On the return side the FPR should close as soon as the FP turns off since the pressure is no longer greater than the setting.
On the feed side there usually is a check valve at the pump.
How do you know it's starving for fuel under boost? Are you logging your fuel pressure?
Is the pump big enough for your injectors and boost?

Check your connection(s) inside the tank between the pump and however it is adapted to the hanger.

I have heard that's it's normal for fuel pressure to drop back to zero with an afpr. Is that true? Should a check valve be installed?

Normal as in does it happen, yes. Is that supposed to happen, no.

If the seat for the return port doesn't seal correctly it can leak and as long as that leak is less than how much the AFPR sends through the return during normal regulation it won't effect the AFPR working but will cause pressure to leak down when the pump is off.

On those that do seem to leak people have taken them apart and cleaned up the seat area, removing any burrs, and they then seal.

The only place you MIGHT need a check valve is at the fuel pump end. You need to make sure that everything the pump is pumping goes up the line to the fuel rail and the only way back to the tank is via the FPR. You also need to make sure that the fuel system can correctly regulate the pressure 1:1 with manifold vacuum/pressure.

Turn the pump on, engine off, set you base fuel pressure, and then vary the pressure at the port of the FPR from say 20 inHG vacuum to something more that your normal boost pressure and make sure that the fuel pressure tracks those changes in the reference.

If it does, then you need to do the math to make sure your system is pumping enough fuel to support your injectors @ full boost. Remember there is a pressure loss between the pump and the injectors due to the line resistance and each fitting. So while you might have 43.5 + 25 = 68.5 psi at the injector at 25psi boost the pump has to work harder so it's pressure might be over 70psi and it better not be more than the relief valve in the pump.

Pretty sure when you cut the motor off the pump dies first and the regulator senses the extra vacuum and dumps the fuel pressure in the tank. I’ve never seen a car hold the pressure, usually it’s minimal, less than 5 psi by the time I see it on the gauge.

chrysler kid said:

Pretty sure when you cut the motor off the pump dies first and the regulator senses the extra vacuum and dumps the fuel pressure in the tank. I’ve never seen a car hold the pressure, usually it’s minimal, less than 5 psi by the time I see it on the gauge.

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The gauge on my AFPR (Fuelab) maintains pressure with the Walbro 255 off for a good 30 minutes or more, and gradually bleeds off.

chrysler kid said:

Pretty sure when you cut the motor off the pump dies first and the regulator senses the extra vacuum and dumps the fuel pressure in the tank. I’ve never seen a car hold the pressure, usually it’s minimal, less than 5 psi by the time I see it on the gauge.

Click to expand...

You should test this premise.

At shutdown I would expect the fuel pressure to drop to about it's idle value but the ECU has code that keeps the fuel pump running for a short time after the engine stops generating CAS signals so I would also expect the fuel pressure to rebound to the base pressure quickly before the pump turns off.

As mentioned, unless the FPR is leaking out the return, the injectors, or there isn't a functional check valve at the pump end the fuel lines, filter, and rail should remain pressurized for some time after the pump turns off. In fact the FSM warns you of such.

While my experience is limited to a 1G the fuel systems are pretty much the same and the anecdotal evidence is that the quick pressure leakdown isn't the normal case but an indication of something going on.

By itself it's not necessarily a problem but the OPs report of starving under boost is.

Shut my car off 3 hours ago. Here's the AFPR gauge now: