Shimmed FPR, but no change in pressure

[firemediceric]

A little history: A few years ago I put a vacuum guage on the fuel line before the fuel pump and found I had an obstruction on the fuel pick up. Hutch mod took care of that . I then put a pressure guage on the fuel filter bowl and found I had a pressure reading of only a little over 40 PSI. I tried cleaning the FPR and the screen on the side of the fuel bowl and changing the fuel filter, but long story short, the pressure never went much higher. I moved the guage to where I could see it while driving. The pressure fluctuates between 40-50 both at idle and while driving conservatively. If I really get on the throttle or when going up an incline, especially pulling a load, it's not uncommon to see the pressure guage drop to around 30 PSI and to feel the truck hesitate just ever so slightly.

I consulted two diesel mechanics who specialize in PSDs and they both felt the fuel pump may be going, but they both suggested I wait until a "real" problem surfaces. They said 50-55 PSI is spec, but once again, wait until there is a real drivability issue. Neither of them seemed to indicate that the low fuel pressure would cause any problem.

That leads me to a recent post I saw (I can't find it for the life of me now) where a member said the Ford dealer told him his injectors were shot due to low fuel pressure causing the injectors to burn themeselves up. Reading that got me motivated to try and remedy the fuel pressure issue, which led me to doing the FPR shim. I had plenty of BBs lying around, I didn't need to do any machining to them, so I used a BB to do the shim, but no change. The pressure stayed the same at 40-50, and dropping when I get on the throttle. Figuring it could be the fuel pump just dying a slow death, I replaced it with a new OEM pump. Still, no change! The pressure rose maybe 2 PSI, but not enough to call the problem "fixed."

What else would control the pressure reading I am seeing at the fuel filter bowl?

[tbpower]

I don't know what kind of fuel or setup you are running. Your fuel pressure does not seem that low but with shim it is weird it did not increase. Maybe try by-passing your pre-pump filter if you have that. The only other thing I could think of is to replace you FPR. I heard the BB shim was a little too much around 100 psi? I think you can also get a rebuild kit for the FPR.

[losfinch]

You can always install an aftermarket fuel pressure regulator. "T" both the rear driver's head fuel test port outlet with the front passenger's port into a regulator (like Aeromotives A10006) and then run that into the fuel return line going back to the tank. You'll have to either cap off the factory fuel bowl outlet or shim up super high the spring in there so that the pressure is only controlled/released by the aftermarket regulator. Hope that makes sense. Dino Fuel Alternatives has got a regulated return for $200 that has it all if you don't want to run around getting parts, etc.