LMM Balance rates

[Big Chris]

What should the balance rates be on an LMM? I've been having change fuel filter messages and occasionally low rail pressure 0087 codes when I run it hard. I have a new shimmed FPRV and a lift pumps btw.

I just logged mine and this is what I came up with. Cyl1: -.28 cyl2:-.94 cyl3:-.98 cyl4:+3.37 cyl5:-.01 cyl6: -.77 cyl7:-.03 cyl8:-.44

Actual rail psi: 18554 desired rail psi 4351

Main injection flow rate: .3mm3

Pilot Injection 39.7 mm3

 

[Big Chris]

Truck has 147k on it

 

[JoshH]

I would be a little concerned about the high rail pressure at idle. Maybe you have a FPR problem.

 

[BLACKMAX1]

My FPRV is plugged and at idle my desired was 4521, commanded was 4545,with timing at -2.2 and pulse at 778 are you sure it was that high?

 

[BLACKMAX1]

balance rates look good though.

sorry over read CYL 4. I think as per GM over 4 is out of spec. I had one injector at 2.6 and did the injector cleaning and it went down to .7.

 

[JoshH]

My FPRV is plugged and at idle my desired was 4521, commanded was 4545,with timing at -2.2 and pulse at 778 are you sure it was that high?

I meant a regulator problem. I'm not sure why I added the V on the end of FPR.

 

[BLACKMAX1]

^yep gotcha

 

[Big Chris]

How often are new FPRV's bad? I replaced it last winter when I started having issues. It was new and shimmed from Kennedy. Put the lift pumps on at the same time. Used to only have issues towing lugging it in 5th or 6th. Now I can make it code getting on it on highway onramps or passing. Havn't been towing much so it hasn't been an issue until lately. I don't run the truck that hard. When I want drive hard I take the LLY.

 

[Big Chris]

Just read your correction Josh. That makes more sense.

 

[JoshH]

I'm sure the FPRV is fine. The high rail pressure at idle tells me you may have a stuck regulator or some other problem with it. If that is the case, it could be causing your low rail pressure because it can't move to allow the pressure to increase with higher fuel demands. Once you figure out why the rail pressure is so high at idle, you can further diagnose the low rail pressure code under power. It very well could be one thing causing both problems.

 

[Big Chris]

I'll log it driving and see what happens.

 

[Big Chris]

Logged it driving and was able to get a change fuel filter message. Ran an 80 hp tow tune.

Desired rail pressure max 26107
Actual max RP. 24762.34

Fuel rail pressure reg commanded max 42%
commanded fuel rail pressure reg. Min 2160mm3 Avg 24598 mm3. Max 131070