Lift pump failure?

[GAmes]

Has anyone had a lift pump totally fail? What are the symptoms? Here is my problem. I replaced my lift pump as preventative maintenance. The old one had nearly 300k and I was anticipating a lot of summer driving. I immediately had intermittant starting problems. I tightened the fuel lines into the pump. I removed the fuel heater. I replaced the elbow from the pump to the prefilter even though it wasn't very old. Every once in a while I still had to manually pump up the pressure to get the engine to start, other times no problem. I returned home a couple days ago, shut down, spent 20 minutes in the house then went out to move the truck. No start until a LOT of manual pumping. This morning the same thing. Got it started, then shut it off. 20 minutes later, same thing. I replaced my rubber fuel lines even though they were only 2 yrs old. 30 minutes later, no start. I am tempted to reinstall the old pump but really don't want to go thru that hassle unless there is a good chance that the new one (made in China, bought from Cummins) is bad. Any ideas?