I have searched the Truckers Report and every other site I could find, trying to identify this problem. So going to post it here and see if any one else has had it and what they did to fix it. Specs. 1999 Freightliner Classic XL. 12.7 Detroit DDEC IV. Super 10. 3.70 rears. not that those have any bearing on the problem. But here it is. I bought this truck and it has a Detroit Reman in it. Around 250,000 on it. I don't have a mechanical boost gauge. I installed a ScanGauge D. It has a readout for the boost pressure. This is where I first noticed the problem. The first load I was grossing 78,000. Truck runs beautiful. No miss, no hesitation, no black smoke, no check engine light. And NO POWER! The boost gauge on the Scangauge said it was only building around 17 psi. The guy I bought it from said it was a 500. I decided he was full of $it! So, here is what I have done up to this point. Took the truck to my local shop. Yes they are trustworthy. Plugged it in no codes to speak of. So I pressure tested the Air to Air system. Tests fine, will hold 30 psi for 5 minutes. Checked fuel pressure, it is within specs. Changed the MAP sensor, otherwise known as the boost pressure sensor. still no change. So took it to a computer specialist. Found out the engine is a MK and had a 430/470 BK ECM on it. Reflashed it with the correct program for the MK, a straight 470 HP program. Then had it turned up around 10 percent. After all that I now see up to 25 psi of boost pressure. Oh I need to add, replaced the old Garrett wastegate turbo with a new Borg Warner non wastegate turbo. It pulls fairly well, now. But this is the deal. Even if the ECM was a still set at 470 it should at a minimum built 28 psi of manifold pressure. With the bigger turbo and the ECM turned up I should see closer to 35 psi. I think it's an electrical problem, a sensor somewhere. But I can't find anyone that can give me the details of how the computer determines when to cut the fuel back. What I mean is this. The truck will take off and act like it's going to really pull, but when it hits about 25-26 psi of manifold pressure, it stops like something told the ECM to back off. It will stay at that level and and pull fine, my EGTs aren't high, temperature stays fine, etc. Again, No check engine light. No miss, no smoke, everything seems to be working perfect. It just wont seem to finish the job. Something is telling it to back off. Again, It's not running out of fuel. Something is making it back off. Hope this makes some kind of sense to someone.
Detroit 12.7 DDEC 4 Interesting problem
Discussion in 'Trucks [ Eighteen Wheelers ]' started by eagle005, Feb 10, 2015.
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Did they go into parameters and check things out ... Could have something a company set up in it like progressive shifting or torque limiting etc there's two sides to ecm you fixed the horsepower side but may have to tweak parameter side .. Just a thought
jamespmack Thanks this. -
Possible power trim protection did anyone try to check the injector and valve adjustment making sure that everything is set up properly mechanical u have spent some serious money already u can change to whole sensor harness in the old Detroit and it should even be that expensive that might be a possible thought given that detour does have wiring issues
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Considering the entire ECM was reflashed, I don't think it's a parameter problem. Now I don't claim to understand everything about the ECM, it's just that I am assuming when one does a total reflash it resets everything including parameters. This is what has me scratching my head, Ok, with the original 430/470 program installed, I could get around 17 psi of manifold pressure. Now with the new program, I can get up to 26 psi. Ok, but it still acts the same way. Really hard to figure out a way to write it down. LOL. It's like when you're taking off you had a wastegate on the turbo, and all I have done is changed the point where the wastegate opens. Does that make sense??? Because it pulls hard till it hits a certain point and then just stays there. It won't pull any better. With everything I've done I have tremendously increased the performance, but it still isn't right. I guess that's what is bothering me. I have not had an overhead run yet. That's the next step. But if the valves were that far off it doesn't seem like it would run and idle as smooth as it does.
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Eagle005 where are you from/where do you run? You would be wise to have the overhead run, though I'd be surprised if that's your issue.
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had a similar issue with a 12.7 i bought back in 07 up untill last month the truck would run like it was being held back turned out to be a bad engine harness . i have changed boost sensors and truck still had no power i ended up swapping in a used engine harness i had off another motor i had and the truck ran way better i'm about to order a new engine harness as-well as vehicle harness(ecm to cab)
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I live in Western Kentucky. I'm going to run the overhead this weekend. See what that does. I don't think it's the problem. But it can't hurt. I've talked to a number of shops that I know and trust, and they all just scratch their heads. I won't say that a new wiring harness won't fix it, but I would think that if that was the problem I would be getting at least a check engine light. I wish I knew where to find a description of how the engine controls work. As in, which sensor tells the computer when to pour the fuel to it and so forth. But it seems that everyone is just a parts changer these days. No one really knows or cares how stuff actually works.
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@truckerbangin. Did you get any codes at all with your issue? Or did it run basically fine, and just felt like it was holding back?
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Blown intake gasket?
Oldironfan and jamespmack Thank this. -
. They specialize in pre-emission engines, and definitely get into the internals of the ECM. I've been very satisfied with the work they've done on my truck.
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