Almost starts

Many thanks for the help. I will try suggested repair and have ordered suspected defective part in case the connections and other components check out okay.

Joe finally got the opportunity to replace the suspect part - ignition module. Started right off, I'm jazzed. Hope this is the cure since there can be so many other causes for difficulty starting. Thank you so very much for your help!

Well shoot, I spoke too soon, I guess. When it fired right up after module repair, I was certain that was the fix. After it set overnight and getting ready to leave for work today - same thing again. Crank, crank, and more crank, no start. I got it started finally this afternoon. I'm thinking I'm losing fuel pressure after sitting for an extended period. Once it did start, it would still start up right off after letting it sit for 10-15 minutes. Sound like a pressure scenario, or pump not working correctly? It runs so it must be working to some reasonable amount but maybe not enough to maintain system pressure?

Joe, I was able to try the 5x key switch method today. When starting (6th try) it fired briefly then cranked for about 10 seconds before firing in a chug-chug-chug manner and then starting. ( Try to imagine Humphrey Bogart kicking the boiler on the African Queen to get it going) kind of like that - sort of. But it did start and idle normally afterward and I let it run for a few minutes to see if it might kick a "check engine code" but nothing showed. I shut down and waited a few minutes and tried again - started as if nothing was wrong. I checked my fuel rail and there is no service port for testing fuel pressure. My Chilton's svc. Manual says to make a tee fitting using fuel lines and connect to fuel line(s) before the filter to test fuel pressure. Thanks for your input on this - i'm getting a baptism by fire (not literally, I hope) in troubleshooting this problem. The book has some specifics on it but it seems to be more detailed on the 6 cyl. Engine and I'm working on the 4 cyl 2.2l.

Was finally able to find the test port at end of fuel rail. Checked 45 PSI with key "on"- up to 57 PSI when running. Obd2 showed two codes - P140/P143 bank 1 sensor 1 (upstream)- replaced both up and downstream sensors. Same symptoms exist - extended cranking time to finally start and noticeable odor of gas thereafter. Once running, seems fine. Am leaning toward possible injector malfunction/leak. Have you ever encountered this problem before?

Rechecked fuel pressure today. Key on @ 50psi. Held for a moment and began to drop about 1 psi every 10 secs. Key off- purged pressure and rechecked - 48 psi, held that for a moment and began to drop at about same rate as before. Seemed to hold steady around 40 psi or so. Started and reading was 61 psi. And held during entire run sequence( 3-4 min.). Shut off and dropped slowly about 1-2 psi every 10-15 seconds and held at around 45. I was unable to hear fuel pump running during key on mode due to the chimes going off every time the key is switched "on". Once they quit, I did not hear that familiar "hum" of the pump. Does it cycle to a certain pressure and then pause until pressure is needed again(as in starting sequence?). It must be functioning or the truck would not start and/or run. But, functioning to it's proper specification - that I am uncertain of. Unable to find shut-off adapter as yet and any one listed online is kind of high priced for me at the moment. There is no pressure regulator on the fuel rail - only the bleed off/check gauge valve at end of rail and the 4 ports for the injectors ( which I replaced last weekend). My understanding - not confirmed though - is that the fuel pump has the regulator built in to the mechanism on this model. I last changed the fuel pump about 7-8 yrs previous after it failed completely - no start at all - and after that repair until recently, it has worked without fail. Sorry for the long-winded description but wanted to be certain I included all available info for you to work with. I will keep checking for that shut-off adapter, but I'm hoping it isn't needed. The truck does start, it just cranks longer than usual before it fires up. 5-10 secs as opposed to 1-2 secs. Previously.

No, it's configuration is similar, but the relief/test port is at the rear of the rail past #4 injector. - Not on the bend leading back to and ahead of the injector ports #1 through 4 respectively. There is no press. Reg. Fitting or bracket to mount upon on the rail. Per the graphic you provided, the bend being the incoming end/fuel inlet, goes back to injector(s) #1, 2, 3, 4 and then the test port past injector #4. That is where the rail ends. Remove items 1, 2, 3, and the mounting bracket. Items 6 and 7, the Schrader valve, cap and port are at end past injector #4. The injectors I replaced were Delphi brand, not AC/Delco which I installed. I know Delphi has some affiliation with GM, but it seems unlikely that they were not original equipment. And I suspect they weren't the cause but I changed anyway to eliminate them as a possible failure scenario later--since truck is at 210,000 miles. Btw just wanted to say thanks again for your time on this, it is appreciated, as vexing as this problem is/has been. Is it possible GM had 2 (or more?) Different designs for this system? I saw a YouTube video after doing a search for "2000 GMC Sonoma 2.2l flex fuel rail repair" or something similar to that, and the guy in the video had an identical set up as mine. Used his video as reference for r&r of my rail.

Sorry about that. I guess I did not specify that in my previous posts (f/f system). So, likely the pressure drops off sounds like a pending or potential pump failure. One of those symptoms that won't be as apparent until complete failure - at which time it should be obvious. So, I'll start shopping fuel pumps to be prepared for the possible/inevitable likelihood of pump failure. FYI - after the previous pump replacement years back, I tried to think ahead, and cut an access panel in truck bed and riveted a hinge onto cut out panel for "easier" access if needed. So at least in the event of replacement, won't need to drop tank or lift up bed. Hopefully, unless some new developments occur, this should close our dialogue with regard to hesitant start symptoms - if you come across others with like problems let me know if they used different techniques to solve their problems or use my methods as reference - as unorthodox as they may have been. Thank you for all your help and God bless.
Ps. I found that you tube vid and the guy doing it went under the monicker of Lost Socket Motorsports. The video in question referred to "fuel injector change on 2003 S10, fixing a hard start".