Overworked
Another contributing factor is that stock Duramax engines don’t have lift pumps. Lift pumps help supply fuel directly to the injection pump, which then sends it on to the engine. This decreases the amount of work the injection pump has to do, which obviously leads to longer pump life. All that is a long way of saying that the injection pumps on Chevys have to do all the work with worse lubrication. Even a CP3 pump will have a hard time providing the necessary fueling without a little extra help. Without a lift pump, the fuel is under constant suction, which causes undue wear and tear on the pump and the injectors, as well as cavitation. Quick side note: besides being a word that my word processor doesn’t recognize, cavitation is defined as the formation of empty space within a liquid because of a propeller. In layman’s terms, it means air bubbles that show up because of the speed of the fan. It shows up more commonly with boats, where the propeller is the means of propulsion, but the same concept applies to any kind of fan-driven pump.