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there is a common problems with the fuel injectors causing these codes and lack of power
there is a TSB from Chevy on changing out the injectors
click here to view this TSB
I would contact Chevy and see what they can do for you on this
let me know if you need more help
I will open the question to see if any other experts have an idea for you
Hi my name isXXXXX
I under stand from your post that you have already had the injectors replaced, and now are still setting codes that are similar to injector failure codes. correct?
You also mentioned that the fuel filter is hard to get primed.
Does it just feel soft all the time , or when you try to pump it , it sticks down and doesn't return to full up position?
The suction side of the fuel system can cause this if a hose is pinched/kinked. The same exact trouble codes will set because the pump cannot get fuel PIP 4526 bulletin explains this from GM . Check all the rubber lines( cut off the outer foam cover to inspect) .
The most likely one to kink is the hose from the fuel injection control module to the fuel filter inlet on rt side of engine. Check all rubber lines, from tank to engine.
I have seen the pumps do this also, but not have the (hard to prime fuel filter ) concern.
If you can have someone hook up a bidirectional scan tool where they can control fuel pressure. Have them ramp up the pressure to 160 MPA ( 2250 psi )If it reaches this pressure then the pump is not your problem.
Injector replacement is a major job, and things sometimes don't get put back in the correct place. I would concentrate on the rubber lines on top of the engine.
I also assume since you are having a hard time priming the filter that you have already installed a new filter.
Verify there are NO air leaks at the filter housing to. This sounds more like a restriction than an air leak though.
If you need more info, PLEASE ask and i will help.
Did he also check the low pressure side with vacuum gauge? You have to cut open the foam cover over the supply hose to fuel filter to see the rubber hose.
If all the hoses are good. and suction side vacuum is 3 1/2 ". and the injectors have already been replaced, then all thats left is the pump.
A return rate test should be performed just to make sure the new injectors are not returning too much fuel ,resulting in a low fuel pressure reading. 16 ml per bank Max.35-38 API specific gravity 20 ml max 39-42 Ap specific gravity. If that is good then it is definitely the pump.
Fuel filter vacuum should be 3 1/2 "- 4 1/2 " max at idle ,If it is higher then the problem is in your supply side . Fix that first, then recheck the high pressure side max fuel pressure. has to reach 160 MPA. If it can't get the fuel volume to the pump the pump can't build the pressure.(like sucking air, pump cavitates)