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Discussion Starter · #1 ·
Still new to my duramax, LB7, that I bought back in like April. Truck has no aftermarket goodies on it, not a daily driver, and is taken care of.... not abused. Friday I drove it to work, because fuel is cheaper in Missouri than Kansas, and I ran into some BIG problems.

Got off work at 3:00 and drove the truck 3 blocks to the station. Filled up, and was on my way.... got to a stop light and stopped....... light's green and started accelerating. Got through the intersection and then another couple hundred feet and then out of nowhere....KNOCK KNOCK KNOCK and smoke just pouring out of the exhaust pipe. I mean, I couldn't even see anything behind me. Whipped it in a parking lot right beside where I was on the street and shut her down as fast as I could. It made, and still does make me sick to my stomach that this even happened. The truck was knocking really loud like a rod or something. It was really weird the way it happened under a normal driving condition.

Called a friend I know from the dealership I deal with, and he said it sounded like injectors, or something on top of the piston. Also asked him to run my VIN to se if the injectors had been changed under the warranty, and they were at 114,000 miles. My truck now has 169,000 miles on it, and ran absolutally fine before this. Crappy part is I had to get tailered home and leave on a vacation trip saturday morning til today, so it has been sitting in the driveway this whole time. Also, my friend at the dealership is out of town til monday, so it will be even longer til I know something.

All I know is that he said the injectors can go bad 25 times within 7yrs 200,000 miles and they'd change 'em 25 times under warranty. Not saying this is going to help me, but I was wondering if any of you guys had anything you think this could be, or something I could check considering it is going to sit at my house at least 5 or 6 more days.


Thanks in advance cause this sucks.
 

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Injectors more than likely but being that it happend shortly after you fueled up it could be bad fuel(dirty, water), dont take this the wrong way but there isnt any way you could have put gas in it is there?
 

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Discussion Starter · #3 ·
yeah, it was diesel, not gas, but the knocking was really darn loud and it sounded like a bad rod would in a gas engine. Also sounded like it was misfiring, chugging like the timing was messed up.????????????
 

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FWIW, I know the trucks make weird noises when there is air in the system...but that wouldn't cause the black smoke. I would say maybe water in the fuel. Did you check your oil after this happened? Hopefully it isn't something serious that costs you big bucks though. Keep us posted.
 

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Yeah, check your oil. If the level is too high or smells like diesel its injectors no doubt. Just be glad its under warranty. Its not cheap to do injectors on an LB7, and its a PITA as well.
 

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Discussion Starter · #6 ·
That kinda reminds me of the fact that the service engineoil light came on friday morning. Oil change has about 3500 miles on it. Oil is a little low on the stick but pretty black. Smells a little like fuel, not very much though. Just checked the fuel and my reciept from the fill station to verify I bought diesel and I did. Check engine light is on, still have not started it, and won't cause I don't need to screw it up worse.

Smoke was gray, dark at first then light, and there was a *&%$ ton of it.

Any more suggestions?
 

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Hi, I'm Earth. Have we met?
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try draining your fuel filter from the drain in the bottom if it into a clear container and see if there is water in it!!

This is kinda a pain to do due to the location of the filter but it would atleast rule out water in the fuel as the problem!
 

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Discussion Starter · #8 ·
Pulled a sample from it last night, from the bottom of the filter, in a clean and clear 20oz. bottle that I cut the top off of. Looked at it today after work, and there are what seem to be a few droplets of water in the bottom of the bottle. .......I guess it's not real good, but I find it hard to believe that a couple of drops of water per 16oz. of diesel could make my pickup act the way it did friday. I'm hoping it's the injectors.

When injectors hang up or go bad, is it a immidiate action, like the way mine were? I did see my MPG's slipping away for a little while, nothing too jurastic. The first time I tracked my MPG's when I bought the truck, I was getting about 20.5 mpg's. Currently was getting around 17.5 - 18.?????????????
 

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Discussion Starter · #9 ·
Brought my pickup to the dealership this afternoon. I guess I'll know what the problem is tommorrow.
 

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It sucks it wasent something easy but lets all hope the daler fixes it up!!!

Let us know if it turns out to be injectors or not!
 

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yah i am really interested because my friend's father had teh same problem
 

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Discussion Starter · #12 ·
Well, got a call from the dealership today. They told me that flow rate out of the injectors was way off. They ordered a set of 8 injectors today and are replacing them under warranty. Hopefully that is all that is wrong, only time will tell though.

Just kinda found it odd that they went out like "bam" that quick. Never really heard of that. I hope it's not a computer problem too, maybe telling the injectors to dump or starve fuel from the cylinders. I don't know, I'll get her fixed though..... but it might cost a ton when it's over with.
 

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lets all pray to the truck gods lol
 

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Discussion Starter · #14 ·
I wish I could LOL.
 

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Discussion Starter · #15 ·
Found out today that the injector flow rate was so far off that it managed to throw the timing off too. Told me that the injectors are changed, but it is still smoking a little bit cause the intake was full of fuel. There is still a little fuel inside of it, which is the cause of the smoke now. It is not nearly close to what it was though, they said they are going to drive it around for a while tommorrow and blow the rest of it out. They told me that the injectors fixed the problems now and there is no bill to pay. Thank God for friends.
 

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I put new injectors in my truck around 8 months ago, that being said I have almost the EXACT same thing happen to me. I have driven a total of 8.2 miles after filling up and noticed when turning the corner that I had NO power and a knock with THICK black smoke. My reciept also shows diesel, and I have a airdog150 on my truck. My thought was boost tube first, got home (less than 1/8 mile from where it started knocking) checked everything I can think of, boost tubes are sealed and hold pressure, checked for water at the airdog150 (none) even reprogrammed computer with my PPE back to factory! Nothing helped same issue. When he is saying bad black smoke it is THICK even at idol! Now my oil dose NOT smell like diesel at all. Any help would a great help thanks!
 

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Identical but 3 to 4 times the smoke (could be my lift pump helping with the smoke)
 

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i had 1 bad injector..you could have a few more. Mine smoked a good bit with a load on engine when it let go.
 

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The knock is identical! Now I guess I need to know what the warranty on GM injectors are when bought as parts, and how to check and know what injector is bad. Looks like I have a LOT of reading to do tonight
 
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