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Discussion Starter · #1 ·
Hello everybody,

Been trying to diagnose whats up with my lb7, truck is a bone stock 02’ chevy 2500HD it has 250,000kms with the stock exhaust no muffler.

Truck screams at full throttle but feels like its going nowhere. My buddy has two lb7s and both feel way quicker.

Ive replaced the fuel filter twice, air filter, oil change, tranny service, swapped maf sensors with my buddys known good and nothing changed. No boost leaks, just a haze of black smoke at full throttle, wont go over 90kmh uphill and 0 passing power

So im wondering if anybody has any other ideas i can look at? Or does the thing just need a small tune thrown at it? Not sure if i was expecting more out of the lb7 or what. Unsure what to do cause its not making good power. TIA
 

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Always make sure both batteries are fully charged when testing. Have your truck scanned for codes - I suspect that will be some. Don't make any mods until youget your truck fixed in its present configuration. Adding new stuff just confuses things even more.
 

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Compare your desired fuel rail pressure and actual fuel rail pressure when it feels underpowered and see if those numbers match or are pretty close.
 

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Discussion Starter · #4 ·
Compare your desired fuel rail pressure and actual fuel rail pressure when it feels underpowered and see if those numbers match or are pretty close.
Desired rail pressure is at 23k and actual is about 5-8k at 100% load. Ive been told the cp3 is weak but i really dont want to spend the money/do that job if its not the problem.
 

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Desired rail pressure is at 23k and actual is about 5-8k at 100% load. Ive been told the cp3 is weak but i really dont want to spend the money/do that job if its not the problem.
I know the feeling. I bought a lift pump and checked return rates but the only cure was a new cp3. Maybe your issue is different though.
 

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Could check for collapsing fuel lines, but my guess is also CP3. When mine went, however, I did have a CEL - P0093.
 

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It's not that bad of a job & you can buy a reman pump for as little as ~$600. Need to also budget for fresh coolant, and plan on replacing every gasket, o-ring, etc that you have to even touch. I had HELL with the o-ring on the bypass tube where it fits into the thermostat housing. Chevy dealer looked up the part number & still gave me the wrong one. It's kind of thicker & flat on the sides vs. a traditional one.
 

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It's not that bad of a job & you can buy a reman pump for as little as ~$600. Need to also budget for fresh coolant, and plan on replacing every gasket, o-ring, etc that you have to even touch. I had HELL with the o-ring on the bypass tube where it fits into the thermostat housing. Chevy dealer looked up the part number & still gave me the wrong one. It's kind of thicker & flat on the sides vs. a traditional one.
^ experience talking here :)

I also swapped out all those little fuel hoses that go every direction under there that are hard to get to. I didn't want to get back down in there again.
 
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