Results of fuel pressure bleed off confirm slow leak in check valve
Key on, engine off = 62 psi
After 2 seconds drops and holds at 58
Key off drops slowly to 50 psi in 1 minute
5 minutes with key off = 30 psi
My plan is to throw in a new Delphi fuel pump in the next couple of weeks.
This is interesting. The shop where I took mine insisted that it held pressure, but I never saw it myself, nor did I ask them if they tested it like you did. I do seem to recall that 58 number though actually, so I wonder if they stopped there.
They also just had the truck for 4 days and insisted they couldn't duplicate the latest version of this, which is that it doesn't stall completely (at least not when I tried it) but it will long crank and/or sputter after starting. When it did that to me, I let it go to see if it would catch up and it did, but my daughter hits the gas when it sputters and it stays running. At an extreme instance of that, it will throw the P0161 code, but doesn't throw it unless one of those hard start instances happen.
I don't have a fuel pressure tester nor do I know enough of what I'm doing to try it myself! LOL. The mechanic at the above shop, who I actually likes, left that shop as of yesterday so I'm done with them and I'll take it to another shop.
Footnote on this shop - I went over there yesterday and one of the owners was being a jerk about me getting the correct VIN programmed. Kept asking if it had the latest code or something. I told him there wasn't a whole lot to the programming of a 97 Tahoe anyway, but yes. Apparently he was PO'd that I prevented him from soaking me for double what it cost him to farm it out. He wanted to charge me $260 and I found a guy (core part of his business, knew what he was doing!) who drove to my house and did it for $135. Anyway, I eventually ignored the owner and don't really even trust these last 4 days because I think the mechanic was under directions not to "find" the problem because that would mean they had to refund me for replacing my VCM.