We are currently using this fuel system arrangement on one of the race cars, but may not have fully understood how the system works before implimenting it.. basically, the fuel pressure gauge will read approximately 3.5psi, but bounces between 2 and 7 a's if there's air in the system.


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Ha's anyone ever successfully run a return style regulator where it dumps the return back in to the inlet side of the fuel pump? In theory, we were thinking this should work, but I think every time the regulator opens and closes it causes pressure spikes at the inlet side of the pump.. any advice or recommendations is welcomed.

To answer some basic questions...

Fuel pump outputs 14psi, weber want ~3psi, we cannot dump the return back into the bladders because there is only one crossed line (-8), and they both needs vents to allow for the fuel level to move freely . We are currently overpressurizing the needle valves and flooding the float chambers...

We ran the system like this at willow springs months ago, but a 5.0L Chevy with 4 webers at full chat pretty much just burns off whatever fuel makes it into the combustion chamber, regardless of fuel spilling into the chokes.. we were blissfully ignorant to the problem.

Couple of thoughts to consider, but certainly don't do anything with them until someone with more experience pipes in.
First thing I know that the stock FI dumps back into the unpressurized fuel tank, so it could be something to consider. -edit- just saw you can't return to the bladders so I don't have any ideas there anymore
Second maybe there is air in the return line that's then getting dumped into the pump? Or the burst of pressure is throwing things off. I assume you're measuring after the regulator?

Yes, this is extremely common on what would be considered a "Surge tank". Its what I have for mysetup. I also run an AN 10 line to my fuel rail.


I have a return from my surge tank to my fuel tank but its unecessary, I only do it to keep the fuel cool.


Basically I have a carb fuel pump that primes my 1l tank, then a Bosch 044 that runs from the tank to the fuel rail, then a pressure regulator that returns it to the surge tank keeping it full all the time. Then I have (unecessary) a line from the top of the surge tank that runs to the main tank.


It must be noted I run about 54psi of fuel from the surge tank to the injectors. But I dont have any idle problems on my tiny 4 cyl with my massive 1300cc injectors nor do I have fuel starvation at this point (Clogged up a fuel filter inline... thats another story) at say 375hp.

Photo of said surge tank before I moved my return line on the tank to the top (Stupid me had it at the bottom )

Perfect. Thanks for confirming I'm not crazy....

We ran some tests tonight that found two notable nuances.

A) we disconnected the system return line, and dumped it directly into the fuel filler neck. Pressure on the gauge appeared to be ~2psi, but raising the pressure on the regulator caused the needle to drop... odd. turned off the fuel pump, watched the needle on the gauge go back around once.. that 2 PSI turned out to be 9PSI. All along we had been pegging the gauge, but the pump builds pressure so quick, we never saw the needle go once around initially. backed the pressure regulator screw all the way out and...hey, 2.5PSI

B)We do have to bleed the system if a main line ever gets cracked and lets a substantial amount of air into the system. the air bubbles seem to get caught in the regulator causing it to bounce pressure +/- 1 psi. This went away as soon as we put more fuel in, and started the car.

So, lessens learned from today... always check fuel pressure with two people. Once on the switch, one on the gauge, and by the nature of the shape of the cells, it requires at least 5 gallons of fuel for the pickup lines to be submerged....

What fuel pressure regulator are you running? If it's one meant for carbs, it probably isn't intended to have a return line. Most FPRs for carburetors are meant to run as a deadhead setup (i.e., no return line).

The Holley FPR (for example) is meant for a dual-float-bowl carb, so it has two outlets, not an outlet and a return. So, if you don't need both outlets, you plug the one you don't need.

Aeromotive A2000 dynamic flow bypass regulator. We needed the volume, and it conveniently has 4 outlets which meant we could avoid the flow restricting banjo bolts and go with normal -6AN fittings.

According to aeromotive''s website, it can adjust down to 2 psi, but we found it stable all the way down to .5psi.