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2008 3500HD Dually
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Discussion Starter · #1 ·
Hey Fellas, Well, the rabbit's out of the hat. Picked up a 08 dually with 180K last fall for a great price.

I have learned whenever you haul under medium to heavy load (Round Baler on Deckover, maybe 8k) or 14 haylage bales (4.5 by 4, maybe 16k) the engine goes into a reduced power mode. The dash will show "check/change fuel filter" or "low fuel rail pressure" or "DPF soot build up". The FF was changed just prior to getting truck.

I stopped at a local diesel shop. They said change the Fuel and air filters with genuine GM parts. Then the kid said "how do you drive it?" I said, "I have gray hair." He said, "there's your problem". I said "I know, haven't been laid in 6 months".

Point being is he said I need to drive it like I stole it.

Anyone care to weigh in? I love the truck and it's power, when it's there.

Had another mechanic tell me 08 to 15 were really sucky years for the Duramax. You guys agree?

I have to replace it one point and would consider a new Duramax but not if I have to drive it like a maniac all the time. Some maniac time is good for the soul and I ain't no saint, but....

Comments fellas'. Thanks, Mike
 

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2017 GMC Denali 2500HD, 3.5" Rough Country Lift, 305/55R20 Cooper Rugged Trek, Paragon Bed Cover
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First, the mechanic who said 08 to 15 were "sucky years" probably doesn't work on them as much as he claims. Every year of Duramax has that one thing that makes it "the worst Duramax ever made". It just depends on who you're talking to when they tell you which one is the worst.

The DPF soot build up is definitely a sign that you're probably not driving the truck hard enough. The truck is smart enough that it won't let you over work it, so when you're pulling that 16k lbs, let it rip. It will do its job.

As for the low fuel pressure, you likely have collapsing fuel lines, and that's why it is only showing up when you're working the truck. The fuel system on the 08 is under vacuum from the tank to the high pressure pump, so when those rubber lines coming from the tank get old they tend to collapse under high fuel demand situations.

Your homework assignments:

1) Buy a monitor of some kind for the truck. Edge CTS3, Banks iDash, or one of the bluetooth readers (I can suggest one if you want to go this route). The most popular monitor right now still seems to be the Edge CTS monitors due to the larger screen. The Banks iDash does all the same things, just in a smaller package. Both are great. The monitor will let you read and clear trouble codes and on the 08 you'll be able to see a lot more information about the runtime environment of your truck.

2) Replace rubber fuel lines between the tank and the filter head. NAPA fuel lines work fine.

3) Replace fuel filter again. I know it hasn't been many miles, but I've personally had 2 filters become clogged in less than 2000 miles. It's a cheap part and it helps rule out potential issues.

4) Get the truck hot. Don't baby it, especially when it's doing a regeneration cycle. If you aren't able to tell yet when it's regenerating, you'll notice the truck idling closer to 1000 rpms at stop lights/signs, and a charcoal like smell from the exhaust. When this happens, if you're able, get the truck on the highway and run it like a rented mule for 20 miles or so. The DPF needs to get nice and hot to burn off that soot it has accumulated over the last 200 to 400 miles. The monitors I suggested all have the ability to tell you when you're in regeneration mode, so you'll know you need to drive it a little harder or longer to get it through the cycle.

If after doing all this you're still getting the change fuel filter message, you may have a leaky filter head. It's also a cheap and fairly easy install.

If you're still consistently getting DPF clogged messages, that Edge or Banks monitor will let you do a manual/stationary regeneration. This is going to run your truck REALLY hard in park for 15 to 20 minutes and burn off the junk in the exhaust. You'll need to do it outside, hood open, and make sure that nothing combustible, including dry grass is within like 8 feet of the exhaust pipe. You will start a brush fire if you're not careful.

Good luck, and welcome to the family.
 

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Former GM Tech and parts
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Ok, fuel filter was replaced last fall just before you got it- how many miles has it been? How is the quality of fuel that you run?- hard to know for sure. Start by changing the fuel filter.
Only happens when you are demanding higher pressure and higher flow/volume while you are hauling.... a couple of us were just having this discussion on another thread a couple days ago. I say you need to get someone to run a return rate test on the fuel injectors. It needs to be done at the same conditions when this happens- engine warmed fully and under high demand- I would almost bet your injectors are returning too much fuel and when you have high pressure/high demand they are returning too much fuel and creating the low power under load. I've seen it several times, had two trucks of my own do it.
 

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2017 GMC Denali 2500HD, 3.5" Rough Country Lift, 305/55R20 Cooper Rugged Trek, Paragon Bed Cover
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Ok, fuel filter was replaced last fall just before you got it- how many miles has it been? How is the quality of fuel that you run?- hard to know for sure. Start by changing the fuel filter.
Only happens when you are demanding higher pressure and higher flow/volume while you are hauling.... a couple of us were just having this discussion on another thread a couple days ago. I say you need to get someone to run a return rate test on the fuel injectors. It needs to be done at the same conditions when this happens- engine warmed fully and under high demand- I would almost bet your injectors are returning too much fuel and when you have high pressure/high demand they are returning too much fuel and creating the low power under load. I've seen it several times, had two trucks of my own do it.
I thought maybe injectors too, but I haven't heard of it giving the fuel filter message with injectors, though. And the injectors on the 08's are a lot better than previous generations, so I wouldn't think that at 180k they would be my first stop on the troubleshooting train.
 

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Discussion Starter · #5 ·
First, the mechanic who said 08 to 15 were "sucky years" probably doesn't work on them as much as he claims. Every year of Duramax has that one thing that makes it "the worst Duramax ever made". It just depends on who you're talking to when they tell you which one is the worst.

The DPF soot build up is definitely a sign that you're probably not driving the truck hard enough. The truck is smart enough that it won't let you over work it, so when you're pulling that 16k lbs, let it rip. It will do its job.

As for the low fuel pressure, you likely have collapsing fuel lines, and that's why it is only showing up when you're working the truck. The fuel system on the 08 is under vacuum from the tank to the high pressure pump, so when those rubber lines coming from the tank get old they tend to collapse under high fuel demand situations.

Your homework assignments:

1) Buy a monitor of some kind for the truck. Edge CTS3, Banks iDash, or one of the bluetooth readers (I can suggest one if you want to go this route). The most popular monitor right now still seems to be the Edge CTS monitors due to the larger screen. The Banks iDash does all the same things, just in a smaller package. Both are great. The monitor will let you read and clear trouble codes and on the 08 you'll be able to see a lot more information about the runtime environment of your truck.

2) Replace rubber fuel lines between the tank and the filter head. NAPA fuel lines work fine.

3) Replace fuel filter again. I know it hasn't been many miles, but I've personally had 2 filters become clogged in less than 2000 miles. It's a cheap part and it helps rule out potential issues.

4) Get the truck hot. Don't baby it, especially when it's doing a regeneration cycle. If you aren't able to tell yet when it's regenerating, you'll notice the truck idling closer to 1000 rpms at stop lights/signs, and a charcoal like smell from the exhaust. When this happens, if you're able, get the truck on the highway and run it like a rented mule for 20 miles or so. The DPF needs to get nice and hot to burn off that soot it has accumulated over the last 200 to 400 miles. The monitors I suggested all have the ability to tell you when you're in regeneration mode, so you'll know you need to drive it a little harder or longer to get it through the cycle.

If after doing all this you're still getting the change fuel filter message, you may have a leaky filter head. It's also a cheap and fairly easy install.

If you're still consistently getting DPF clogged messages, that Edge or Banks monitor will let you do a manual/stationary regeneration. This is going to run your truck REALLY hard in park for 15 to 20 minutes and burn off the junk in the exhaust. You'll need to do it outside, hood open, and make sure that nothing combustible, including dry grass is within like 8 feet of the exhaust pipe. You will start a brush fire if you're not careful.

Good luck, and welcome to the family.
Thanks for the reply and welcome Melon.

I will start down the road to figuring this out by replacing the FF and the Air filter for good measure. Replacing the fuel lines sounds good too.

Edge CTS3 monitor sounds like a good idea if it'll let you do your on regen.

I will keep you guys posted on this as it evolves.
 

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Discussion Starter · #6 ·
Ok, fuel filter was replaced last fall just before you got it- how many miles has it been? How is the quality of fuel that you run?- hard to know for sure. Start by changing the fuel filter.
Only happens when you are demanding higher pressure and higher flow/volume while you are hauling.... a couple of us were just having this discussion on another thread a couple days ago. I say you need to get someone to run a return rate test on the fuel injectors. It needs to be done at the same conditions when this happens- engine warmed fully and under high demand- I would almost bet your injectors are returning too much fuel and when you have high pressure/high demand they are returning too much fuel and creating the low power under load. I've seen it several times, had two trucks of my own do it.
Thanks DMAX,
Would the CTS3 Melon mentioned be able to do the injector return rate test?
 

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Discussion Starter · #7 ·
I thought maybe injectors too, but I haven't heard of it giving the fuel filter message with injectors, though. And the injectors on the 08's are a lot better than previous generations, so I wouldn't think that at 180k they would be my first stop on the troubleshooting train.
Speaking of injectors, prior to buying the truck, I brought it to my mechanic. Local guy who works out of a shop at his residence. He is admittedly not a diesel expert, but his son is a complete Duramax fanatic. We looked it over good. It was a fun Sunday. I got the truck for 14K which according to the mech's son was very cheap. We figured there might be something hidden in there but at that price it was still worth it due to it's overall condition.
The previous owner used it to haul boats. BIG Boats. He showed me a pic of what must of been a 40ish foot fountain.

It wasn't showing a check engine light at the time, but when they hooked up their fancy-er tester it did show the low fuel rail pressure... We called a Duramax guy they knew and he started talkin' points similar to what you guys are talking.
 

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Would the CTS3 Melon mentioned be able to do the injector return rate test?
Yes... The Edge Insight CTS3 can also reset the trouble codes since the truck probably threw a P0087 code. "Cheaper" fixes, than replacing the CP3 fuel pump, are installing a lift-pump and for my '07, I shimmed the FPRV valve to "increase" the spring rate of when the valve opens.
 

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Discussion Starter · #9 ·
Yes... The Edge Insight CTS3 can also reset the trouble codes since the truck probably threw a P0087 code. "Cheaper" fixes, than replacing the CP3 fuel pump, are installing a lift-pump and for my '07, I shimmed the FPRV valve to "increase" the spring rate of when the valve opens.
Interesting. Thanks Rob.
 

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Angus Mike the guy above knows his shirt

I had same issue this fixed my 2010 she yanks my 15k 5th wheel over mountains like it's a radio flyer
 

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CTS will not be able to do the return rate test- can show balance rates, but not run a physical return rate test where it actually measures the fuel coming out of the return side of the injectors.
 
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Discussion Starter · #12 ·
Angus Mike the guy above knows his shirt

I had same issue this fixed my 2010 she yanks my 15k 5th wheel over mountains like it's a radio flyer
DDually,

Which guy? What was the final verdict for yours ? Just came from the GM dealer. He seez a farmer in an adjoining town is having the same issue.
 

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Discussion Starter · #13 ·
CTS will not be able to do the return rate test- can show balance rates, but not run a physical return rate test where it actually measures the fuel coming out of the return side of the injectors.
Ten four. Does the DPF have a life span? Just came from the dealer. Talked to the lead mech. He say's he's chasing the same issue with another guy with a LMM. Everyone seems to be talking about similar stuff.
 

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Every filter including DPF's have a lifespan- what is it though is kinda hard to say. For the most part in what we are seeing in my dealership group on our large ag products is averaging say 6000hrs or so. Lots make it farther, some don't make it there. What is it on an LMM or LML truck? I varies vastly in how the truck is used, maintained, how much it idles, how hard it is worked, how many sensor issues it has, def quality on the newer stuff.... SO many things can make a difference
 

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Shoot cant hurt to try that spray in DPF cleaner to help aid with the DPF. Sounds like it gets it back to fresh again (or close to fresh as can). Any idea of your regen mileage? I used get about 300/regen pretty consistently if i recall. About a tank of gas...this was daily driving no load.

Pretty much as stated:
-Fuel Filter
-Filter head? (common as well)
-Collapsing supply line? (seems be more common as of recent as trucks our vintage age..these are up in the engine bay)
-FPRV (prematurely relieving making it unable to build desired pressure)
-CP3 (weak not making the pressure if below checks out)
-Injectors (returning too much fuel yielding low rail pressure)

I drove my truck 1 year with a dpf at 190k with zero issues daily driving it stock as stock can be. No idea its background but from Texas so likely a 5th wheel hauler of some kind.

I know i've been a dmax fanatic about 5 years now but once you know these engines, they are fairly easy to diagnose say, 80% of the time. Those other 20% boy they really make you work for answers ha.
 

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Discussion Starter · #17 ·
Shoot cant hurt to try that spray in DPF cleaner to help aid with the DPF. Sounds like it gets it back to fresh again (or close to fresh as can). Any idea of your regen mileage? I used get about 300/regen pretty consistently if i recall. About a tank of gas...this was daily driving no load.

Pretty much as stated:
-Fuel Filter
-Filter head? (common as well)
-Collapsing supply line? (seems be more common as of recent as trucks our vintage age..these are up in the engine bay)
-FPRV (prematurely relieving making it unable to build desired pressure)
-CP3 (weak not making the pressure if below checks out)
-Injectors (returning too much fuel yielding low rail pressure)

I drove my truck 1 year with a dpf at 190k with zero issues daily driving it stock as stock can be. No idea its background but from Texas so likely a 5th wheel hauler of some kind.

I know i've been a dmax fanatic about 5 years now but once you know these engines, they are fairly easy to diagnose say, 80% of the time. Those other 20% boy they really make you work for answers ha.
Thanks Goat.

The only thing that makes this tricky is in order for it to F up, it needs a fairly decent load hooked up. Last time it did it was Saturday, 16K in haylage bales on a hay wagon (i.e. no electric brakes) 2 miles almost all up hill. On a 15% grade. And, just discovered the e brake cable was broke. Hmmmm. Coulda been interesting if the engine died.... Replacing the e brake cable tonight...
 

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Discussion Starter · #18 ·
Update: Changed air and fuel filters. Hauled small excavator up same hill I had problems with haywagon on with no issues. About 12K. I didn't hammer down, just tried to maintain 35mph.

It's a good sign, but I don't think I am out of the woods yet.
 

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Engine RPM vs speed vs engine load can play a large part in keeping P0087 away. I usually end up in 4th gear, sometimes 3rd if I think it is beneficial, pulling a hill of size, rpm's 2400-3000, and keeping the speed down, tow-haul engaged, gears manually shifted. Lots of people say just to let the Allison decide on when and how to shift - I DON'T, not when pulling hills.
 
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