I have a question for people with electronic fuel injection systems.  My
   question involves the tank setup and return lines.   On a Cozy with a
20b.
   I have a sump tank and I planned on having check valves between the wing
   tanks and the back seat sump tank. ( I am using Infinity retracts )  I'm
   not
   using a tank selector valve.  Only a fuel system on/off valve.   I
want it
   simple yet right.  I have 1/2" stainless tubing between the tanks and
   1/2"
   outlet from the sump.  Now I'm concerned about the return line from the
   Fuel
   Injection.  Will the pressure of the heated return lines keep the check
   valves from allowing more fuel into the sump?  I plan on a vented
system in
   all tanks but then worry that any pressure could push fuel out of the
sump
   vent line.  I planned on having possitive air pressure on the vent lines
   during flight by facing the outlets into the wind or "jetstream"

   I've got notes from other past questions on this group that suggest the
   check valves but I'm not sure they are using EFI and I wonder where they
   are
   returning the fuel.

   Rick Irwin



I'll give my take on your questions Rick, have a few questions of my
own. Where in the system is your fuel on/off located? Are your pumps
external to the sump? This has created problems for others, I suggest
pumps inside the sump. I do not have a check valve between selected main
and sump on my system. How large is your sump? The fuel returning to the
sump (if that's where you choose to send it) is not under high pressure.
I do see merit in your concern that ram pressure on the main tank vents
could force fuel out the sump tank vent. Perhaps the sump tank should be
vented back to a main tank or main tank vent?

I do have check valves external to the sump on the outputs of the two HP
fuel pumps before the outputs join to one enroute to the engine fuel rail.

Perry

Rick,
The way  to make sure that the pressure is always equal in the three
tanks is to join the vent tubes, then run a single tubing line to your
positive pressure point.  The vent lines should join at the highest
point relative to the tanks as is possible;  perhaps at the top interior
of the firewall.   The junction must be higher than the liquid level in
any of the tanks.  The vent lines should be routed so as to prevent any
liquid from being trapped in the vent lines.  The single vent line to
your external positive pressure point should run DOWNWARD to prevent
water encroachment into the tanks.  Probably the best place to get a
slightly positive pressure is under the strake near the fuselage.  I
would advise against acquiring the full pitot pressure;  slightly
positive is all you need.  I agree with Paul, the full pitot pressure
on  a fast canard could be enough to bulge your tanks and cause some
damage.  Submerging the pumps in the sump eliminates a host of potential
failure modes;  where to mount, loss of prime, hose leaks, vapor lock,
etc.  Consider designing your sump to accept a pair of automotive pump
cartridges.  Most high pressure submersible pumps contain internal check
valves.  There is no need to duplicate them with external components.
If you are planning to use an EFIS, consider using an extra engine
monitor input to monitor the vent pressure in the sump.  Early awareness
brings the risk associated with a missing fuel cap down to near zero.
In my opinion, the system you have outlined is the best arrangement for
a canard.

Aubrey Thompson


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