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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