Conversion to EFI : Fuel system

[Shannen Durphey]

First off, I haven't read any of these books, but Bruce gives
practical advice, good for following.

Mitch wrote:
> 
  I am thinking of purchasing the
> same engine and transmission combination (pre-93) from a local salvage yard
> specializing in Camaros and installing it in a 66 Malibu I have which will
> serve as a mule for EFI work.  
 Instead of getting
> custom-made fuel tanks, I'd like to implement the dual-pump external fuel
> reservoir system described in Knell's TBI/TPI book.
> 
> I am working this out step by step.  To discuss this with you folks and
> some other buddies, I have put some drawings up at:
> 
>         http://www.employees.org/~ozyman/carstuff/efi_fuel.htm
> 
> There are a number of vexing issues.
> 
> 1. Where should the main return line go?  Knell's book suggests back to the
> remote fuel reservoir, but I was concerned about heat.  I was thinking that
> it would be best to return the fuel that has been to the intake manifold
> back to the large tank.  If you return it to the small tank, some of it
> goes back to the manifold for further heating.  If you return it to the
> large tank, there is no such problem.
> 
> Now, my guess is it doesn't hurt to do it this way, but I was wondering
> what the logic is for returning back to the remote reservoir.  I asked
> Knell about this, and he said if you don't return to the reservoir you can
> suck air if you run out of fuel from the main tank.  But if you run out of
> fuel you run out of fuel; returning to the remote reservoir will maybe give
> you another minute or so of life.
Add the word momentarily in between "you" and "run", suggesting that
any forces that pull fuel away from the pickup tube in the main tank
cause immediate starvation of the main pump.  Returning fuel to the
remote tank reduces the overall amount of fuel pumped out of the
remote tank and increases the chances that the main pump will recover
from starvation before the remote tank empties.
> 
> 2. What is the air pressure in the main fuel tank?  Is it positive or
> negative?  I am concerned because I thought the charcoal canister works
> with positive air pressure in the fuel tank, and I don't see how it can be
> positive in my diagram.  I have been assured from several quarters it is
> about 1-2psi positive, but was looking for an exlpanation of this, since
> you are always sucking fuel out of the tank.
> 
Well your concern about hot fuel holds the key to that.  As fuel heats
up, it creates vapors.  The gas cap is a check valve that keeps the
vapors in the tank.  Simce the pump isn't picking them up, they have
to go somewhere.  In the early '70's it was out the vent tube, then
came the charcoal canister.  

> 
> 4. Just some general stuff: I am concerned about noise.  One idea I had was
> to make this an assembly and mount it on rubber mounts, like motor mounts.
> I was definitely considering some kind of case or cabinet (steel (like an
> old toolbox) or plastic), but I am concerned about the hazard of buildup of
> fumes, and also cooling for the pumps.  I'd need some way to vent the
> thing.  I wonder whether it would be overkill to build some cooling/venting
> fans into the cabinet.
By "this" I assume you mean the remote tank.  To prevent bomb
situations, your remote tank needs to be full of fuel/vapor and air
free.  This is what keeps the stock tanks from igniting.  But this is
not an area for guessing!
> 
> So if you folks have any advice or ideas on this, please let me know.  I'll
> continue to refine the diagrams as I nail this down.  After fooling around
> with the stock TBI Malibu, I expect to convert the 327 in my garage to TBI
> or port injection the diy_efi way.
> 
Why not find an EFI factory tank that will fit under the Elky? 
Engineering and design work has been done for you, by professionals. 
It's not too hard to change fill tubes and tank strap locations. 
'Sides, the stock 66 tank doesn't have the charcoal canister
connections or return line, AFAIK.  And if you have safety inspections
where you live, seeing non stock fuel system might make inspectors
nervous.
Shannen
> Cheers,
> 
> Mitch Barrie
> Goat Hill, CA