For the Op the 6 and 9 injectors are the same. Rj no the 02's are not hooked up

 

Ops sorry I missed that.

 

I have the pcm to run in open loop, so the o2s wouldnt do anything anyway.

The plugs were not wet, just very sooted (see first post).

We confirmed the injectors are 5.3, lq4, lq9 injectors.

When it was sort of ideling I could turn the throttle blade by hand and it made no difference, didnt even make it rev higher. Which tells me either there is a gaping vacuum leak that the additional air from the throttle body opening doesnt even effect it, which short of drilling a huge hole in the top of the intake I dont see how that is possible, or more likely its not an air issue.

We worked on replacing the head gaskets today, but werent able to finish before dark. Crossing our fingers for trying it tomorrow...

 

*fingers crossed*

 

We found out the fuel pump isn't putting our enough pressure. It read 18psi right before it would die. I just got my fuel pump replaced at firestone last year so I'm going to call tomorrow and see if it may still be under warranty.

 

To add some details, the pump will build up to the proper 52psi when its primed, but as soon as the engine is started its like the pump is only going half speed or something because the pressure slowly falls down to the 15-20 range which is why spraying starting fluid into the throttle body keeps it running well....

 

I was right, it was the injector tune.

On a different note, did you try running the pump straight to the battery to test it?

 

No, the injector tune is right. As previously stated, its the fuel pump.

 

Glad you figured it out...was the pump under warranty? If not, I'd get an OEM or Delco unit, the aftermarket pumps out there are bigger pieces of junk than the stockers

 

He talked to the manager at firestone where he had it replaced last year, and they agreed to replace it under warranty, but when he had it towed there they changed their minds since it was after an engine swap.

Are the pumps in the 99 OBS 5.7 vortecs the same as the next years 5.3s?