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Message
Had a disappointing test flight yesterday. Removed the fuel flow sensor.
Replaced it with clear line.
That vertical clear line started getting air
(vapor?) in it, even after reducing power and pointing nose
downwards.
Something else is going on here I haven't nailed down. Will put
back the fuel tank vent and try again.
Sorry
to hear you're still having troubles with this. You mentioned
wanting to check the fuel pickup, but never said anything about doing
that. Since this is a fuselage tank, I'm guessing that the
pickup is short, and is all located near the bottom of the tank? Is
the whole pickup remaining submerged in flight? If so, that would rule out
a leak on the pickup line, internal to the tank.
Does the
problem get better with a full tank of fuel, as opposed to a partial
tank? As many times as you've had to drain it, I'm guessing
you aren't really topping it off for most of these
tests.
If it were
me, I'd try to get the lines as full as possible on the ground, then pull just a
tiny bit of suction on the fuel tank vent. It shouldn't take much, and you
certainly don't want to damage the tank. If there's an air leak, it should
show up as more bubbles getting into the line, and maybe you can see where
they're coming from.
Another
thought- on my original Kolb Slingshot, I had a clear filter that was oriented
vertically. Fuel came from the tank below, into the bottom fitting of the
filter, then out the top of the filter to the engine above. That damn
filter stayed half full of air ALL the time. I could manually fill it, but
after just a few minutes of running, it would be half full of air
again. I wasn't using clear fuel lines, but if I had been, I'm
sure I would have seen bubbles. I can't tell you how many hours I spent
trying to fix that "problem", but I can tell you that it never changed. I
can also tell you that the engine never missed a beat because of
it. Others saw the same thing, and no one could explain it.
Apparently, that's just how it is.
For a moment,
let's assume that all your work on the fuel lines has proven that there's really
no leak, or problems. How about the carbs? Is there a chance you
have a needle/seat that's sticking partly open. Is there a chance that the
fuel level in the bowls is getting off level enough that it's causing
problems? Just looking for another possibility.
Good
luck,
Rusty
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