Just so we are all on the same page.

Paul Lamar

One item that I don't think has been mentioned in this thread is that
an EFI system that returns fuel to the tank is pretty much self purging.
If you get vapor in the fuel rail, it will soon be cleared. With the
returnless system it can only be purged through the injectors. The
return system won't have much of a hot start problem unless the pump
itself gets vapor locked. In that case the positive displacement pump
would be an advantage I think.

Bob W.

-- N93BD - Rotary Powered BD-4 - http://www.bob-white.com
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3.8 Hours Total Time and holding
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Bob sent me a couple of pumps for my testing collection.
Thanks Bob.

It is easy to check the suction on these pumps. Hook up
a flex hose and start high over your head above a container of fuel.
Power up the pump. Slowly lower the pump until it picks
up fuel. I'll be doing some of that testing in the next couple
of days.

The lower one pound Walbro pump may be the one Tracy is selling.
The two pound pump looks heavy duty but there are no brand
markings other than made in the USA. It is about a half pound
heavier than the MSD unit at 1.5 pound.

The MSD pump I am using now with a return system is drawing
about 4 amps at 12 to 14 volts.

BTW you can make a non return system, by using a pressure regulator
adjacent to the pump near the bottom of the fuel tank or inside
the fuel tank for that matter. Just use an external fuel pressure
regulator. It gets a bit expensive as you will need one for each pump.

Also there is a big no no when using return systems. Never ever suck
out of one tank and return to another. Airplanes have crashed doing that.

Paul Lamar

Paul,
One of the things that most people have been ignoring about in-tank
pumps is that they usually still penetrate a tank wall. The Ford system
uses a flange that also includes a fuel level sensor, multi-pin
electrical connector and all the fuel line plumbing. the trouble with
using these systems can be viewed in the drawings you had in the
previous e-mail. The units seal to a tube or flange and most often are
vertically oriented. The "sock" filter lays on the bottom of the tank.
The vertical orientation allows the pump to get close to the bottom of
the tank.

The designs allow the electrical connections to be in air
outside the tank. The modern car tanks are designed to hold pressure for
sensing vapor recovery. To be safe the electrical connections would need
to be isolated, and a hermetically sealed connection would need to
attached to the flange at the tank. Most of the in-tank pumps don't have
in-tank wiring. I haven't seen any of the in-tank pumps designed to have
wiring penetrate the side of the tank. If one could be found then the
in-tank solution would be easy.

The only trouble would be one pump per
tank. The vertical systems would need to penetrate the tank from outside
the wing! or a stepped area would need to be made near the root. I
really like the idea of the in-tank pump because it could be a much
easier system to plumb. I also like the idea that you could switch tanks
with a simple DPDT switch. No fuel valve and return in the cockpit
either. So far though I haven't seen a pump that would be easy to add.
Everyone let me know if there are good candidates you can't see
everything. I love the elimination of vapor lock too.
Bill Jepson