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You have to look where your fuel pressure is
generated. Presumably you have an engine driven pump feed the
carburettor. I also assume from your E mail you have an electric boost
pump. Do you have a transfer pump for each tank feeding the ready use tank
(Header)?
If you have the conventional Lancair fuel set up
(with header tank) then as long as you can pump fuel into the header tank you
have more than enough air going into the the main tanks through the vents.
They are not there to blow fuel into the the system but to vent the tank and
allow air to flow in as the fuel flows out. Even standing still with no
speed induced airflow going into the vent will still allow you to transfer fuel
from the tanks to the header. So as long as the vents are clear all the
way into the tank you are OK.
Before you do anything check your pressure
gauge. If your gauge is electric put a "T" in the line to the sender and
connect a mechanical gauge. Compare the two gauges and trust the
mechanical gauge. If all is OK proceed as below
So assuming you fill the header tank you now have a
positive pressure at the carburettor due to the height of the tank above the
carb. Not much to be sure but if the tank is 24" above the carb you have 1
lb/sq inch roughly and yes this will vary with density altitude.
My next assumption is that your electric boost pump
is next in line after the header tank. I do not know what type of pump you
have but there will be some type of pressure regulator to set the
pressure. This may have picked up some dirt in the building process and
the spring loaded relief valve may be held open slightly which will stop the
pressure regulating. Put a pressure gauge on the pump output and determine
the pump pressure. The engine driven pump needs to be checked next and
that needs a bench check. You already know it does not pump.
When you have done all the above and if you have
found nothing then you need an AME!!!!! I know the minimum pressure
is 0.5 psi but for me that is far too close to zero! I would have to find
out what is going on before I flew again. Something is amiss.
Good luck!
Ian Crowe
Ian B. Crowe
LNC2 C-FKRO (Fuel
Injected, no header tank)
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