My 2003 GMC duramax loses prime sitting overnight and sometimes in a few hrs.If i park on a slope with the nose down, it usually will start without pumping the primer on the fuel head. I replaced the seals in the filter head and it worked great for 3 days , so i thought that was the problem, but then it was back to the same old thing.
I have a nicktane adapter with a new cat filter. Replaced the fuel lines from the engine back to the tank lines(did not replace the short lines going into the tank).Replaced the lines going from the fuel filter head. Replaced the 2 small low pressure lines under the intake. The truck will usually start right up, run 5 seconds then die. If i prime it with the filter head pump , it will start and run ok. Dont know if its related , but after i prime and start it , it surges slightly while idling, dont notice the surge later in the day after i've run it awhile.Truck has 230k miles, injectors and head gaskets replaced at 168k.
No evidence now of leaks, any ideas on what to try next?, its driving me nuts. been working on this off and on since April.