EFI fuel sending unit return line upgrade?

[ChargerST]

I have an EFI tank from Spectra (CR9AFI) which has a 3/8 feed and a 5/16 return line. I don't know why Spectra has such a small return as almost all fuel pressure regulators require a return line at least the same as the feed line...

What would be the best way to replace the 5/16 tube with a 3/8 tube? hard soldering seems to be impossible as the electrical connector is too close.
I think a bulkhead fitting and a fuel resistant hose inside the tank would be my best bet. What do you think?

Here's a pic for clarification:

 

[Darter6]

Back in 2000 I did a Duster with Fast fuel injection.A bulk head fitting is what we used.
Back then you had to make up everything.
Now this is just me, my thought, You won't have any problem just using the 5/16'' return.

 

[furious70]

I would try it first, if you can't keep your psi down where you want it then you might have an indication of a problem

 

[Darter6]

Also I would like to add that we were using 38 lbs injectors.
What is yours ?

 

[INTMD8]

I would try it first, if you can't keep your psi down where you want it then you might have an indication of a problem

Agreed. Highest amount of bypass (flow through return) is at idle. If you can set the fuel pressure a bigger return line won't change anything.

Years ago I built a fuel injected Malibu with over 600hp. Had a 5/16 feed and 1/4 return with zero problems.

 

[69ChargerR/TSE]

Do you need a return? I'm installing the Holley Sniper Stealth and am using this pump.
https://www.holley.com/products/fue...uel_pumps/muscle_car_efi_modules/parts/12-314

 

[451Mopar]

I Have the spectra tank for the Coronet, and the 5/16" return works fine with the 255 LPH pump they provide. I think it would be OK even with a 450 LPH pump.
I think the EFI regulator opening is smaller than the 5/16" return line.

 

[451Mopar]

Here's a pic for clarification:
View attachment 1141936 View attachment 1141937

Check the underside of the tank fitting to make sure none of the wires are shorting to the plate. My B-Body tank had a short. I just rotated the connection that is riveted away from the pickup tube.

 

[70chall440]

5/16 will get it done unless you are making big power (like well over 600)

 

[451Mopar]

5/16 will get it done unless you are making big power (like well over 600)

It's not the power, but the fuel pump volume. The greatest amount of Bypass is with the pump running (100% if it is PWM controlled) and the engine not running.
If you are regulating 3 or 4-bar (which ever pressure the EFI is set for) then all is well.
If using a fuel pump voltage booster, it would need to be checked at the higher voltage level.
Likely the 5/16" return is OK for close to 1,000 LPH pump, but that would require an aftermarket regulator.

 

[ChargerST]

engine will most likely be slightly above 600 hp (~620) and I might be going to a 340 lph pump. FPR is from RobbMc and has a 1/2" NPT outlet!
ok, will try it with the 5/16" return and if not sufficient I'll upgrade it later (luckily the sending unit is easy to remove). Great tip on checking the wiring before installation.

 

[INTMD8]

Another way of confirming return line capability is just loop the feed line to the return with a gauge adapter and no regulator. Run fuel pump, that's your minimum pressure due to return line size.

 

[69hemibeep]

Do you need a return? I'm installing the Holley Sniper Stealth and am using this pump.
https://www.holley.com/products/fue...uel_pumps/muscle_car_efi_modules/parts/12-314

No you don't. I'm using one without a return and I did call the tech line to make sure.

 

[451Mopar]

Do you need a return? I'm installing the Holley Sniper Stealth and am using this pump.
https://www.holley.com/products/fue...uel_pumps/muscle_car_efi_modules/parts/12-314

Interesting, internally regulated, but looks like no way to have the regulator reference manifold pressure?
The EFI tune will have to account for the different pressures across the injector.
That Hydromat stuff is expensive!

 

[69ChargerR/TSE]

Interesting, internally regulated, but looks like no way to have the regulator reference manifold pressure?
The EFI tune will have to account for the different pressures across the injector.
That Hydromat stuff is expensive!

What EFI are you using?

 

[451Mopar]

On the '69 Coronet Convertible, I started with the old version of the Edelbrock XT EFI, and upgraded the electronic to use a FAST 2.0 controller
The Convertible has the Spectra EFI tank and 255lph pump with 3/8" supply and 5/16" return. The 505" stroked 440 Engine is likely only 550 HP max?

On the '71 Charger, I have the FiTech #30012 Go EFI 8 1200HP
This has the Hyperfuel 340 pump in a fuel cell. The lines are -6 (3/8") supply and return. The 500" stroked 400 Engine might make about 700 HP?
I tested the pressure regulator of the fitech with a 450 lph pump, and it had no problem maintaining the correct pressure

On Mikes '69 Coronet, I setup the Holley Sniper system.
Mikes car uses the Holley Sniper (Tanks Inc) fuel tank and 3/8 (-6) supply and return. Not sure what all is in his 496" stroked 383?