hard start, erratic tach, hard shifts [Archive] - Duramax Diesels Forum


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06-18-2014, 03:01 PM
Let me first apologize if this is the wrong forum, this is my first post.
I have a 2011 GMC 2500HD ext cab. All of the sudden the truck became very hard to start. Would crank and fire up and then shut down. At first it would take 3 to 4 times to start, today it was over an hour. Engine light is on, and tach needle is very erratic, sits at zero or bounces all over the place, and today the shifting got rough as well. installed a new cam sensor today and it fired right up as it should, tach was fine, all seemed fixed. Then i shut it off and tried again and I'm right back where i started. I thought for sure it was the cam sensor since its on national backorder via GM, I bought an aftermarket one. Any thoughts on this? Again if this is the wrong place please feel free to direct me to the right area. Thanks in advance
2011 GMC 2500HD LML
88,000 miles
All stock

06-18-2014, 03:18 PM
You mentioned the shifting was poor, this can be a result of a fuel issue. I've personally seen injection pump issues with the LML's. The only thing has me stumped is the fact your tack is erratic.

06-18-2014, 03:35 PM

06-19-2014, 11:18 AM
update: after several hard starts this morning, she finally refused to turn over. off to dealer on a flatbed.

06-24-2014, 06:45 PM
Been at dealer since 6/18 and they have no clue because they cannot get a OEM camshaft sensor. Gave me some BS about sending out a stat request. I've called every dealer in a 100 mile radius and no one has the part. i just bought another from NAPA and plan to take it to them tomorrow. I've been reading other posts about this same thing happening because of wires being rubbed thru. Anyone out there have any suggestions. I'm really stuck here. Just so you all know I'm not a newbie to these trucks, I have an 02(300k miles), 03(250k miles), 07(150k miles), and my 11(88k miles) in my fleet, 2 are gmc and 2 are chevy. Love the truck and the tranny, gone thru the normal BS with injectors and the horrible DEF system. This problem I cannot fix myself its in the electronics and that is beyond my scope.

06-24-2014, 07:14 PM
Had a similar problem with my lly. Ended up being the crank sensor.

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06-24-2014, 07:26 PM
Is the crank sensor the same as the camshaft sensor? It seems like there may be two different parts that I should be checking out.

06-24-2014, 07:34 PM
Looks the same but different part numbers. Crank sensor is just below cam sensor.

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mike diesel
06-24-2014, 07:36 PM
Check engine light is on...what codes is it throwing?

06-24-2014, 07:39 PM
thank you! i will try and get to dealer tomorrow. they will not purchase a non oem part, and the parts i need are on national backorder, therefore i'm stuck supplying aftermarket parts for them to try. i'm a contractor and losing my truck is like losing my arm.

06-24-2014, 08:33 PM
i will post codes tomorrow. Headed to dealer first thing in morning. when i scanned it it threw cam sensor code. cant remember code.

06-24-2014, 08:38 PM
So far I have these parts from NAPA:
Camshaft Sensor- OEM#97365035
Crankshaft Sensor - OEM#9736507
Only difference is , second one had a 90 degree bend compared to the Camshaft sensor

10-01-2014, 05:20 AM
Hello All
Just wanted to give some info about hard starting on a 2007 LBZ. I was having hard start problems recently, not due to cold weather, I'm in Florida. I had to prime the filter almost every morning. Finally found a filter housing O ring replacement set and installed it. No more problems!!!
Popped for the brass bleeder screw, its always better than plastic. Total cost about $14.00. Hope this helps, I know I was frustrated till I found this easy fix.