LB7 seems to have little boost

[R-MAX]

Hello all, new member and first time post.

I have a stock 2003 lb7 with a straight exhaust. This is my first duramax and I'm alot on the ignorant side of diesels. I've always thought the truck ran fine but when a friend drove it he said it's lacking in boost. He has a 2002 duramax. I'm not really wanting a hotrod but I pull a lot of trailers, large boat, etc. When driving it blows very little smoke even with load and under a hard pull u can very lightly here turbo, like pulling the boat up the ramp.
So I was wondering if there were simple things to check or is it time to take it to a certified mechanic? Thanks

 

[Aaron@LDS]

Do you have a boost gauge?

 

[R-MAX]

No sir I do not.

 

[turbostang7]

How do you know its low on boost? Is it because you can't hear the turbo?
Does it have the stock intake? What more are done to it?

 

[R-MAX]

It's completely stock except for exhaust. It doesn't have the power that my friends stock 2002 has. I just learned where to put boost guage so I'm pulling it in the shop now

 

[superswamper003]

Ok, let us know what you find!

 

[Aaron@LDS]

If your problem was turbo related or a real boost leak you would see more black smoke from the exhaust. The fact that your not seeing smoke is a good thing. But it also indicates that you have the proper fuel to air ratio. Definitely let us know what your boost readings are, and we will go from there.

 

[Awenta]

Is his truck stock?

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[R-MAX]

Yes truck is all stock with straight pipe

 

[dirtydmax]

Any chance your buddies truck is tuned?Not a good comparison if it is and I couldn't hear my ihi stocker as well so your prob fine.Edit:Could be tuned and he doesn't know.

 

[clrussell]

Check the driver side inter cooler pipe, I've seen multiple with holes rubbed in them. Last one the owner never even knew it until I drove his truck one day. Was extremely low on power and wouldn't build much boost.

Usually it rubs a hole down tword the bottom near the steering box.


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[jwg03]

My lb7 wore a hole on my hot side intercooler pipe at steering gear box. I welded the hole for a quick fix. I order a new pipe from HSP.

 

[TheBac]

Check the driver side inter cooler pipe, I've seen multiple with holes rubbed in them. Last one the owner never even knew it until I drove his truck one day. Was extremely low on power and wouldn't build much boost.

Usually it rubs a hole down tword the bottom near the steering box.


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So common that it should be the first thing these newbies should check.

 

[Awenta]

Yes truck is all stock with straight pipe

Not your truck. Your friends. Just making sure you're comparing apples to apples.

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[R-MAX]

Thanks everyone. I did a pressure check on IC tube and cooler. 20 lbs for 30 minutes with no loss. Not for sure on friends truck as far as he knows it's stock, but who really knows. Cleaned MAF sensor and installed new air filter and fuel filter today. Haven't hooked up boost guage yet, didn't have the right fittings to hook it up. Tomorrow having it scanned to see if any codes have popped up.

 

[Awenta]

Depending what you're scanning it with you can see boost readings

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[R-MAX]

Scanned truck today and pulled a p1094c code.

 

[Awenta]

Check if you're leaking fuel anywhere. When was the fuel filter changed?

What did you scan with? Go for a drive and measure actual vs desired frp

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[Hot COCOAL]

Welcome!
How many miles are on this truck?

Your buddy may be mistaking boost for compression...
Since youre digging into it and looking for potential issues and learning the nature if the Duramax and whatnot, you might just want to do a compression check on the cylinders

If for no other reason than to know the health of the engine


Obviously low comoression would lead to less power being produced and may be what your pal is is feeling through the ol butt dyno

 

[R-MAX]

Ok guys got it scanned and it is popping up a p109 and p109 code. I've done the shim mod on the fprv and removed tank sending unit and cleaned screen which wasn't really clogged. I've checked the fuel lines coming out of filter and they are soft enough I can pinch them shut with thumb and finger. Someone told me that they may be collapsing so I will change those out tomorrow. Desired fuel pressure at idol was 5800 and actual was 5850. Boost was at 28@ 2500. So I'm trying everything but codes keep popping up. I truly do appreciate the help.