Thanks again for all your replies! It was definitely a shot lift pump. We installed the new FASS DDRP pump and it rocks. I am amazed at how quiet it runs. The FP gauge is also awesome and thanks to MoparMan for posting video footage of a properly set snubber valve! Mine is open less than an 1/8th of a turn and like Mikes the needle rises gently to 21 psi at idle and drops to 14 psi at WOT. I got the IssPro Tranny, Pyro, and FP gauges in the pillar pod and a 2" hole saw made a nice spot to the left of the ashtray for my Boost gauge. I will post pics of the setup.Next project is to repair my QUAD XZT+. The mice ate through the electrical wiring this winter as I must have left it in the way of their nest building plans!

Becareful... Stock lift pump is only 35 GPH and the FSS DDRP is only 45 GPH so you really don't have much for extra volume. This is way you see the abnormal pressure fall. Anything more than 2-3 PSI fall from idle to WOT is a problem...

DDRP should be a good pump for you if you don't have too many fueling mods. Like mike said its only a little more fuel than stock, but enough to keep the pressure in the green. The drop is from demand, but I think normal and acceptable.

I don't put my foot into it very often. I got the Quad XZT+ only because when I pull my trailer the truck is a bit of a dog, otherwise I would've left it totally stock. I wonder how many people that complain about the FASS DDRP may actually have reduced pressure because of a plugged filter screen in the inlet banjo bolt. It is very small!!

Arcwelder

--- Update to the previous post...

Becareful... Stock lift pump is only 35 GPH and the FSS DDRP is only 45 GPH so you really don't have much for extra volume. This is way you see the abnormal pressure fall. Anything more than 2-3 PSI fall from idle to WOT is a problem...

Mike, are you saying that if I keep the fuel pressure around 17 lbs or so I will have enough pressure and volume for cooling?

Have you ever heard of Blue Chip Diesel? Thats where I bought my FASS DDRP. Its been a long time since I've been to his site but I think he says 5 lbs of fuel pressure is enough for adequate cooling of the IP.

Its been a long time since I've been to his site but I think he says 5 lbs of fuel pressure is enough for adequate cooling of the IP.

Blue Chip Diesel Performance proved in 1999 that 5 PSI, under load, made all the horsepower the VP44 pump could make, even with stock fuel lines, fittings and supply pump.

Actually his page state that 5 PSI of fuel pressure is enough to make MAX horsepower... There is nothing stated about cooling or lubing purpose or longivity of the VP44...

If you pump fuel through the same size line at 15 PSI, more fuel should flow and therefore offer more cooling, right??? So, let’s try using 15 PSI or so

Even he admits that 15 PSI is best for longevity and keeps the VP44 cooled the best...

There is a difference between trying to make maximum horsepower for 1/4 mile race and trying to make a VP44 last. If your looking to make a VP44 last you need to keep the fuel pressure high enough to keep the overflow valve open. At about 10-11 PSI the Overflow valve is close and cooling of the VP44 is extremely limited. At 14 PSI and above the overflow valve is open and flowing plenty of fuel past the electronics and parts.

Like I know the minimum oil pressure for a Cummins engine is 10 PSI according to the book... Do you think a engine will last its maximum life with weak oil pressure (Cooling and Lubing)? Why do you expect anything different with a VP44 pump that only has diesel fuel to lube and cool it.

The other thing I tend to stick with the design specs of the fuel system from the FSM...

Little more...

http-~~-//www.youtube.com/watch?v=YREpPrMxkHU

Even more information on this... If you do the volume test TSB design by Dodge/Cummins and anything under 8 PSI will fail...

http://mopar.mopar1973man.com/cummins/2ndgen24v/lift-pump-diag/lift-pump-diag.htm