I have a 02 duramax with 90,000miles. After sitting over night the truck will not start in the morning , the only way I could get it to start is by pumping the primer several times. This has happened 3 time so far, it does not do it every day it does it about every one or two weeks. The truck is all stock, and runs excellent

Any visible leaks , might be getting air into system , when was last time you changed fuel filter.

No leaks and the fuel filter has about 4k on it. I also had a service engine soon light.