Duramax Diesels Forum Truck of the Week
  #16  
Old 09-10-2019, 04:52 PM
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what is your rail pressure vs commanded?
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  #17  
Old 09-10-2019, 04:54 PM
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I wonder if the ecm was tuned for larger injectors and will not run correctly due to now having factory injectors. How have you verified that the ecm is stock?
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Old 09-10-2019, 05:19 PM
Unlimitedauto Unlimitedauto is offline
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Seriously thanks for the help guys,
Sorry I forgot to mention, the ecm is new. When I got the truck it had no ecm so I ordered one pre programmed from all computer resources. I thought maybe the new one was faulty and they sent me another. Still the same issue. I have also swapped the rail psi sensor with a good known sensor and no change. Same with the fprv. I’ve wiggle tested all the connectors relating to fuel components. My actual fuel pressure varies but is over 40 MPa with the desired pressure right there with it. Also the injector flow rates were updated when the injectors were replaced as well as the ecm replacement.
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Old 09-10-2019, 05:59 PM
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Any difference if you unplug the maf? Whats the coolant temp show?
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  #20  
Old 09-10-2019, 06:20 PM
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Haven’t tried the maf sensor. I’ll give it a shot and the coolant temp is accurate. I haven’t ran it up to operating temp yet but it does start out at ambient air temp and will rise accordingly.
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  #21  
Old 09-10-2019, 07:03 PM
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Have you logged or scoped the CKP and CMP sensors?
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  #22  
Old 09-10-2019, 07:41 PM
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Quote:
Originally Posted by juddski88 View Post
Have you logged or scoped the CKP and CMP sensors?

This, and with the motor being in the bed of the truck any chance the reluctor wheel was damaged? Starting to get into the realm of "there should be a code thrown"


Could the cam be installed out of time?




What were your compression test numbers?
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  #23  
Old 09-10-2019, 08:05 PM
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I haven’t scoped them but my scan tool shows there is a cam and crank signal both when cranking and running. I have also inspected the reluctor wheel and verified it has a 58 tooth count. I know the earlier duramax used a 57 tooth. To clear things up the block was complete to the pan including the front cover. Although I only inspected each cylinder and dropped the pan to inspect the bottom end. The heads were tested and machined. I have gotten it to throw a p0336 when I ran in it for 10 or 15 seconds with it knocking but I think it’s because the rpms were bouncing around so bad. I then proceeded to test the ckp circuits and all tested ok. Cleared the code and have not gotten it to return.
The cam for an lbz wouldn’t be timed differently than an lmm right?
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  #24  
Old 09-10-2019, 08:18 PM
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Have you bled the air out of the filter head and ensured its not sucking air through the primer? and again, what were your compression test numbers?
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  #25  
Old 09-10-2019, 08:22 PM
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Pull the fuel pressure regulator and see if it will stay running under 1200 rpm. That would eliminate fuel pressure issues or injectors returning too much fuel. It will rough kinda crappy but would know if it fuel related or not. It still sounds like it is fuel to me.
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  #26  
Old 09-10-2019, 08:48 PM
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Yes the air has been bled and I have ran it with clear lines in and out. No air. I’ve also unplugged the regulator. No difference.
As for compression my lowest cylinder was 380 and all are within 30 psi of each other.
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  #27  
Old 09-10-2019, 09:28 PM
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Quote:
Originally Posted by dmaxfireman View Post
This, and with the motor being in the bed of the truck any chance the reluctor wheel was damaged? Starting to get into the realm of "there should be a code thrown"


Could the cam be installed out of time?




What were your compression test numbers?
The cam timing issue is another one of those “should throw a code” situations. I don’t like those refurbished computer sellers. I have had too many issues from the junk they sell. I would find a known good running LBZ that you can borrow an ECM from to do a test. You will have to do a VATS relearn, but it would rule it out. It’s a very odd problem for sure.
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  #28  
Old 09-10-2019, 09:59 PM
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Quote:
Originally Posted by Unlimitedauto View Post
I havenít scoped them but my scan tool shows there is a cam and crank signal both when cranking and running. I have also inspected the reluctor wheel and verified it has a 58 tooth count. I know the earlier duramax used a 57 tooth. To clear things up the block was complete to the pan including the front cover. Although I only inspected each cylinder and dropped the pan to inspect the bottom end. The heads were tested and machined. I have gotten it to throw a p0336 when I ran in it for 10 or 15 seconds with it knocking but I think itís because the rpms were bouncing around so bad. I then proceeded to test the ckp circuits and all tested ok. Cleared the code and have not gotten it to return.
The cam for an lbz wouldnít be timed differently than an lmm right?
You may still have a loose reluctor if you didn't check it already, I'd check that and scope it. Overlay the signals on the screen if you can. If that checks out, and you're sure each injector connector terminal is tight (internally), then I would agree with Josh and say get a different ecm to test quick.
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  #29  
Old 09-11-2019, 11:00 AM
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Well I hooked up the O scope this morning and the cam and crank signals are good. I’ll try to get my hands on another ecm. I guess a fuel map or something could cause this? As for the injectors, I can cut each one out with my scan tool and I inspected each connector but I haven’t drag tested them. I would imagine if I can cut the injector out they are making good contact right?
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  #30  
Old 09-11-2019, 12:44 PM
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While you're searching for a good known ECM.... Can you get a video with clear audio of the truck trying to start / idle / run at the lowest rpm you can maintain.


Also, while you're waiting, icepick all of the injector connectors. It can't hurt.
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