Hey all, sorry if the title isn't very clear on what my issue is (only so many characters) so I'll go into more detail here.

I've got a 2012 Silverado 3500HD 6.0L that has be stumped. When I do what I would call a true cold start (i.e engine cold, outside temps below ~ 60 deg.), my truck fires up no problems. If temps are higher than that, even if the engine is cold, I get an extended crank. Sometimes it'll fire up and bog down (which I know can mean an excess amount of fuel trying to burn all at once) but will come out of it after a few seconds other times it'll idle beautifully. I work in Auto parts and I know the test before you throw parts at mantra so I'm doing my due diligence here and trying to figure out common things that will cause that.

Moving on to what I know for sure other than what I've mentioned above:
CEL is on, giving me a purge valve code, I believe saying high flow during non-purge (I have a print out somewhere, this is me guessing). Putting fuel in the tank(s) has no affect (which blows me away) No other codes
I haven't had a chance to do a FPT (fuel pressure test) on it yet so I don't know what the values are.
Battery tests good, although is due for replacement at some point soon.

If y'all have any ideas that'd be amazing. This has been happening for a couple months now and it's getting annoying plus I don't want to have to replace other things like my starter and battery sooner than I have to.

 

Update: Did the FPT this morning,
42 psi ign on, eng off
24 psi idle

Asked a few guys at work, looked at a few documents on my truck and that's low according to the info I found so got a new pump coming. If the issue persists I'll come visit again