The factory fuel system on your 5.9L Dodge Cummins consists of your underbed fuel tank, fuel or lift pump, high pressure CP3 injection pump, and electronically controlled injectors. For years, Dodge has had a notorious issue with the lift pumps on our Cummins powered trucks.
One of the main issues is its location. Until 2005, the pumps were mounted on the drivers side of the block behind the fuel filter. The two main issues with this setup were that it absorbed a lot of heat from the block, and that it required the pump to "pull" fuel, as opposed to "push" fuel as it was originally designed to do. In 2005, Dodge began to mount the fuel pump inside of the fuel tank. Doing so has helped tremendously with lift pump failure, however, with any type of engine enhancement, they are still prone to failure. This is why we recommend one of our more reliable fuel pumps from such companies as FASS or Pureflow. These systems are available both as a stand alone pump, as well as with an integrated fuel filter and water/air separator, which will help to prolong pump and injector life by removing any particulate matter and air to prevent cavitation, which the factory system cannot do.