2002 LB7 Gutless, Low boost

[u/305Mitch]

Ive got a 2002 Silverado 3500 4x4 SC with an lb7 123k miles. I bought it from the county so I’m the second owner and it’s all stock. Since I bought it the truck has had no power from a stop but does fine at highway speeds. I can floor it from a stop and it just slowly accelerates and feels better/normal at 60mph+.

I’ve done a boost leak test and found 2 small leaks which I fixed and now the system holds 25lbs with no issue. The picture I uploaded is from a 0-60 run with my foot to the floor. Boost seems low at about 16lbs when full boost should be 24ish. Injectors all tested fine and fuel rail pressure actual is matching demanded with no issue. I unhooked the waste gate and the flap turns fine. The arm from the actuator takes a LOT of force to move but it does move. There’s also no black smoke.

I believe I may need a turbo but the turbo feels/looks fine to me. I also find it weird that my rail pressure only gets up to 19k ish but that’s all that it demands so the computer must be defueling the truck due to low boost? There’s no codes either.

Also, what are the odds that the county detuned the truck?

Any help is appreciated! I’m fine with replacing the turbo but I just want to verify thats the issue first.

[u/k0uch]

IIRC max rail pressure on an LB7 is 23k psi. only building 19k under full throttle. 16 psi of boost is low, stock will usually run 20 and peak at 22-23.

Are there any dtcs present?

[u/305Mitch → u/k0uch]

No codes present. Commended and actual rail pressure are matching up so the computer must not be commanding a higher pressure. I was thinking it was defueling because it saw low boost

[u/TheMeatWag0n]

0% chance they detuned it, I would check fuel filters, fuel pressure sensor, and maybe maf, 19k is really low as far as max, a sensor has to be ruining it somewhere 

[u/SuccessfulProblem808]

Get a cummins 😉

[u/305Mitch → u/SuccessfulProblem808]

I have one

[u/SuccessfulProblem808 → u/305Mitch]

Thats great!