Well, due to either age, increased demand, or shear luck, your diaphragm pump has finally bit the bullet. this is EXTREMELY common on fuelling-modified first gens, and should be addressed even if your lift pump hasnt failed... yet. Go down to your local fuel injection shop, and buy yourself a Delphi HFP701 lift pump. It cost me 77.35$, much better than the 398.97 i was quoted by cummins This pump is identical to the HFP702, except that it puts out 13-15 psi rather than the 3-5 psi the HFP702 puts out. I verified this with Delphi as well as NW fuel injection. My truck can verify it too, on a highway pull I can produce 34 pounds of boost with a light haze, the same amount as at WOT off idle. Fuelling at all RPMS is better and the truck seems to have more much grunt than with the stock diaphram pump (mine died..).

Cummins part numbers to complete the install (these MUST be bought through your local cummins dealer):

(1) 3914753, fuel supply tube 56.97$
(2) 3939258, spacer gaskets 8.52$
(1) 3914284, spacer 22.24$
(2) 3963983, sealing washers for fuel line banjo bolt 4.72$
(1) FS1232, fuel filter (not needed but recommended) 17.44$

click me for an AWESOME instructional on how-to swap the pump out. Mine took about 3 hours including test drives.

 

i was going to do this when my pump died but was worried about changes in pressure. there are no downsides to running the increased pressure?

 

Unless you run 16+ you will have absolutely no issues, as well as no downsides. I've been running this setup problem-free with a maxxed pump and 3500 RPMs, and my motor loves it.

 

Unless your running big fuel mods, the 702 has no trouble keeping up. It has more to do with volume than pressure. The reason your pressure drops off is because the lift pump can't supply the volume. The VE pump was designed to run with a 7psi input pressure at idle. The 702 can maintain 3+ at WOT, unless your running big fuel mods of course.