon Feb 14 07:30:11 CST 2005


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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