LB7 low RPM "bog"

[Luvss350]

So It didn't do it before, and now it's randomly dying....

Fix whatever you screwed up while doing the Headgaskets and injectors! Why would the pump just magically go bad?

This fits right in with the "built not bought" thread going on right now. And is a prime example that some things are better left to professionals.


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I know you are probly not trying to be an ass but between my dad and I we have +50 years of experiance between us how much more professional experiance do we need to do a simple head gasket and injectors job?


1 truck sat for 6 monts
2 fuel could have gelled up in the pump
3 shit brake when not in use
So no its not magic

 

[DAVe3283]

So I see no problem wanting to fix your own truck. But the answer to the questions is a data log, not speculation. If the CP3 is failing, it will show as a fuel pressure issue in the log. No need to throw parts at the truck, let's get the log and start diagnosing, not guessing.

More likely than the CP3 failing, is air getting in from a failing filter head or bad rubber fuel line, both of which would have been disturbed during a head gasket job. It is also possible the injectors got debris in them during the repairs, and now the injectors are shot.

But again, we need a log to see what's happening. No need to rush out and buy parts yet.

If you can get a log of it dying, and one of a hard start, those would be extremely helpful.

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[bmc1025]

Install a clear piece of line after the fuel filter housing you can use a hose barb to connect to the existing line. Check for air bubbles. If no air bubbles while running you can pretty much rule out the fuel system from the tank up to the filter head

 

[Luvss350]

So I see no problem wanting to fix your own truck. But the answer to the questions is a data log, not speculation. If the CP3 is failing, it will show as a fuel pressure issue in the log. No need to throw parts at the truck, let's get the log and start diagnosing, not guessing.

More likely than the CP3 failing, is air getting in from a failing filter head or bad rubber fuel line, both of which would have been disturbed during a head gasket job. It is also possible the injectors got debris in them during the repairs, and now the injectors are shot.

But again, we need a log to see what's happening. No need to rush out and buy parts yet.

If you can get a log of it dying, and one of a hard start, those would be extremely helpful.

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Ok thank you i will try today to get the log i just havnt had time yet. I was just at work thinking and thought i would ask

 

[IOWA LLY]

I know you are probly not trying to be an ass but between my dad and I we have +50 years of experiance between us how much more professional experiance do we need to do a simple head gasket and injectors job?


1 truck sat for 6 monts
2 fuel could have gelled up in the pump
3 shit brake when not in use
So no its not magic

So fix it then.

The maf made sense at first. Now you add completely new problems. You don't know how to log or use a scan tool properly apparently. Both of which are required to be able to properly work on a Duramax.

We are not mind readers! You wouldn't believe how many people in a months time come on here after doing major work to their trucks and then have problems and expect people here to diagnose it magically for them.

You are going to have to provide actual info if you expect us to be able to help.

This does not mean info like "it dies" or, it bogs so I attempted to tune it and it acts different now but still not good. You realize how loaded with potential problems that statement is???

I don't care if you have 1000 years of experience. Modern day vehicles have specific problems and require attention to specific things to diagnose an issue. Only way to figure out what these specific things are doing is by monitoring them with a proper scan tool.


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[Luvss350]

View attachment 04duramax.zip

here is the data log we got truck was idling then we turned it off and it would not start we tried 3 times and the fuel rail psi stayed around 200
we cycled the key off then on and it stared. we then went down the road and it bogged a little then we poled over and got it to bog again

 

[IOWA LLY]

That log doesn't have all the necessary info.

Need throttle position, MM3 Main rate, and VSS would be nice. Also need fuel pressure ma if you want to fix your rail pressure issues.

Only thing I can say from that log is, your rail pressure was to high at times, but never showed signs of dropping below desired. So I don't think your dieing and hard start issue is related to rail pressure. Could still be fuel supply related...... But I definitely don't believe your pump is bad.

Assuming your B0751 and B0752 tables stock I also don't believe your MAF is causing the "bog" either. But without you logging mainrate so we can see if your against the limiter, or throttle postition to see when your sticking your foot in it it's impossible to tell.