Need Duramax LML cam/ crank correlation waveform

Keith Owner Arkansas Posted   Latest   Edited  
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Driveability
2012 GMC Sierra 2500 HD Denali 6.6L (8 LML) 6-spd (6L90)

I need a known good cam/ crank waveform. 

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Marvin Mechanic
Mississippi
Marvin
 

Can’t help with wave form but what the issue

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Keith Owner
Arkansas
Keith
   

I found a waveform, and the correlation appears ok….However I triggered off of the #1 injector, and it appears the injector is firing way late. Here is a pic diag​.​net/file/f6telziew… . Trace 1 is the ckp, 2 is the cmp, and 3 is the #1 injector. So my question now is why is it firing late . Also I am assuming that the ckp notch is #1 tdc..

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Marvin Mechanic
Mississippi
Marvin
 

What is problem with engine .i know if only one time wave form would have helped diagnose a problem with one and then tech bent tone wheel

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Keith Owner
Arkansas
Keith
 

Well, it won’t run. Looking at the waveform it appears that the .#1 injector is firing abou 90 degrees after tdc. Not sure what to check next…. I’ve pretty much covered all the basics. Fuel pressure and quality, compression, injector return pressure, etc …. I’m pretty sure I’ve found the problem, just don’t know what’s causing it. I'm hoping another truck with the same powertrain might come in…

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Marvin Mechanic
Mississippi
Marvin
 

So you have over 5000 psi at cranking speed…..says cam and crank signals rec…

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Keith Owner
Arkansas
Keith
   

Yes, I have about 6500 (matches desired). cam and crank both count up, cranking speed is good. Checked return pressure. Put in clear hose between filter and pump to make sure there is no air. I've used an alternate fuel source. Update. I did notice a slight variance in the cadence when cranking, so I did a relative compression test (I wish I had done this earlier) and verified that the injector…

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Marvin Mechanic
Mississippi
Marvin
 

We recently had a customer with a duramax that would not start,,,a customer we sell injectors too,,,,injectors had been in truck bosch remans less than 5 months,,,he pulled and had us test them on our bosch test stand…they would leak at tip some when first pressured up then quit when it got to 15000 or so…we went on to test injectors….we skipped a test and went on to a step that ran a pressure…

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