I've got a Walbro fuel pump with an inline regulator in the return line set at 29 psi. I run a 12 mic strainer between the pump and fuel tank leading to the stock canister with the 5 mic Baldwin then to a 2 mic Cat then to a Floor It Diesel stage 2 CP3. I use Stanadyne PF at every fill up and truck has close to 92,000 on the clock and shows no codes from the symptoms I am about to describe.

A little history over the last 3-4 months. I have a DiPricol mechanical fuel pressure gauge in the cab. About 4 months ago I started the truck to go somewhere and noticed the pressure only topped out at 22 psi. First thought, filters caught something and are plugged. Changed all 3 filters about a week later and on initial start up the gauge returned to 29 psi. Problem solved, so I thought. On second start up pressure reads around 20 psi. Now I'm thinking fuel pump is failing. I drive the truck in this condition seeing different pressures every time I start it ranging from 11-22 psi. I carry a spare Walbro in the truck waiting for it to crap out as these things are pretty easy to change out on the side of the road. Two weeks ago I pulled into work after my 28 mile drive to get there and as I'm letting the egt's cool down the idle starts to stumble like it's running out of fuel. 8 hrs. later drive it home, runs good no problems. Since it's cold outside I decide to go ahead and install the new pump in my warm garage. I did not replace the filters. Start the truck, pressure rises to 29 psi. Once again problem solved, so I thought. Left for work the next morning pressure rises to around 18 psi. Same small stumble at work as I let er cool down. Leave work only getting 11 psi on the gauge. Get home return Smarty to stock. Runs good for 3 days, no stumble or anything. Yesterday on the way to work, leaving a stop light 1/2 block from work I get a little stumble when taking off. Pull into work parking lot truck just dies and lucky me I coast into an open parking spot.

Rail pressure has been reading between 6,500 and 7,000 at start up and anywhere between 5-6,500 right before I shut it down. I have heard it usually drops a hair when it's cold out. My next move when I get the truck towed home tomorrow is to replace all of the filters and the fuel line and fittings. Maybe something is lodged in there? My pressure gauge is attached via steel braided line right before the CP3. Any thoughts would be appreciated.

 

Maybe check your in-line regulator or the HPRV on the rail for bypassing fuel and not holding proper pressure. Just a thought

 

That's what I find odd. If it was the HPRV I would think I would notice more of a fluctuation in rail pressure. Or at the least, see a code.