Troubleshooting Fuel Pressure

This is already posted in my XR4Ti thread, but thought I'd ask here for greater visibility. The issue I'm having is that the fuel pressure is not rising with boost as it should.

Testing via mechanical fuel pressure gauge at the rail:
-40 psi without vacuum line connected
-30ish psi with vacuum
-When throttle is opened, pressure rises to 40 psi
-When boost builds, pressure stays at roughly 40 psi and the needle bounces but does not climb

Current setup:
-Ford 2.3T
-35lb injectors
-Walbro GSS340 in tank fuel pump
-6AN supply and return lines
-Brand new in tank fuel strainer and in line fuel filter

Results repeat with two different regulators, and changing the fuel filter and strainer changed nothing, suggestions? I'm kind of stumped, the fuel pump should be oversized if anything.

What are you wanting it to do? More pressure on boost? What should it be doing?

Are the vacuum lines are some how hooked up incorrectly. What are the limits of the FPR you are using? It may max at 40. Have you tried crimping the return line momentarily while watching fuel pressure? If it spikes it I a for issue. If not then it I a pump issue. Could be that your pump is going south or can only make 40 psi. Or there is some sort of limiter or bypass in the pump preventing it from making more pressure.

Probably dumb to even ask this but is the filter clean? How about the pickup? Is it clean? If all the above cheacks out I would start looking at a restriction on the supply side. Is a fuel line pinched or is a pickup line collapsing?.

It should add fuel pressure at a 1:1 ratio with boost, so at 10 psi of boost I should see 50 psi of fuel pressure. Previously, it was capable of 60 psi of fuel pressure with the stock fuel lines and the same pump, regulator, and injectors. I have tested it with the vacuum line that typically goes to the boost gauge, and the one for the blowoff valve, no change.

The -6AN fuel line with two layers of stainless braid is not really something I want to crimp.

I would try it with out the filter. On one occation I had one that the filter media was loose and was resyricting the flow. A long shot but worth eliminating as an issue.

I would pinch the return line and see what the pressure does. Before messing with anything this will tell you if it is a fuel delivery issue or a FPR issue.

I think three things could cause this: 1. Clogged fuel filter 2. Bad or undersized pump 3. Bad regulator.

There's not an extra regulator in there somewhere, is there? For example, the RAV4 has a regulator in the tank right after the pump. If you put a motor in it with it's own regulator, you need to bypass the one in the tank. Or you should, anyway.

In reply to Dr. Hess:

Nope, just the one on the rail. The only things I've changed since this exact setup last worked properly are the fuel lines and filters, all of which should be less restrictive- but I've also had the entire drivetrain and the fuel tank out of the car, and had some welding done on the fuel rail.

So this is a rising rate aftermarket fuel pressure regulator? and you sure you have it plumbed correctly?

In reply to evildky:

Stock rising rate for the Ford 2.3T, it's plumbed correctly.

As I said try pinching the return line to see if the pressure spikes.

Maybe that's all the OE FPR will hold? DSM guys used to "crush" the fpr in a vise to make it hold a higher pressure. Perhaps your pump while it might flow a trumpload of GPH can only reach a max pressure of 40 psi?

This was actually solved but I guess I only updated the build thread- there was a piece of an old hose barb broken off inside the in-tank feed line! It looked like it had been there for a while, but eventually worked its' way sideways blocking the flow and causing this pressure issue.