Duramax lmm problems. Help please!

[Bryan Burt]

I've got a stock lmm 2008 crew cab 4x4 duramax 273k miles on it that is showing low fuel rail pressure and also lots of black smoke when you get on it and I figured a lift pump might help the cp3 pump easier making the fuel rail pressure better since it has the mileage on it. I was going to install a ppe shim kit also on the fuel pressure regulator valve.

The injectors seem pretty loud also at normal driving speed especially around 1000-1500 rpms. Like maybe a fuel knock? The oil pressure stays steady at 26-30 psi at idle and 45-50 and 2000 rpms. So I don't think it's an engine knock.

I took it to get checked out for $100.... and the guy said the injectors sound a little loud and his computer showed ok balance rates. His gauge showed 5000psi on the fuel rail also? Is that good? He said it most likely is injector varnish build up and he can run the truck on his special cleaning chemical he mixed for another $100 that would most likely clear it it?

I changed the fuel filter about three times now. And each time i poor diesel clean stuff in the filter to clean the injectors, but no change yet. Still says to replace the filter every time I get on it right after I replace the filter. Fuel mileage seems to be pretty poor also. Just wonder if you might shed some light on the subject. If you don't want to that's fine and I understand.
Thanks
Bryan.

 

[Bonestock]

@273k its probably a good time for new fuel system. A fresh set of sticks, cp3 and a lift pump. Also I would check all hoses on the low psi side of system back to tank & throw in a new fpr valve prefferably shimmed. Good luck these low rail psi problems under load can be hard to pin point but it sounds like your injectors are returning too much fuel back or cp3 is weak. What happens when cp3 psi gets ramped up @ idle? Again @ 273k I would replace the fuel system and move on rather than having a pile of money having someone only try to diagnose this without fixing the problem.

 

[Bryan Burt]

@273k its probably a good time for new fuel system. A fresh set of sticks, cp3 and a lift pump. Also I would check all hoses on the low psi side of system back to tank & throw in a new fpr valve prefferably shimmed. Good luck these low rail psi problems under load can be hard to pin point but it sounds like your injectors are returning too much fuel back or cp3 is weak. What happens when cp3 psi gets ramped up @ idle? Again @ 273k I would replace the fuel system and move on rather than having a pile of money having someone only try to diagnose this without fixing the problem.

I put diesel kleen in it over and over and the injectors got quiet. The low fuel rail and limp mode problem was collapsing fuel lines. So I bought 4 feet of 100r16 hydraulic hose and replaced all rubber lines. Two hoses at the fuel filter, 1 hose by the transmission, and one hose by the brake master cylinder. After I did, my 273k mile LMM will fly no problems. I'm so excited it wasn't injectors or injector pump. I removed the lift pump also. It's all factory now. The black smoking is the DPF. It's worn or cracked. From what I understand it will not hurt anything to drive like that. I'm going to be deleting the dpf here shortly anyways.

 

[DIESELMAFIAPER.LB7]

I put diesel kleen in it over and over and the injectors got quiet. The low fuel rail and limp mode problem was collapsing fuel lines. So I bought 4 feet of 100r16 hydraulic hose and replaced all rubber lines. Two hoses at the fuel filter, 1 hose by the transmission, and one hose by the brake master cylinder. After I did, my 273k mile LMM will fly no problems. I'm so excited it wasn't injectors or injector pump. I removed the lift pump also. It's all factory now. The black smoking is the DPF. It's worn or cracked. From what I understand it will not hurt anything to drive like that. I'm going to be deleting the dpf here shortly anyways.

id still run a fass or airdog better filtration and better fuel to the pump... and id shim the relief valve soon as you deletes

 

[brandon06dmax]

x2 on a lift pump and delete the restrictive stock fuel filter u could also pull your injectors and send them to exergy to be checked if that's a concern maybe even have them bored out a little also there are always lower mileage cp3s for sale that could also be an option

 

[IronDX]

The black smoking is the DPF. It's worn or cracked. From what I understand it will not hurt anything to drive like that. I'm going to be deleting the dpf here shortly anyways.

Also a cracked DPF could cause extra regens.

 

[gmac32]

i would say you have a injector knock. I would do a bottle test on each bank and see if they are returning to much fuel. That doesn't cost anything if you do it yourself. If they are good, move on to the next thing. I know the fuel lines under the driver door can collapse and not allow it to suck up enough fuel

 

[DIESELMAFIAPER.LB7]

He already fixed the fuel lines

 

[Bryan Burt]

The low fuel rail pressure problem is still there. It take much longer of a hard ride to make it happen. So the collapsing fuel line fix helped. I also took my truck to the dealership to be tested for $75. They said it has 1200lb pounds of torque and a hp of 600. So it must have a big tune on it. I've never had one of these so I didn't know. I noticed the other day on a long trip they the injectors would alternate from being loud to quiet to loud to quiet over and over the entire trip. When the injectors get quite the engine surges and comes to life with lots of power then the injectors will get loud again and the truck loses power. I was going to get the dealer to put my truck back to stock, but he said with it black smoking the dpf may be deleted and if it went to stock it would go into limp mode if the dpf was gutted.

The dealer thinks that the ceramic ball inside of my cp3 pump has shattered and parts of the ball went into my fuel rails and injectors. Is this possible and does this sound right? He recommended replacing all the injectors, the fuel rails, and cp3. I can get them to do it all for $6300 if I buy the OEM Bosch injectors from another place. Their injectors are $7500. Or I can get an entire used low mileage engine complete with turbo and fuel system for $5000.

Today I noticed it black smoke at idle a little and heavy on Normal driving. And it made the injector noise to quiet noise again. It's done this before right after I bought the truck. So it comes and goes.

I don't care about having crazy power. I just want stock power, maybe a little more and what ever needs to be done for fuel mileage and long lasting. I want to at least see what my lifted f250 7.3l got. It could get 21mpg, but it was a slug in power.

 

[duramax05blk]

Wrong forum damn tapa talk good luck

 

[04D_MAX]

How do they know it has 600/1200? Did they dyno it?

 

[Bryan Burt]

Idk. They just told me it was 1200 foot pounds of torque. And I looked up what average tune has that much torque and it was 600/1200.

 

[Bryan Burt]

I figured that the noisy injectors to quiet to noisy to quiet might be air getting in the fuel lines. Maybe air bubble are building up and then sucking through the injectors. That would explain random surges and noisy injectors to random quiet injectors I would think. So I went through and tightened all my hose clamps on the new fuel lines I installed. I drove it for 20 mins and it ran like a scalded ape! It may be fixed or it might be doing a random power trip that may go away after a few engine shutdowns and restarts. I have my fingers crossed.

 

[Bryan Burt]

Oh I forgot to say that I didn't see much black smoke this time unless it was 3/4 throttle or more.

 

[Bryan Burt]

id still run a fass or airdog better filtration and better fuel to the pump... and id shim the relief valve soon as you deletes

I did already install the ppe shim kit.

 

[Big Block 88]

Log the tune, perhaps pre injection could be screwy???

It sure as shit isn't stock at those power numbers if it is in deed that high.

Perhaps 4000us tune is in