Long time Lurker, but haven't really posted up much. Anyway, here is what I have going on.
I purchased an '06 F350 CC PSD early last spring. It needed some serious love. If you want to check it out, I covered pretty much everything here:
Project Super Duty
I have put over 10k Miles since I installed the blue spring upgrade kit. Last week, the truck started losing fuel pressure. It used be a solid 65psi at idle and never drop below 58psi @ WOT. It dropped to 50psi at idle/cruising and then steadily down to 35psi over a 30minute drive (I was trying to get home). I figured the filters might have gotten plugged up after some bad fuel, since I had to get fuel at small gas station in the middle of Iowa recently. I swapped the fuel filters, no change... So I ordered a Fuel pump, just the pump and not the whole HFCM. The fuel pressure jumped back up to 55psi, so I thought I was onto something, but after a short drive (15mins) it dropped back down to 40psi. I pulled apart the FPR and checked for cut/damaged o-rings, but everything looked good. I decided to throw in a bb behind the spring to help troubleshoot. After a few cycles of the key, it was up to 60psi. Again, after a short drive and some WOT runs for 5 seconds at a time and it was back down to 40psi. I noticed at WOT it would drop to 20psi sometimes, but sometimes hold at 40psi. If it drops to 20psi and I cut the throttle, it jumps right to 40psi in an instant.
I'm not too sure where to look next. I figured I would drop the tank and see if the pick-up is plugged. Also not sure if there is something that controls voltage to the fuel pump. What voltage should I see at the pump? Any input would be really helpful. I am mechanically inclined, but since I am away from all my tools for a year, I'm not able to due much in-depth diagnosis.
Just as an FYI, I was hoping after all this that there was just something up with my electric Fuel Pressure guage. I installed a mechanical and it reads within 1psi. The fuel system is bone stock.
Thanks in advance!