Adding a gas tank return, & I have an important question that needs a couple of answers. MD

[Manuel Desantos]

My 86 Trans Am has an LG4 carbed motor in it.  I just finished
installing the TPI and I installed a Holley external In-line pump.  I
have 4 tubes coming out of the stock tank, one goes to a round white
filter looking thing right outside of the tank and the other 3 go up to
the front of the car.
1 on the 3 went to the charcoal canister and the other 2 went to the
mech. Fuel pump that was on the passenger side block of the motor.

What I did, and I hope it works, was leave the one to the charcoal
canister alone, I then cut the 2 metal lines right before they went over
the transmission and ran high pressure transmission hoses from there to
the fuel rail of the TPI unit.  I used two Fuel Injection Hose clamps on
each end of the rubber hoses to make sure that it holds them on really
tight and doesn't leak.  
My main concern right now is that I read somewhere that some of the
return lines on some carbed cars had a small restriction where it goes
back into the fuel tank.  This restriction will cause the fuel pressure
to get very high.  I want to know how to check to see if I have this
restriction without dropping the tank.  I am almost to the point of
starting the motor to break in the new cam and see if the TPI works.

All I have to do is burn a chip then start her up.
Any advice will be greatly appreciated.

Thanks
Manny Desantos

-----Original Message-----
From: owner-diy_efi at diy-efi.org [mailto:owner-diy_efi at diy-efi.org] On
Behalf Of Jeff Meager
Sent: Friday, December 28, 2001 8:01 PM
To: diy_efi at diy-efi.org
Subject: RE: Adding a gas tank return

And note.  Depending on how much your pump flows, you will need to
ensure
that the return goes back into the in-tank swirl pot, not outside
it.....or
the pump will empty the swirl pot - esp if the pump can flow more than
the
holes in the swirl pot - had this before....

LJ

-----Original Message-----
From: owner-diy_efi at diy-efi.org [mailto:owner-diy_efi at diy-efi.org]On
Behalf Of Fran and Bud
Sent: Friday, 28 December 2001 5:15 AM
To: diy_efi at diy-efi.org
Subject: Re: Adding a gas tank return


IMHO
I believe that it is NECESSARY that the return line returns the fuel to
VERY
near the bottom of the tank, well BELOW the fuel level to prevent fuel
aeration.

Another reason to return to the bottom is that fuel flowing thru a line
and
discharging thru open air space CAN (not WILL - just can) ignite the
vapor
space under certain atmospheric conditions.  Fortunately most of the
time
the vapor will be too rich to ignite and besides the weather wont be
prone
to static generation - BUT you only have to be the "one in a million"
that
it happens to for your whole day to be ruined.

More important to using a tank that was not originally intended for EFI
is
an well or a baffle for the fuel pickup to assure that the pump does not
suck air when the fuel level is low or when slosh from cornering, hard
acceleration, or braking can uncover the inlet.

I have had good luck for years in adding things like outlets or returns
by
cutting a 2 1/2" or 3" disc from some heavy sheet metal with a hole saw
and
then brazing tubing or fittings into it and drilling a 4 to 6 hole
pattern
near the outside edge.  It can then be fastened over a small hole in the
tank using cork or neoprene gasket material and bolted down with 4-6
self
tapping sheet metal screws.  If you want to get fancy you can use
threaded
inserts and machine screws.  In any case all of the fabrication is
external
to the tank except for cutting the extra hole in it, and vacuuming out
the
shavings.


Bud

----------
>From: ECMnut at aol.com
>To: diy_efi at diy-efi.org
>Subject: Re: Adding a gas tank return
>Date: Wed, Dec 26, 2001, 2:10 PM
>

>Hey Bruce,
>why does the return line have to be above the fuel level?
>Thanks,
>Mike V
>In a message dated 12/26/2001 4:49:11 PM Eastern Standard Time,
>nacelp at bright.net writes:
>
>>
>>  The oem sender has a restrictor on the CCP line, and the oem return
is
>below
>>  the fuel level.
>>
>>  Has anyone dealt with a similiar situation?, and what was your
answers.
>>
>>  Drilling into the filler neck looks like a real PITA.
>>
>>  Beginning to look like a tank R+R and adding bulk head AN stuff
around
the
>>  sender is the only answer.
>>  TIA
>>  Bruce
>
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