I've been having intermittent starting issues with my 2003 GMC Sierra, apparently relating to the fuel filter. I replaced it not long ago because it was acting like it was clogged, even though it only had 10K miles on it. It worked fine for awhile, then starting having starting issues again, especially when it was hot, sometimes stalling out at idle. It would improve if I pumped the manual primer on the fuel filter, it would start again, and run as long as I kept the rpm up. Then yesterday, in an attempt to tighten the bleeder screw because pumping alone wasn't working, it broke (cheap nylon kind). It took awhile and some imagination to get the broken bits outs, but in the process, I'm wondering if I damaged something. I replaced the bleeder screw, and managed to drive it about two miles, though it was quite dodgy, which I thought was just air working it's way out of the system, even though I bled it before I started out. Then it stalled out entirely and I couldn't get it started again, no matter what I did. Had it towed home. This morning, I took out the bleeder screw and looked inside, thinking maybe some plastic bits and gone into it and clogged something, and I noticed that at the bottom of where the screw goes, there's sort of an opening, like a crescent moon shape on one side of the bottom of the housing. I'm wondering if maybe I punched a hole in there when I was trying to fish out the old screw, or if that opening at the bottom is normal? Any other clues to my problem would be helpful. I'm pretty sure the fuel pump is fine, because I do hear something running in the engine compartment when I turn the key on, but not back at the fuel tank. It just cranks and cranks and doesn't catch. This is my first diesel and I'm still trying to find my way around. Thanks for any and all help you can give!