A couple months ago I had new injectors installed in my '06 6.0. I also installed an AirDog II lift pump/conditioner and regulated return system from Sinister Diesel. The regulator had a mechanical fuel pressure gauge which I set to 70psi. The van ran great, and I felt good about it. Then I replaced the pressure gauge with an electronic sender that would read on my Edge CTS2 in real time while drove. At idle fuel pressure was around 70psi. It would drop to high 50's/low 60's under acceleration and into the 30's under heavy load. My calm was shattered.
I figured it had to be either the regulator or the Airdog pump that wasn't keeping up with the engine. I clamped off the return hose from the regulator, there was no change so I decided the Airdog was at fault. Sure enough, the internet is full of Airdog issues involving low fuel pressure. AirDog even had a rash of motor failures. Had to be it. Spent much time with AirDog on the phone running the tests they asked me to run--I wouldn't want to be paying someone else $100/hour to do all this. They told me I had the revised pump motor and that I had fuel pick-up issues. I was not happy.
$1500 to protect $4000 worth of injectors seemed like a good idea, but I got screwed instead. I pulled the AirDog and reinstalled the stock lift pump. This made the problem worse with fuel pressure dipping into the teens(!) under hard acceleration. They were right, I had fuel pickup issues. I dropped the fuel tank to inspect. It was spotless inside and the pickup screen was clean. None of the fuel lines were kinked, but they were pulled pretty tight which I decided happened when SMB West installed the fuel tank. I don't know if this was causing my pickup problems, or if the small fuel lines were, but I decided to go with a Fass fuel pickup kit. http://www.fassride.com/detail/accessor ... be-kit.php
It has a much larger pickup tube compared to the stock unit:
It also allowed me to use the 1/2" fuel line included with the AirDog II kit. Once the tank was out, the Fass suction tube kit was pretty easy to install:
I also extended the pickup tube for the Espar stuff to within 1/8" of the bottom of the tank hopefully fixing the ongoing pickup problems with that too. SMB had the Espar pickup tube ending well above 1/4 tank. Once it sucks air, you're screwed.
My fuel pickup/low pressure problem is now fixed. I set the fuel pressure to 67psi and it now barely moves under acceleration--I've yet to see below 65psi! As Edd China would say: "Result".
I don't think it's a stretch to say any PSD van has the same pickup issues I had. Certainly any with the (unbaffled) Transfer Flow tank will have the problem. I thought I was golden until I looked hard enough.