LB7: Something is still wrong

[JustinD]

Had been having fuel limiting issues with my 01 chased my tail for 5 or 6 months with tuning, had several guys try to see if they could remedy it but no changes in tuning made a bit of difference, had an engine harness done this past week and no more limiting!!!!! :woott: But now it seems to be down on power and a bit rattly tipping into the throttle, seems like if I go wide open it goes good? It is also very slow to spool the charger, I do remember when I was trying to track down my previous issue, if I bled the fuel system it would be better temporarily. Like it is airbound? My logs show my Main injection fuel flow rate 2 at 126.9 and my pulse width is over 3000, and timing goes to 32.0 I do notice a bit of a gap in actual vs desired rail pressure but nothing like I have seen in a bad CP3 situation anyone have anymore input as to where I can look for this issue?


Here are a couple short logs from yesterday

Thanks guys, I am going crazy just thinking of things it "could" be....:banghead:

 

[JustinD]

Anyone have any input on this??

 

[SmokeShow]

So the new harness seems tohave solved your intermittent power issue, but now you just feel like its lacking in power?

Lacking compared to what? What it used to be or what you think it should feel like?

 

[JRODS*LB7]

I think he had mentioned spool up seemed to take a lil longer

 

[JustinD]

Yes it spools a lot slower, it seems to have a rattle now, but maybe because the turbo is a lot quieter now, it doesn't even feel as good as my stock turbo did, just doesn't have the hammer it had before, but this was happening before I changed my charger it was feeling weak, I thought it was my CP3 so when I changed the turbo I put a reman CP3 and LBZ fpr.


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[juddski88]

Check reluctor wheel...

 

[JRODS*LB7]

Justin check this out about timing and pulse width tony B had mentioned about anything over 28 degrees is a waste and just causes rattles especially on stock motors unless your pulling at 4500 rpm IIRC check it out maybe u got a timing rattle and your pulse width is off. I wish i could help u on this but i havent got efi all fig out yet so.. lol im just telling you what i read
:thumb:
http://www.duramaxdiesels.com/forum/showthread.php?t=38732

 

[JustinD]

Check reluctor wheel...

Checked it Tim, it was tight and no visible damage to it.


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[JustinD]

Could it be my FPRV needs to be shimmed? It feels good if you go really easy with the pedal.


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[JRODS*LB7]

Could it be my FPRV needs to be shimmed? It feels good if you go really easy with the pedal.


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Could be just leaking by a little i welded mine so i wouldnt have to worry about it ever leaking again. I originally was going to shim it but then i thought if the needle or seat is worn the shim mod wont really be 100 % so i said screw it and just welded it! I did notice your fuel pressure dropping a lil bit though.

 

[Burn Down]

If you suspect the relief, you can log it under power and see what the rail pressure is doing what it is being comanded. Or use the V2 and crank the rail at idle.

 

[JRODS*LB7]

If you suspect the relief, you can log it under power and see what the rail pressure is doing what it is being comanded. Or use the V2 and crank the rail at idle.

X2 almost 4got about that!lol

 

[JustinD]

It holds rail pressure at an idle I cranked it uo as far as EFI will let me, 160 mpa. I'm running out of ideas.....

 

[JustinD]

I am going to shim it anyway because it needs to be done, but is it possible to hold rail pressure and still pop that valve open? It is super smooth and shifts awesome when I go real easy with the throttle, even seems to be behaving like you'd expect it to with very light throttle, no rattle and the charger seems to be spooling like it is supposed to under light throttle.

 

[ripmf666]

The lb7 motor as a FPRV just like the lly and lbz motors, except its in a harder to get to location and most of the time its not needed anyway.

The location of the FPRV is located on the fuel junction block in the middle of the valley underneath the metal turbo inlet. The easiest way to get to is it by removing the AC compressor, Thermostat housing and Turbo inlet and you will have a good view of the FPRV.

In the last Picture you can see the return line Tee and Banjo bolt, the Banjo bolt threads into the FPRV. To remove the FPRV undo the 10mm strap holding it in place and hold the FPRV with a 24mm wrench while removing the banjo bolt in the return line Tee with a 19mm wrench.

Here is a pic of it removed

Now to Take it apart you will need a 5mm Allen wrench and a vice, or something comparable.

The contents are spring loaded so be careful when taking the FPRV apart.

 

[ripmf666]

Now What i used to shim them with are two M4 washers i got from ace hardware, they fit perfectly in the cap and they are roughly .030" thick each.

Reassemble everything back together as in the last pic in the post above.

And reinstall the FPRV and get back to driving again.

 

[ripmf666]

This write up was done by 2500HeavyDuty from Diesel bombers i just re saved it all and reposted it for you guys since the link did not works. Saved all pics and info.

 

[JustinD]

:thumb: Thank you.

 

[ripmf666]

Your welcome I knew I had it somewhere lol

 

[JustinD]

Hoping if I try enough things I will stumble upon the issue, I am going to do the shim but I don't think it is it. My logs show it holding rail pressure throughout the run?