Dodge deisel injection pump problem

I own a 2001 Dodge deisel 2500 cummings. Factory specs still installed and at 80K had the dealer install a new lift pump and injector pump (under warranty) Now, at 125K I have replaced the lift pump do to cummings telling me I had no pressure, and upon changing it and noticing I still had no power, they rechecked and said the injection pump was out as well.

Q: What is the cause of these items going out twice? I hate to have it repaired just to have it go back after a few thousand miles again.
And, at the cummings dealer quoting me $1300 for parts and another $200 for installation, is there anywhere I can purchase a rebuilt or used injection pump to help save $$..

Nobody counts on a vehicle breaking down, or saves for that day either. So, if anyone knows of a used, or cheaper rebuilt---Please Email me @
mbqc@totalspeed.net

Thanks for a great site!

-Tracy Mason
Denver, Colorado