You might want to read this which was posted to another forum by a very knowlegable person:
The dealer representative was absolutely correct with respect to the common rail Cummins engines made starting with the 03 model year.
The issue is not the engine, but the fuel system, and even more pointedly - the fuel we have available.
Here is a ditty I posted for a technical discussion regarding relief valve failures on another forum, and it may help you judge the facts:
I have been following your post on trying to sort out a solution to the self-destruction of the Bosch CP3 relief valve, and thought I would send along this reference from Hartridge on the common rail Bosch systems. Page 21 (if you page the same as I do) provides a reasonably accurate depiction of the pressure levels at set rpm's of the CP3 pump. Testing is never done over 1,200 bar, because of excessive cavitation and erosion of the CP3 pistons, but the Cummins uses a total relief setting of 1,585. 85839 bar or 22,994. 824 on the CP3 pump.
http://www.hartridge.com/hl021OM-EN.pdf
I also have included MAN's marine application abstract:
http://www.fsb.hr/sorta2004/abstract/t7-3-man.pdf It also contains very useful data that can be extrapolated to what you are trying to achieve.
The reasons the OEM valve fails in the Dodge application is multiple. 1) The CP3 is designed to never be turned at greater than 2,000 rpm, however its maximum life is achieved at a much lower rpm of 1,200 - which translates to 2,400 engine rpm. As with all things diesel, the life performance mean time to failure is calculated at 80% engine load and speed, and that is significantly fewer rpm's than the Dodge drivers that lean on their throttles achieve. 2) For whatever reason, and I believe it is economics, Bosch does not use a real pressure accumulator, but relies on the rail and the individual injectors' pre-chamber to serve that function. As a result, and this is something with which you are very familiar in your valve experience and hydraulic system experience, the harmonics of multiple pressure releases on a undampened pressure manifold will cause the relief valve to develop a secondary vibration harmonic and set there and pop open and closed thousands of times as it attempts to stabilize the maximum rail pressure. 3) Filthy fuel. North America has the dirtiest diesel of the world. The stuff I buy in Chile is many times cleaner and filtered at 7 microns at the refinery, and has a much higher lubricity factor because it still contains sulfur which cushions the seat in the valve and the seats in the injectors. European standards for diesel are much cleaner than we have in North America at 8 micron purity, and nearly all the diesel over there is true biodiesel with high density polymers created by the type of pressure and temperature refining they use, instead of our quick and dirty alcohol separation method to clean our bio-diesel. 4) A number of folks still insist on installing pulse and width modification fueling boxes on the third generation Cummins, and that is a complete kiss of death to this design. Those modifications will give temporary power gains, but because they are being developed essentially by hackers they do not address the full range of harmonic balance and vibration (feedback) characteristics of the total fuel system, and end up either raising the bar pressure on the rail or by create spikes from pressure waves chasing each other and manifesting themselves into huge temporary pressure waves of up to 1,900 bar and greater.
As a side, I have found that really nothing will solve the dilemma of premature Bosch common rail failures outside of changing the power profile (camshaft) to bring maximum torque back down to usable rpms comparable with the old 12 valve Cummins; by lowering the fuel systems governor cut point to keep the engine rpms below 3,100; and by installing a 10 micron pre-filter and a 5 micron primary fuel filter.
The camshaft and torque curve modification raises major emission problems for the Cummins, but will make the system last comparable to what the guys with the VP44's could expect if they kept their fuel clean and available to the system.