08 LMM 0%fuel filter life / Power derate
 

2008 GMC 3500. 4x4 Sierra. Had the truck a month now every time I hook up to the horse trailer the engine light comes on power derates and it goes to 0% fuel filter life. Has new AC fuel filter and replaced both hoses on filter housing hoses by tranny and on top all look good and not linked. not running any tunes stock exhaust for now. It has a air dog 200 with new filters as well but I have it bypassed and still the same problem. It will also go to 0% filter life at 80MPH when passing with the truck empty but it won't derate unless the trailer is on. After a cool down it will clear and go back to running and clear itself. Stealer ships in area are clueless. Local diesel shops want me to leave it with them. I can fix it just gotta learn these junky systems. I'm really hating this truck. Can't wait till I get my 96 dodge 12 valve fixed from being in a wreck. Any help would be greatly appricated.

the fuel life will drop to 0% if the fuel pressure drops too low or you reach 20k miles.

you are likely dealing with low fuel pressure.may be the fuel pressure sensor or pressure regulator. i would run the air dog as this will help keep any air out of the fuel if there is any leaks.

it may also be the pressure relief valve leaking. see here: http://www.kennedydiesel.com/docs/Sh...Test%20etc.htm

if that all checks out then i would guess it is a bad CP3

Like 2004LB7 said we need to verify what the supply pressure is off the lift pump, and make sure there is no leaks in the fuel system. If everything seems to check properly typically the culprit could be a weak CP3. We want to Verify supply pressure off the Air Dog first. to be sure.

I'm looking at ordering the shim kit for the rail relief plug. And put the air dog back in service and bypass the factory fuel filter and install a fuel pressure gauge.

I would not remove the factory filter unless you are putting another filter in its place. It works as a good backup for when you are changing the lift pump filters. If something was to make it passed the stock on can catch it. It also has the water removal function too

The lift pump pressure should make any restrictions of the extra (factory) filter in line a non factor

Ok. So far I've shimmed the rail relief valve .060 inches ( 3 shims ).
Hooked the air dog 2 back up. At 18 PSI.
Still doing the loss of power due to fuel filter life at 0%.
Is there a strainer screen before the pump mounted on the back of the CP3 ?

Ok. I pulled the bed pulled out the fuel sending unit from tank. Had no trash in it and all hoses and fittings are tight. Put all that back crap back on then pulled the filter head and replaced all the O-rings in it and put it back on. Test drove without the horse trailer and at WOT around 80 MPH it goes to 0% fuel filter life left and then derates power. If you shut down the truck for 5 minutes it will run with full power and after a bit the engine light will go off as well. Appricate all the help I can get.
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Are you running any big tunes when this is happening?

What brand filter are you using?

Do you have any way to monitor fuel pressure while driving?

No tunes. All stock.
AC delco filter on engine and air dog filters on pump.
Has 15 PSI on filter head at all times thruout peoblem. Never looses fuel pressure from air dog
Ran a Manuel gauge with 12 foot of hose into cab for testing.

did you attach the gauge before or after the filter? you need to get a hold of a Tech 2, V2 or another tool that can monitor the high side fuel pressure.

it may be that it is as simple as a kinked hose leading up to the CP3 or as bad as a dead CP3. but because your truck seems to run fin otherwise i would think the CP3 is fine.

thoroughly inspect the lines leading up to the CP3 after where you attached the gauge.

the only other thing i can think of is a bad pressure sensor

Yup I'm going now to get it hooked up to a scanner. It's got to be a sensor not working rite

Any update
 

I was wondering if you had any update on your issue. I also have the same problem when I hook up my LQ horse trailer. Having hell trying to figure it out.

I had the same problem with my 2009. Pulled filter head apart and found it full of rubber fuel line. Removed fuel lines from steel line to engine and found it was coming apart.

same fuel filter/derating issue 08 d-max
 

I've got this same issue driving me crazy on one of our fleet trucks- 08 2500HD with the duramax. 156K miles. We installed the airdog system and did a full dpf delete. Running an H&S Mini Maxx tow tune.

When the truck is pulling heavy (#10K+ trailers) and under hard load (like a climbing a grade), the fuel filter will go from 100% to 0% and if I don't back out of the throttle immediately, it will de-rate. When you clear the code 0087 (fuel rail pressure), filter goes back to 100% and full power stays. If you stay in the throttle when the filter message comes on, it de-rates. Coming back from a job in the mountains I just kept my scanner plugged in and reset it every time the filter would drop to 0%.

There doesn't seem to be any issue with driveability, the truck doesn't stumble, hesitate, misfire, nothing. It just de-rates with little warning. Fuel filter changes don't help- I cut open the engine mounted WIX filter and it was very clean. I've inspected all the fuel lines from the tank to the filter, all good.

I haven't checked fuel pressure at the air dog yet but its brand new so not a suspect. I have a feeling I'm dealing with the fuel pressure sensor acting up. Need to get a scanner on it but its hard to duplicate the condition on demand. Idle is good so I think the FPR is OK.

Ideas? I am tired of throwing money at this thing.

That sounds to me like the fuel rail pressure relief valve. Once you pop that thing it will keep popping and at lower pressures which would obviously drop your fuel pressure out but it comes up as low fuel rail pressure. For me it did anyways. I bought a fuel rail plug from PPE it was like 40 bucks. You pull the relief out and put the plug in.

Wow, is this Justin? Seriously... my diesel shop guy called me yesterday (after this has been on both of our backburners for a few weeks) and said he got me a factory fuel filter delete bowl (since we have the airdog) AND that we should delete that relief valve you just suggested.

We're going to try that next week. Hope it fixes it.

Thanks for the help!

No I'm not Justin lol I know a few people that had these issues with their lmms and most of them were told to buy a lift pump or replace filters or rebuild filter head. That fuel rail pressure release is a known pos on the lmms maybe other duramax too. Once you build enough pressure on the rail it opens and then will only get weaker. My truck like I said popped up a low rail pressure code. Good luck bud.

We've got some miles on this duramax (over 5K now) since i did this fix and it has not thrown any fuel related codes or derated. Fuel rail plug seems to have fixed it (and hopefully this post not jinxed it).