Fuel injection return lines

[Mike Kimball]

This may sound like a dumb question, but why can't you simply run fuel
return lines for injection systems back to a tee, perhaps ahead of the fuel
valve and fuel pump. Why must it go into a header tank or back to the main
tank? The return line itself would be a header tank of sorts. Problem with
fuel trying to go the wrong way back up the line to the main tank?

Mike Kimball
SR#044




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[LisaFly99]

In a message dated 10/7/02 4:16:39 PM Central Daylight Time, mkimball@gci.net writes:

This may sound like a dumb question, but why can't you simply run fuel
return lines for injection systems back to a tee, perhaps ahead of the fuel
valve and fuel pump. Why must it go into a header tank or back to the main
tank? The return line itself would be a header tank of sorts. Problem with
fuel trying to go the wrong way back up the line to the main tank?

MIKE
That's exactly what I did, no header tank. The only problem is equalizing the return fuel flow to both tanks. I had to put a small restriction in one line to get it close.

Phil&Lisa Smith
N414D
#460R

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[klehman]

That is similar to what Egenfelner ATTEMPTED to do by adding a small
fuel cooler...

The problem is that as the fuel is circulated (and heated) it will form
vapour bubbles when the pressure drops as the bypass fuel goes through
the fuel pressure regulator. The more you circulate it, the hotter and
bubblier it will get. The engine may be especially likely to quit when
power is reduced.

Taking it back to a tank cools it, allows some vapour to condense, and
allows any remaining vapour to separate. Some people have successfully
used small header tanks (a quart or two) as long as it is not located in
a hot spot.

Ken

Mike Kimball wrote:

This may sound like a dumb question, but why can't you simply run fuel
return lines for injection systems back to a tee, perhaps ahead of the fuel
valve and fuel pump. Why must it go into a header tank or back to the main
tank? The return line itself would be a header tank of sorts. Problem with
fuel trying to go the wrong way back up the line to the main tank?

Mike Kimball
SR#044

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[LisaFly99]

Someone wrote not to long ago about retuning injected fuel back to the tanks
instead of using a header tank. Bob.P I think brought up the need to have a
return line inside the tank instead of just dumping it back in through the
fitting. Because it could possibly build up a static charge just running down
the inside of the tank.
This is all from memory so I may have it wrong, but I can see the reasoning
behind it.

Phil&Lisa Smith
N414D
#460R



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[klehman]

I've heard several theories on this discussed. In the automobiles I've
had apart (including the legacy) they usually dump the fuel near the
bottom of the tank with a standpipe. Presumably the standpipe reduces
aeration compared to spraying it in on the top of the tank. With a
header tank that is always full I like to dump return fuel anywhere that
is convenient but preferably at least a little above the fuel outlet
just in case there are bubbles in it. If returning to a main tank I'd do
something similar - through a fitting perhaps near the bottom of the
tank but somewhat forward of the fuel outlet to the engine. I've never
seen any evidence or test results yet that suggests static is a concern.
Even if the idea was valid, the fuel is still well grounded to the metal
tank.
Ken

LisaFly99@aol.com wrote:

Someone wrote not to long ago about retuning injected fuel back to the tanks
instead of using a header tank. Bob.P I think brought up the need to have a
return line inside the tank instead of just dumping it back in through the
fitting. Because it could possibly build up a static charge just running down
the inside of the tank.
This is all from memory so I may have it wrong, but I can see the reasoning
behind it.

Phil&Lisa Smith
N414D
#460R

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[Jason Beall]

My old Bonanza with an IO-470 w/ Continental injection
system had just a fitting on the bottom corner of the
left bladder.

-Jason

--- klehman <klehman@albedo.net> wrote:

I've heard several theories on this discussed. In
the automobiles I've
had apart (including the legacy) they usually dump
the fuel near the
bottom of the tank with a standpipe. Presumably the
standpipe reduces
aeration compared to spraying it in on the top of
the tank. With a
header tank that is always full I like to dump
return fuel anywhere that
is convenient but preferably at least a little above
the fuel outlet
just in case there are bubbles in it. If returning
to a main tank I'd do
something similar - through a fitting perhaps near
the bottom of the
tank but somewhat forward of the fuel outlet to the
engine. I've never
seen any evidence or test results yet that suggests
static is a concern.
Even if the idea was valid, the fuel is still well
grounded to the metal
tank.
Ken

LisaFly99@aol.com wrote:

Someone wrote not to long ago about retuning

injected fuel back to the tanks

instead of using a header tank. Bob.P I think

brought up the need to have a

return line inside the tank instead of just

dumping it back in through the

fitting. Because it could possibly build up a

static charge just running down

the inside of the tank.
This is all from memory so I may have it wrong,

but I can see the reasoning

behind it.

Phil&Lisa Smith
N414D
#460R

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