Hello there I'm new to this forum and Am having a heck of a time diagnosing my truck. First off no codes or check engine light. When then truck sits over night with fuel Preasure gauge on by morning zero fuel Preasure. Turn key on jumps to 50 but still very hard to start. Once started if I shut off zero issues. It's just when it sits for long periods. It don't matter temperature outside cause I tried in heated shop with still same results. I've already threw a $350 fuel pump at it with exact same issue reoccurring. 2010 slt Sierra 5.3litre engine Any help would be greatly appreciated. Thanks a lot.