I have a 2003 GMC sierra with now approx 164,000 klm. The issue I am having is that when the unit is cold, say, sitting overnight, it starts quite nicely. Only takes a few turns over beforeit flashing up. The problem starts once you have driven a few miles, example of going to the store, shut it off, enter the store for a few minutes, then return to restart. It takes way too long cranking before it flashes up. I am a HD mechainc by trade and have worked with diesel engines all my life. This long cranking is not normal. I dont know exactly how the system functions, and have had the truck to the dealer on four different occasions now. The first trip, they told me there was nothing really wrong with it. just changed fuel filter($67), the second time(300klm later) they contributed the issue to running winter fuel during the summer months. Changed the fuel filter again.($67) I dont agree with that issue of the problem being winter fuel. The third time they even removed the glowplugs and did a leakdown on the injectors, not finding a lot of iussue there. The last trip they say that #8 injector is leaking off the pressure in the common rail, enough that that it  is loosing the prime for startup, and as a result, one has to crank long enough to build up the prime again before it will flash up. Last week it let me down totally. When I returned from the store, it would not start even after considerable cranking. I eventually left it for about an hour, to let it cool off completely, came back and it started as usual morning cold start does. It appears to me that there should be some kind of checkvalve to hold the prime in the common rail. If there is enough leakage in one injector I would think that there should be some fuel dilation in the oil.
Open for any feedback.
Thanks
Don
root0218@yahoo.com