2012 gmc issue

[Preacherman]

It is a 2012 gmc Sierra 1500 sle w/5.3l gas engine. I tried to prime it but it did not work.

The maf was replaced w/aa new maf.

 

[Preacherman]

Yes, it runs and idles as it should after a few seconds at cold start. Once the engine is warm the issue is gone.

It did have two codes for bank 1 &2 of being too rich. Those were cleared up once maf was replaced.

 

[Prairie Wings]

Yes, it runs and idles as it should after a few seconds at cold start. Once the engine is warm the issue is gone.

It did have two codes for bank 1 &2 of being too rich. Those were cleared up once maf was replaced.[/

when you get a scanner in it, see if there are any misfires in history, and let me know the fuel trim values both short and long term.( possible intake gasket leakage when cold)
Check coolant sensor for proper ambient temp reading cold.
pull the dipstick and see if it smells of fuel.

In addition to the fuel pump test results. ( checking for proper pressure that holds key off after pump primes, leaking injector, regulator)

In my years 1885-2009 as a gm tech drivability tech I never saw a recently made maf sensor that was intermittently bad or any bad maf sensors on the pickups. But wouldn’t put it past gm to mess up a good thing.
I am assuming that you use 87 octane fuel and that it is fresh. And engine oil is good and clean.
Coolant level is full.

 

[Preacherman]

Yes, fresh oil change, thermostat and coolant.

 

[Glock 40]

Get a cheap scan tool that is bluetooth or wifi compatible and Torqe app or rent a cheap scan tool. First guess would be a bad coolant temp sensor.

https://smile.amazon.com/BAFX-Products-Wireless-Bluetooth-Diagnostic/dp/B005NLQAHS

 

[918evo]

Coolant temp sensor, injectors bleeding while engine off, or blown HG(s) is where I would start. First check coolant temp sensor data and if that's ok. Might pull a plug after no-start condition and see if it's wet with fuel or use a borescope to look for coolant. I would run the injectors dry by removing the fuel pump fuse and let it sit overnight. Put the fuse back in and see if it fires up when cold. If there is a schrader valve, you could just release the fuel pressure.

 

[Preacherman]

Coolant temp sensor, injectors bleeding while engine off, or blown HG(s) is where I would start. First check coolant temp sensor data and if that's ok. Might pull a plug after no-start condition and see if it's wet with fuel or use a borescope to look for coolant. I would run the injectors dry by removing the fuel pump fuse and let it sit overnight. Put the fuse back in and see if it fires up when cold. If there is a schrader valve, you could just release the fuel pressure.

Good start. It was the coolant temp sensor. However the fuel pressure was only 55psi but I did not use thread tape so maybe its actually a little higher.