Fuel pressure regulator to suit carb, return line, fuel pump questions.

[Jrad]

Have done a forum search, but nothing really returned my specific questions.

Engine: 4AGE, converted to 40mm Mikuni/Solex carbs
Fuel pump: 4-7 psi Facet pump
Car has an ADM fuel tank, and I'm unsure of the internals of it in terms of operation.


I've got a couple of questions in regards to setting up my fuel system.

Do I need to run another internal pump in the ADM tank, or is the Facet external fine as the sole pump for application?

When running a fuel pressure regulator, do I need a bypass style in order to retain the return line? How important is this return line?
What regulators are out there for a 3-5 psi pressure range? Speco have a 1-6psi but no return, similar to a Holley. I'm cautious of buying a Sard or Tomei 1-8psi as there are so many fakes on the market. Similar, I wanted to run a gauge on the FPR, as it's important for the carbs to have an accurate fuel pressure.

Also, how are people typically wiring up their fuel pumps? If wired to ignition, it will only pump when the car is on. However if the engine stalls, the pump will continue if the ignition is on.

Thank you in advance!

[tottacrolla]

If this were originally in a fuel injected car then I would say ditch the Facet pump and buy a fuel injection to carb FPR, not too expensive and kills two birds with one stone.
If you are stuck with the Facet pump then it can be fitted on its own somewhere between the tank and carb, no tank return is required.
Whilst the pump will continue to run with the ignition on, once it reaches a certain pressure it will stop pumping and just maintain the pressure but in the event of the fuel line being broken it will continue to pump fuel out if the ignition is on.
The aluminium Malpassi "filter king" regulator / filters were popular in their day. I would be wary of the glass type as the glass can break in the event of an accident.



There is a Malpassi FPR only version also available.

[Hen may possibly be a nut]

You should run a tachometric relay (can be found in VK?? Commodores) so the fuel pump only runs when the engine is running. They use a similar thing in gas conversions, so they should be available from there too.

No need for an intank pump to feed the Facet. It can suck fuel up from the tank.

Hen

[Jrad]

Thanks for the advice on both counts. Interesting about the relay - I shall do some further reading on them. I'm interested in having a relatively "safe" system.

The facet is being used as we had a new one laying around (dad was going to use it as a booster pump on his 6.6L Trans am, funny that it can act as a sole pump on our little engines!)
Car was never originally EFI. Was an ADM with 4AC engine, so has the ADM tank.

In regards to the return line, why doesn't it need to be run? Is that because the pump is variable, and will adjust to the amount of fuel the pressure reg requires? I'm just trying to get my head around how it all works. A no-return system is easy to source, as there's a lot more pressure regs available.
I was reading (on a corvette forum) a lot of the return/returnless systems are basically based on emissions control. Related to heat and vapour recovery. Can someone confirm that?

[tottacrolla]

The carbs have float chambers that fill with fuel and once full the float closes a valve that stops any further fuel entering hence there is no need to run a return to the tank.
It is a very simple system that goes: tank - fuel pump - regulator - T piece to carb 1 and carb 2

[Hen may possibly be a nut]

That chat about returnless systems used for emissions relates to EFI returnless systems. Where the fuel pumps varies its speed to keep the fuel rail at the right pressure without the need for a return. That discussion is not relevant to your situation with carbs.

While I'm not experienced with them (never finished my carb'ed project... yet) I don't see a big drama about returned or returnless pressure regulators. Just find a reg that gives the pressure you need and set it up as required. As stated above, you just need enough pressure to fill the bowl of the carbs, and not so much that the needle valve gets forced open, causing the bowl to overflow.

[Jrad]

Makes more sense you saying with the EFI systems, as I was talking with a friend about it running a pressure regulator and he was a bit confused when I explained my situation.

I'm still getting my head around it all, haha.
Say if a maximum 7psi is being pumped up to the regulator, and the carbs require 3.5 psi, how does it release the pressure/where is the excess pressure going to?
Does the fuel pump sense that it doesn't need the 7, and back off?

I've just done this most basic fuel system diagram (Ignoring the charcoal canister and small bits)
This is pretty well it if it's not running a return line, right?

[Jacobxxx]

I ran a facet pump with no reg, worked fine for the 2 years I had the car.

4age with twin 40 dellortos. Car surged a few times when I was running a regulator, didn't have the issue when I got rid of it.

[-ollie-]

I read somewhere that you need to use 3/8" (6AN) fuel line for both main and return line, can anybody on here confirm that? I guess with a carby setup you don't need a hard line all the way from the tank to the carb like you do in an EFI setup, so you can just replace the stock lines with braided lines if you do need a bigger diameter line?

[-ollie-]

Bump!

Anybody know if you need to change the fuel line when installing carbs from factory hard lines? If this is the case, do the fuel tank outlets need to be changed to match the fuel line?