The trouble with AN fittings is they are all male.
  The trouble with AN hose ends is they are all female.
  If you have three or more devices in series say; fuel pump,
  filter and pressure sensor you wind up with a string of
  stuff 2 feet long. Each device must be separated by a hose
  or pipe. Each hose or pipe is a minimum of 2 or 3 inches long.

  The trick is to use a 3D fuel rail in reverse.

  Here is a set up where there are two tanks. Each tank has
  a fuel pump. Each fuel pump has a fuel filter.

  The up side to this is if one tank, filter or pump fails you
  have a back up in the other tank, filter and pump.
  There are scenarios where this does not work out well but
  any system has bad scenarios.

  You merely select tanks with a toggle switch on that tank's fuel
  pump. Fuel is prevented from going to the other tank
  by a one way valve in the hi pressure Walbro pumps.

  Unfortunately with any EFI systems fuel must always be returned to the
  tank it is drawn from or in some cases fuel can be pumped
  over board through the vents. With this system an electric
  actuated valve is used to select which tank the fuel is returned
  to.

  A single common sump tank can be used but unless it is
  cooled the fuel will heat up due to being continuously re-circulated
  through the fuel rails on the engine.

  I digress.

  Here is the fuel rail in reverse trick.
  Explained by the drawings.

  Paul Lamar

not entirely true.

look here...

http://www.aeroquip.cc/fcm2971fbm2971-06x-06.aspx

and here...

http://www.aeroquip.cc/fcm2915fbm2915-06x-06.aspx

You may find a solution that will be both compact and simple.

William Mason

I am sure I won't. :)
In effect I have no fittings at all :)
Just a block of aluminum.

Try PegasusAutoRacing.com
They have the largest collection of AN fittings I have found so far.

Paul Lamar

!@#$%%^ (cursing :)

The limitations of 3/8 aluminum tubing plumbing bit me today. I was not
able to get a simple right angle connection in the space available
due to the limitations of flaring tools and the fact the sleeve will
not slide around 90 degree bends. I used a lever tube bender.

wont-work.jpg

Ideally if one were starting from scratch one would move the fuel pump
back and inch or two but I did not want to punch yet another hole in the structural fuse skin.

Plan B: The next thing I tried was the 270 degree helix trick. A lever tube bender will not bend 270 degrees. Max bend is 180 degrees. So I had to go with
the spring bender. The problem with that is you can not get the spring off the
tubing after it is bent 270 degrees unless it is bent around a 2 inch diameter or larger rod or pipe. Even 2 inches is  marginal. That started to get too close to the control mechanism and the aft panel. I spent all day on it and
it was a pain in the butt.

270-degree-trick.jpg

Plan C: to be tried next week is connect the right filter to the left
fuel pump and the left filter to the right fuel pump next week when I get some
more tubing. Fortunately there is room under the controls. Plan-C.jpg

It is tough squeezing all this stuff under the floor of an RV4,

Paul Lamar