Will this diy fuel system work?

[Broncojunkie]

I was discussing this fuel line setup with a buddy and wanted to hear your thoughts. We're looking at using an efi tank and oem efi in-tank pump for carb application.

Everyone talks about doing an efi-to-carb swap using the aeromotive regulator, which I believe is around $300+. I'm not doing an efi-to-carb swap, but I do have a new efi tank and extra pump in my stash. The aeromotive regulator will regulate the high pressure down to carb level. My thought is that setting up the fuel lines in a way that doesn't restrict the flow enough to build that much pressure should eliminate the need for a special regulator. I'll be running new lines anyway, so no skin off my back. Basically, my idea is to create a loop of fuel line going to the engine bay and back to the tank. Although the efi pump is capable of high psi, the open looped line will only allow a certain amount (should be lower) psi. From that loop, install a "T" fitting and run that through a basic regulator and then to carb. Here's a super detailed, very professional diagram:

Thoughts?

[bwguardian]

The regulator needs to be in line and bleed off pressurized fuel not being used. Also, I believe you'll have to get that pressure down to 3-5 psi depending on demand.

[BMW Rider]

The fuel will take the path of least resistance. What you have there will just circulate the fuel back to the tank and supply nothing to the carb.

[quickshift]

You need a 3 port regulator (return style) like the Malory 4309.

EDIT: You can experiment with restricting the return to reach the desired pressure. I have a CFI fuel system on my 84 Cougar feeding my carb set-up using the 4309 and it's been working flawlessly for over 15 yrs.

[Broncojunkie]

You need a 3 port regulator (return style) like the Malory 4309.

EDIT: You can experiment with restricting the return to reach the desired pressure. I have a CFI fuel system on my 84 Cougar feeding my carb set-up using the 4309 and it's been working flawlessly for over 15 yrs.

I figured if I needed to increase the pressure, I could restrict it. Maybe use a smaller line going back to the pump or an additional filter. I believe we spoke about your setup on a previous thread.

[Broncojunkie]

The regulator needs to be in line and bleed off pressurized fuel not being used. Also, I believe you'll have to get that pressure down to 3-5 psi depending on demand.

Why does the regulator need to be inline? Isn't that only for a return-style regulator? If it's getting sufficient fuel pressure, how does it know it's not inline? I realize I may have to play with the return line to dial in a usable pressure. Also, my holley carbs are 6-7 psi iirc, which is why I stated that. Regardless, a good 10-15 lbs of pressure from the pump/main fuel line should be enough to regulate it down with a basic non-return style regulator without blowing it out.

[306gt]

I too run the Mallory 3 port regulator. Been running it for 25 years. I upgraded the feed line from the fuel filter to 3/8 steel up to the regulator. For the return I used the original 5/16" feed line off the regulator back to the tank with a steel 5/16" line soldered into the fuel pump hanger. I use a oil pressure switch that is normally off to turn the pump on.

[Broncojunkie]

Just for a little more explanation as to how this came to mind, I use a similar setup for fueling industrial diesel tanks. The pump pushes through a pipe that is fitted with a "T". From that t fitting, it goes out to a fueling hose and the other t outlet returns back to the main tank. There is a ball valve on the return line to adjust the pressure. This is just a basic version of what I'm thinking of doing with my car.

A carb needs a certain pressure. Most basic non-return style regulators can handle, from what I'm seeing, and 15-20 psi before you have to start worrying about blowing out the diaphragm.

Let's say I was to run a 3/8" fuel line from the pump and just loop it back into the tank. It's going to take a certain amount of psi to push fuel through a certain size/length of line. I don't think it would be a whole lot of pressure needed. Most likely, I'll need a restriction on the return side to bring it up. My point is that a pumps working psi is a balance of the strength of the pump and how much restriction is created in the line.

[gmatt]

Try putting a ball valve in your return, like you have in your diesel set up?

[Broncojunkie]

Try putting a ball valve in your return, like you have in your diesel set up?

While that would work, it's a little cheesy on a car lol! But I think a piece of smaller line or a filter would serve the same purpose.

[quickshift]

Remember when playing with the adjustments, connect the car to a battery charger to simulate running voltage therefore substituting actual running conditions.

[Broncojunkie]

Remember when playing with the adjustments, connect the car to a battery charger to simulate running voltage therefore substituting actual running conditions.

Good point!

[massacre]

The Coyote swap guys use a Corvette fuel filter that is also a regulator. Mounted closely to the tank, so only 1 fuel line goes forward to the engine. Problem with that is i think it's regulated higher than your 6-7 psi requirement.
You could try mounting the regulator closer to the tank as long as you can regulate it down enough?

[Broncojunkie]

The Coyote swap guys use a Corvette fuel filter that is also a regulator. Mounted closely to the tank, so only 1 fuel line goes forward to the engine. Problem with that is i think it's regulated higher than your 6-7 psi requirement.
You could try mounting the regulator closer to the tank as long as you can regulate it down enough?

Technically, this is the scenario I'm trying to avoid. Any regulator that can drop the higher efi pressure down to carb level is going to be expensive and cause more stress on the pump. The way I'm wanting to do it only requires the pressure to go down to, say, 15-20 psi. I'm really not sure where it will be. It all depends on the size of line, type and placement of filter, restriction from the T fitting, etc. My thought is that having an open loop with a modest amount of back pressure will keep the pump from overheating, keep the fuel cooler at the carb, and allow plenty of volume for full-throttle situations. If my completely unsubstantiated calculations are correct, I can do this with a simple, inexpensive design that doesn't require a special regulator... just run-of-the-mill stuff you can pick up at the parts store for $30 or so.

[wraithracing]

I haven't looked into any of this, so I may be completely off base here, but have you considered one of the early EFI lift pumps? The trucks (my dad's 89 F150 5.8 EFI used two EFI lift pumps in the dual tanks and then had a high pressure pump mounted on the frame rail. The lift pumps brought the fuel up out of the tanks and to the high pressure pumps and then that pump bumped the pressure up to the required @40psi. Maybe an in-tank lift pump will do what you want and have enough pressure for your carb setup too with a regulator. Again, I haven't done any research into these pumps, pressures, volume, etc. but maybe it's an option for what you are trying to do. Good Luck!

[BMW Rider]

If you add some form of resistance into the return line, you may get this configuration to work out. The thing about the fuel pump is, it will only reach it's rated pressure against resistance. No resistance - no pressure. That's why the fuel will simply flow back to the tank through the return line unless there is some way to restrict the flow. That is essentially what a flow-through regulator does. What you are trying to do is create a poor mans version. The problem will be to somehow deal with the variables in the equation; fuel demand, flow rate, temperature, voltage, and so on.

For me, that seems like a lot of trial and error and not worth the hassle or grief. I'd opt to change the pump or get the right regulator for the job.

[bwguardian]

Why does the regulator need to be inline? Isn't that only for a return-style regulator? If it's getting sufficient fuel pressure, how does it know it's not inline? I realize I may have to play with the return line to dial in a usable pressure. Also, my holley carbs are 6-7 psi iirc, which is why I stated that. Regardless, a good 10-15 lbs of pressure from the pump/main fuel line should be enough to regulate it down with a basic non-return style regulator without blowing it out.

Because the way you drew and described it initially...which was poorly. Now that you've stated to restrict via line size after the tee I understand. I agree with aforementioned that it's going to be alot of headache and time...but maybe that's worth the effort for you. Any reason not to put a mechanical pump on it like from the factory with a fuel return and be done. You might want to look at line size of said mechanical pump for your scenario...

[Broncojunkie]

Because the way you drew and described it initially...which was poorly. Now that you've stated to restrict via line size after the tee I understand. I agree with aforementioned that it's going to be alot of headache and time...but maybe that's worth the effort for you. Any reason not to put a mechanical pump on it like from the factory with a fuel return and be done. You might want to look at line size of said mechanical pump for your scenario...

A mechanical pump would work too, but most of them don't have a return so you have to worry about vapor lock. I think Edelbrock makes one, but it's a little pricey (not to mention a timing cover for mechanical pump) and I already have stuff for an efi system. Plus, I'm more interested in trying this out just for curiosity sake.

[Broncojunkie]

I haven't looked into any of this, so I may be completely off base here, but have you considered one of the early EFI lift pumps? The trucks (my dad's 89 F150 5.8 EFI used two EFI lift pumps in the dual tanks and then had a high pressure pump mounted on the frame rail. The lift pumps brought the fuel up out of the tanks and to the high pressure pumps and then that pump bumped the pressure up to the required @40psi. Maybe an in-tank lift pump will do what you want and have enough pressure for your carb setup too with a regulator. Again, I haven't done any research into these pumps, pressures, volume, etc. but maybe it's an option for what you are trying to do. Good Luck!

Yes, Trey. Someone (you?) brought it up in an older thread and I plan on using that setup in another car.

[Broncojunkie]

If you add some form of resistance into the return line, you may get this configuration to work out. The thing about the fuel pump is, it will only reach it's rated pressure against resistance. No resistance - no pressure. That's why the fuel will simply flow back to the tank through the return line unless there is some way to restrict the flow. That is essentially what a flow-through regulator does. What you are trying to do is create a poor mans version. The problem will be to somehow deal with the variables in the equation; fuel demand, flow rate, temperature, voltage, and so on.

For me, that seems like a lot of trial and error and not worth the hassle or grief. I'd opt to change the pump or get the right regulator for the job.

I'm not sure I see this so much as a "poor man's version". It's more like a simple version that doesn't require someone to waste $300 on a regulator. Keep in mind, I'm running new fuel lines regardless, so I'm not out anything.

When I set up the inline fuel pump, lines, and bypass regulator in my pace car, it was trial and error too. In fact, I still don't like it and plan to redo it. I'm using a Holley blue pump. It is mounted a little higher than they recommend, but any lower and you'll see it hanging down. As it is now, it's high enough so it isn't noticeable but still too low to add a filter on the suction side. It's a good pump, but noisy and not cheap. An oem style in-tank pump has a sock filter, it's inexpensive, available at local stores, and isn't nearly as noisy.

[gmatt]

There's a guy on youtube (Adam Grover). Looks like he's using the exact set up you described. EFI in-tank pump and tee off return before the regulator.
https://www.youtube.com/watch?v=xewg...8AdamGrover%29

[Broncojunkie]

There's a guy on youtube (Adam Grover). Looks like he's using the exact set up you described. EFI in-tank pump and tee off return before the regulator.
https://www.youtube.com/watch?v=xewg...8AdamGrover%29

Thanks for the link! I figured there had to be some info on this somewhere.