The blue wire is a pulsed ground from the PCM.

GM states a minimum of 60psi for proper operation of the fuel system in your truck. I have seen them operate properly at as low as 55psi, but go below that and problems start. Gauge inaccuracies can skew the readings though which is why GM states 60psi, IMHO.

When you tested the fuel pressure, did you observe the pressure after the pump shuts off? You might have replaced the wrong component.

Are there any codes present?

 

ok so the blue wire should have voltage or something i can test with a dmm right?
there are no codes except code 12
the fuel pressure sits at 58 after the fuel pump relay kicks it off and goes down to 56 i think, i got the batt. disconnected right now as im cleaning the ground bolts and screws but ill check for sure tomorrow what the exact fuel pressure is as stated by my maybe not so trusty autozone 50 dollar flippin fuel pressure gauge, i also got another fuel filter to replace the new one thats already on there cuz it might be a bad new one it happens (i get them free anyway).

today i called i autoshop and told him what was going on and he said the first thing he would check would be the catalytic converter, i can see in theroy where it could get pluged as before i fixed the cpi unit and nut kit the first time, it was running waaaay rich, but what i dont get is why would it run sometimes and run good, then die and not start till it wants to.

so tomorrow i will finish cleaning the grounds, recheck fuses, change fuel filter, get a video of the fuel pressure gauge, and try not to blow it sky high.

and Swartlkk didn't notice the F.F.D logo till know and captain sir, im a old volunteer. Knowles Fire Dept. Home of the BIGDOG.

 

To test the injector pulse, you need a tool called a noid light. It plugs into the injector socket and will flash when you turn the engine over. The connectors are known to get weak at the contacts and cause an intermittent loss of fuel being injected into the intake runners, but you just replaced the pigtail harness so that's good.

Your fuel pressure sounds good too. If it holds above 55psi for good period of time, then the fuel system is sealed up pretty good.

How is the O2 sensor & MAP sensor? Both are pretty critical to the operation of the engine in a speed-density engine management scheme such as your truck uses.

I've been a volunteer fire fighter for 7 years now since I settled down. I have been a captain for 2 years. Who knows what next year will bring.

 

i replaced the pigtail comming off the cpi unit and butt connected it to the old plug.then just replugged that into the main harness. are you talking about the plug from the main harness loom that goes across the driver side valve cover and manifold that plugs into the 2 wire red and blue plug, if so i didnt do that one.

have no clue on the map sensor and the o2 sensor, is there a way to test the map sensor?

i joined my dept the day i turned 18, got my back then emt-b before i joined just to make sure id get accepted. when i moved outa state at 22 it was the only thing that almost made me stay....miss it bazillion fold..

 

I posted the MAP sensor resistance readings based on vacuum pressure in another thread... You need an oscilloscope if you want to watch the O2 sensor.

What you replaced is what I was talking about.