Could it be that your vent line has a uphill/downhill portion in it?
That could be one reason that the fuel won't fill the filters. What I
*think* is happening is this: You run the header tank low by using
fuel from it instead of the tanks when you unport the wing tanks in
your descent. Then with the plane at ground attitude, fuel tries to
come down the fuel lines through the filters and into the header
tank. Some does (maybe), but apparently not all unless you "crack the
seal". I believe that when the fuel tries to flow into the header
tank it is trying to overcome air trapped inside the header
tank....trapped because of fuel that is trapped in the uphill/
downhill vent line, and can't be pushed uphill by the downflowing
fuel in the fuel lines. I've had the same thing happen with my
plane.....watching the vent line empty during the descent (and of
course the fuel line is emptying at the same time....and I've been
lucky enough to tip the plane to an attitude that allows for a "mid-
air re-fueling" if you will. But I was very careful to make certain
of there being NO uphill/downhill sections in my vent line.
It would seem to me that this scenario that I just suggested would
require just a certain amount of fuel trying to come down the fuel
lines *versus* a certain amount of fuel trapped in the uphill/
downhill vent line, or a certain amount of volume of lines for this
to happen.
Lynn Matteson
Kitfox IV Speedster, taildragger
Jabiru 2200, #2062, 805.4 hrs
Countdown to 1000 hrs--195 to go
Sensenich 62"x46" Wood prop
Electroair direct-fire ignition system
Rotec TBI-40 injection
Status: flying (and learning)
On Nov 2, 2009, at 7:38 AM, bjones@dmv.com wrote:
>
> This extended discussion on fuel flow issues has been just the sort of
> thing I want out of the list sereve.
>
> When I unport my right wing tank during a prolonged descent with
> low fuel
> (model IV with large tanks) I watch fuel drain down out of the vent
> line
> until the glass tube inline filter housing empties and does not refill
> unless I crack the seal on it on the ground, then fuel instantly
> flows.
>
> This has occurred several times even with new filter elements, clean
> finger strainers in the tanks, new fuel lines throughout, and lots of
> attention to straight fuel lines between wing tanks and header tank.
>
> Rather than removing the in line filter elements, I may try placing
> some
> larger openings in the elements. The idea being less resistance but
> ability to monitor for crud.
>
> Thanks to those who have posted comments and to the list serve
> manager for
> making this (and other discussions possible.)
>
> B J
> N154K model IV
>
>
>> <flyboytr@bellsouth.net>
>>
>> Sorry...I missed that... No, I have baffles in the tank. Can't
>> see that
>> area of the tank. ...which I could! :?
>>
>> --------
>> Travis Rayner
>> Mobile, AL
>> Skystar Vixen, N-789DF
>> Continental IO-240, Prince P-Tip Prop
>> ADI-II Autopilot
>> AnyWhereMap Navigation with weather
>>
>>
>>
>>
>> Read this topic online here:
>>
>> http://forums.matronics.com/viewtopic.php?p=270320#270320
>>
>>
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>
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