2001 Ram 2500 w 5.9 HO, 6-Speed, external fuel pump - Stock - I had 2-3 times where I had the Dead Pedal issue, so while tinkering I decided to give it more power for towing so here is what I did

• AirDog 150, pulled bed, installed draw straw 1/2 inch from the bottom of the tank, Ran outlet right into VP44. - Removed old filter and pump off the side of the engine and capped.
• Cold Air Intake
• Pulled Turbo Silencer Ring
• Gauges, Oil Temp, Oil Pressure, Coolant Temp, Boost, EGT and Fuel Pressure, Fuel pressure sender is mounted on the Air Dog port, did not use snubber
• Edge Comp for Tuning
• 5" Turbo back straight exhaust

Bled everything and got it fired up, Holy Crap - Sweet! Took it out and found a problem. Fuel Pressure at startup is about 14psi, driving, WOT it would drop 2-3psi then climb back up at idle, exactly what I expected.

2 min into the drive, pressure dives down to about 5psi, WOT down to 0-1psi, WTF, pull over, turn off, restart, back to normal, runs 20 min til back home, thought Air bubble or something like that.

Next Day, same thing normal then pressure dives, once down, pressure does not recover unless I sit with the vehicle off for some time then restart, will not go back up on its own.

First Thought was gauge - ran a T off the airdog, then added a Mechanical Guage in, readings exactly same as the electronic one, so it's not the gauge.

Next Looked at voltage - Solid 13.5v to airdog. Slowly pinched offline to VP44 and pressure climbed as anticipated. For a short term fix, I added two small washers to the AirDog pressure spring and ball, essentially stiffening up the spring, Now pump pushing 20psi at start and then when it drops it goes down to 9-10psi, so at least I am not going to burn up the VP44.

Had a long talk with AirDog Support, Now things get weird. Pull the washers, test - 15psi startup, 4-5 when it drops. Now I hotwire the pump to an external 12v battery, and pump spins up, Check Mech Gauge - pushing 15psi, engine off, and it stays at 15 for 15-20min. Now I start it up, and holy crap, 3 min later... DROP, down to 4 psi. Now that I can hear the pump once I turn the engine off. I can hear it is making a distinctly different noise, a higher pitched whine to it. The pump stays that way until I shut it down and wait 30 seconds to a minute, fire pump, 15psi, pitch lower and sounding like its pushing solid fuel. Talk to AirDog, since we were on an external battery not tied to the truck in any way, They agree to send me a new pump out.

Get a new pump, install pump, fire up... the same thing happening, so it's not the pump. Now really getting frustrated. Start thinking it thru, Maybe it's the return to tank valve, should open up at about 14psi, order valve, replace it, Toss in a new Timbo APPS while I am in there and calibrate it. Fire it up.. No Change - same symptoms.

I am now plum out of ideas, Not getting any codes thrown, truck runs like mad, even at low PSI, not a ton of smoke at any setting but great power. But..... I just don't know.....

Just to clarify, the pressure does not creep down and settle at 4psi, and it literally drops as if someone flipped a switch and the sound on the pump changes to the higher pitch. It stays there until I turn it off and restart, I can put the clutch in and kill it and coast for 30 seconds then restart, and this fixes it about 60% of the time.

Begging for someone smarter than me to help as I am plumb out of ideas, all I know is I can't take my grandkids out camping like this

Thank you in advance - Brian