3.0 Duramax cranks but won’t start

[youcantkeepup!]

Its not trolling "wontstart", its legit a stupid question. If the average crank time pre update was lets say 3.5 seconds and post update is 4.25 that gives us a change on .75 seconds. Mind you these are rough numbers. The Bendix engagement into the ring gear and the bendix itself once turning, that is negligible because once turning there is essentially no wear at all. Its the initial engagement that is the peak stressors. This will be the same if it cranks for 1 second or 15 seconds. So that brings us to what will be the weak link with the additional .75 seconds of cranking. The heat generated in the starter. So now lets figure out approx how much of a delta T we see on a 60 deg day on a 3.5 s crank and how much additional heat is caused by the 3/4 of a second of continued cranking.......

 

On a quick calculation using some estimates im seeing a change of less then 0.5 deg F

[WontStart]

4 hours ago, diyer2 said:

17 minutes ago, youcantkeepup! said:

Its not trolling "wontstart", its legit a stupid question. If the average crank time pre update was lets say 3.5 seconds and post update is 4.25 that gives us a change on .75 seconds. Mind you these are rough numbers. The Bendix engagement into the ring gear and the bendix itself once turning, that is negligible because once turning there is essentially no wear at all. Its the initial engagement that is the peak stressors. This will be the same if it cranks for 1 second or 15 seconds. So that brings us to what will be the weak link with the additional .75 seconds of cranking. The heat generated in the starter. So now lets figure out approx how much of a delta T we see on a 60 deg day on a 3.5 s crank and how much additional heat is caused by the 3/4 of a second of continued cranking.......

 

On a quick calculation using some estimates im seeing a change of less then 0.5 deg F

Thanks. Could have just led with this. 

[Claxy515]

I had mine updated today. Will report back if I have any issues. The longer start is definitely not an issue, because it's such little time. I also have one of those inline autostart/stop devices in mine so that it doesn't shut off at every stop sign. Dealer didn't care/notice.

[mjm5247]

Getting reprogrammed today.  I'll report back with issues. 

[Fr3nzy]

Received my ECM flash today. One thing that stood out to me is that the crank didn’t necessarily seem “longer” as it did faster if that makes sense. Either way, so far so good. Hopefully this is the permanent fix. 

[black00ta]

I experienced the crank no start 2 weeks ago, took to dealer and dropped off same day. Got a call the next day for ECM update. Have not experienced it since. Crank time is definitely longer than before, but I thought these things always started up super quick anyway. If this is the resolution then I am happy. I cannot stand the idea of a cab-off surgery for the crank wheel issue on such a new truck.

[6sigma]

On 10/11/2021 at 9:57 AM, GJR1212 said:

I wish GM would explain what they changed in the ECU program.  My guess is they are adding some time delays to give the ECU time to see all the inputs in what is likely a long list of parameters.   Or, perhaps they are just giving the fuel pump and little extra time to spool up.

 

I'd like to know also, and I bet you are right. Given that the fix applies to 2020 and 2021 models, even though not many 2020s have the problem makes me think that it may just be a little delay to allow some sensor time to provide input. That would also make sense that a second crank starts just fine, as by then the inputs are all online. I'm just glad there is a fix. 

[macodi]

I've been pressing the start button without foot on the brake and waiting 5 secs and then starting the truck. I haven't had a long crank no start since Aug. I'll try to get the ECM flash, but I could live with this method.

[mjm5247]

On 10/21/2021 at 4:16 PM, mjm5247 said:

Getting reprogrammed today.  I'll report back with issues. 

No issues since getting the truck back from the dealer. 

 

Not seeing any negative feedback here, so it looks like we have a fix.  

[waterndirt]

 I've had mine in now 3 times, reprogrammed ECM and even had to have the dealer installed theft deterrent system removed on recommendation from GM engineers which cost me $185 out of pocket in labor expense.  

 

Ironically I was at the dealership yesterday picking up some fender flares and the crank / no start happened right in their parking lot.  One of the car porters saw it happen.  I notified my service tech and told him I'll be in touch to set up yet another visit.  The writing is on the wall for me... 

[redwngr]

5 hours ago, waterndirt said:

 I've had mine in now 3 times, reprogrammed ECM and even had to have the dealer installed theft deterrent system removed on recommendation from GM engineers which cost me $185 out of pocket in labor expense.  

 

Ironically I was at the dealership yesterday picking up some fender flares and the crank / no start happened right in their parking lot.  One of the car porters saw it happen.  I notified my service tech and told him I'll be in touch to set up yet another visit.  The writing is on the wall for me... 

What date was it in when that happened?

[waterndirt]

9 hours ago, redwngr said:

What date was it in when that happened?

Reprogram was on 9/28/21

Crank/ No Start at dealership was on 11/8/21

 

[GJR1212]

5 hours ago, waterndirt said:

Reprogram was on 9/28/21

Crank/ No Start at dealership was on 11/8/21

 

What I read says that GM released the version to correct long crank/no starts 10/1/21 and then revised it again 10/4/21.   Sounds like you still have the not had the ECU program update that addresses this problem.   

[rbdjr]

Had mine reflashed earlier this month for Crank No Start issue, 9000 miles, had happened 9 times to date. Reflashed on 11/5/21, all good so far fingers crossed. Have noticed that my engine cranks a half second longer on all start ups now, no biggie, sounds normal, just not that instant startup as before re-flash, Would like to know what the reflash has changed? 

But all good now. 

[bdallas]

I've noticed that my truck now has a slight delay on start-up from when I push the button and I have not taken my truck in for the ECM update. 

 

I have had the no start issue three or four times and about three weeks ago, when this new update came out, I noticed my truck now has a slight, but noticeable, delay on start up.

Could they be pushing this update over-the-air?