[Knarly]

Hi, I have a 2002 Sonoma 4.3 Vortec & Ext. cab.
I keep getting a p0174 and p0171 codes. Cleared the codes but I saved the freeze frame data. I was trying to find if i had a vacuum leak and the only vacuum hose I could find was the one that connects to the front left fender (in the right of the engine bay) I've been dealing with this for a while now.
Here are some of my symptoms :
-When truck reaches ~150-210, after I turn it off and let it sit for about 5 minutes it won't crank, unless I let it sit for about an hour or I shoot starter fluid down the throttle body, even then it barely wants to crank.
-Earlier today I was on the interstate and it seemed like my transmission or engine was bucking at around ~55mph and every so often between 70-80mph ( although this might be unrelated)
-Low idle speed (500-600RPM) usually idles at about 750-800
-Once every blue moon I might get a misfire (although that might be the plugs)

I recently replaced the fuel filter, plugs & wires (1-2k miles earlier), distributor cap, air filter, and fuel cap.
I know it may be the fuel pump it's just I'm trying to exhaust all my options before I have to do that.
What are some things I should check? and is there a vacuum line diagram or picture i could use to find all of the lines?

ALSO, I do have a scanner with access to live data. What are some points I should look for that could help diagnose this?
On the freeze frame data;
Long term fuel trim B1 ; 25%
Short term fuel trim B1 ; 1%
Long term fuel trim B2 ; 25%
Short term fuel trim B2 ; 1%

I'm not a mechanic by any means so ANY info would be appreciated

 

[oldeerslayer]

When you say it won't "crank" do you mean the starter is not cranking the engine fast enough to start or do you mean it won't actually start running on it's own.
Crank is generally a term used for how fast the starter is turning the motor. Won't crank is caused by weak or dead battery,etc.
Won't FIRE means it is cranking OK, but the fire isn't being lit in the cylinders.
I realize this is just semantics but it helps understand your issue.
The codes you are getting point to the fuel pump which is a known common problem on S10's. You can "borrow" a pressure tester free from AZ or one of the other parts places. Minimum with KOEO (key on engine off) is 60psi and it should hold 55 for 10 minutes.

 

[Knarly]

When you say it won't "crank" do you mean the starter is not cranking the engine fast enough to start or do you mean it won't actually start running on it's own.
Crank is generally a term used for how fast the starter is turning the motor. Won't crank is caused by weak or dead battery,etc.
Won't FIRE means it is cranking OK, but the fire isn't being lit in the cylinders.
I realize this is just semantics but it helps understand your issue.
The codes you are getting point to the fuel pump which is a known common problem on S10's. You can "borrow" a pressure tester free from AZ or one of the other parts places. Minimum with KOEO (key on engine off) is 60psi and it should hold 55 for 10 minutes.

Oh yeah sometimes I forget that cranking is different than starting. So I guess the correct term is it won't fire/start running. It sounds like it's running out of fuel. The pump was replaced by the previous owner probably a year and some change ago, but I'm not sure they put an ACDELCO or Delphi (if they make fuel pumps i believe) I just am not looking forward to either dropping the tank or lifting the bed. I was actually thinking about chopping the bed to make a hatch so it could be easier to mess with. But alright I'm going to try and do that tomorrow and see if I can recreate the problem because sometimes whenever I try to show it to someone the problem doesn't come up.

 

[Rhotpursuit]

It will take you longer to cut a hole and a patch than raise the bed.

 

[Knarly]

It will take you longer to cut a hole and a patch than raise the bed.

Well it would be for future purposes also. Just so I could get down there by myself and work on stuff in the future in case something goes wrong for some odd reason

 

[oldeerslayer]

Cutting a hole is the ghetto way to do it.
I would never buy a truck with a patch over the fuel pump. Especially one as new as 02.
Your choice.

 

[Knarly]

Cutting a hole is the ghetto way to do it.
I would never buy a truck with a patch over the fuel pump. Especially one as new as 02.
Your choice.

Well it would be more of a hatch. Plus the bed needs to be resprayed anyways. There's so much **** to do to this truck it's not even funny.? Well I'm probably just gonna lift the bed and repaint the frame. Surprisingly there's barely any rust considering its at 246,000. I know I should probably search first but it's been racking my brain. What other things should I do with the bed off other than checking and repainting the frame?

 

[Knarly]

Alright update ; just tested KOEO, at 200 degrees F. Fuel pressure is 22 dropped to 20.
Running it's at 34psi. So I guess I answered my own question.

 

[oldeerslayer]

It runs at 34? Never heard of that happening. Didn't think that was possible. Sure that gauge was tight on the schrader valve? Sounds like something wasn't tight.
But you're right about answering your own question if those reading are correct.

 

[Knarly]

Yeah I'm sure it was right. Well atleast to the best of my ability. No hissing or leaks. Had a rag under it to check for that. Yeah it runs surprisingly. But when I first cranked it started to die but I had to give it a little gas to keep it running.