Here's what you can do to fix this (I just replaced a failing fuel pump with a new one and the check valve went south in a few uses, I now have to key cycle it 4 times after only 5 weeks of use). Buy a good quality check valve, and an fuel pressure regulator. splice the fuel pressure regulator in to the fuel system and put the FPR on the fuel rail side of the check valve (the side that keeps pressure). Adjust it to 50~ PSI and hook up a return line that feeds back to the gas tank. You'll have to splice into the tank, or you could plumb the return line into the rubber filler neck. That's ultimately what's going on in other systems anyways.

 

IDK if this helps or not, but my 2000 WJ fuel system has the FPR in the remote filter and has a return hose back to tank. It seems like the simplest way to cure this problem. Just splice one into the pressure line going forward to the rail.

Also, there is no damper on the rail and it has a schraeder valve on it. (Pressure test port) I can see the fuel rail pressure going high during heat soak after shutdown, especially if you're using cast iron exhaust manifolds like the later CA emission models like mine.