2008 Ram 3500 6.7

Dustin Owner/Technician Oklahoma Posted   Latest   Edited  
2008 Dodge Ram 3500 Laramie 6.7L (A) 6-spd (68RFE)
Pops Out Exhaust

This truck is kicking my rear. Truck has around 85k miles. Last year we replaced the fuel system due to bed removed customer driving till fuel system died do water contam. Owner has put a new bed complete with stacks. And gave truck to 16 yr old son. Called said one the injectors must be bad. When he pulled it off the trailer, it had a popping noise coming out the exhaust like an exhaust valve not closing all the way isolated to a cylinder and truck has def vibration. I did quick cylinder kill test with Witech2 and when cylinder 5 killed truck smoothed right out quit knocking. So swap cyl 4 and 5 injectors to see if knock moves. Stayed at cylinder 5. Relative comp test looked good. Compression in cyls 5 and 4 was around 420psi. What also cause me concern was the when cranking for rel compression motor shook so bad I thought crank was out of balance. Removed torque convert bolts and balancer still shook alot. 

Decided to remove the head and check valves anyways. Put head on bench filled exhaust runners with diesel all exhaust valves leaked a little. Machine shop done valve job. Checked piston height all was good nothing there, also marked the #5 intake and exhaust push rods at there highest lift and compared to cyl 4 pretty much same. We then pulled the cam and lifters for inspection didnt see anything wrong. Pulled oil pan nothing in pan rotated motor by had didnt see any visual problems. Endplay was good on crankshaft. 

Put head back on. Ran the valves. Started up motor sounded as if running on 3 cylinders now I got dtcs for open injectors cyl 4,5,6 start to ohm the harness from vc to 60pin ecm connector. I swear they were open. Then recheck and they show continuity. By now I am so frustrated I cant think straight. Start truck running on 6 shaking again and popping out exhaust. Do cylinder kill test and it moves to cyl 2. Swap 2 and 1 injectors, and rockers off cyl 2 to cyl 3 miss stays at cyl 2. Grab Pico and low amp probe clamp around inj 1 control circuit grab capture kill cylinder see capture go pretty much flat, do same on cyl 3 goes flat, clamp cyl 2 and when I kill it stays normal but popping quits, smooths up. Times out back popping and running rough. I have tried another ecm same issue. Does anyone have a good scope capture of cam and crank relationship on 07 or 08 6.7 dodge? I got some spare ecm pins from cummins and am planning on an overlay of cyl2. But the only logical conclusion is there has to be something in the harness causing issues or maybe crank cam relation ship?

Any ideas welcome. I am pretty much stuck right now. I got original ecm back in it and stock flash. Sorry for any misspellings or run on sentences.


Finally figured this truck out. Brandon Steckler helped me get thru it with some good tips etc. It ended up being an injector bad. I didnt have any balance issue with crankshaft seems all these 6.7 cummins shake alot when cranking. But with Brandons help we discovered I had an injector firing late. I suspect it was firing when exhaust valve was opening and we had an ecm reset at times the injectors would quit firing then pick up. No excessive black or white smoke.

I will recap what happened. Truck had fuel system replaced over year ago by me. My buddy calls said truck missing possible injector problem. He drops it off and one my techs uses the snapon scanner and runs through cylinder kill test. When he selects cyl 5 pop goes away. Well the next day my tech moves injector 5 to cylinder 2 hole and cyl2 injector to cyl5. Next we used the witech and perform cylinder kill test. Selected cyl 5 and miss goes away. So that makes me think injector is not issue cause miss didnt move. And when doing cyl kill with witech on a cummins When you command a cylinder to die. It kills them in the firing order. 1-5-3-6-2-4

So when selecting cyl2 it kills inj5 and selecting cyl5 it kills inj2. That really led me down wrong path early on.

Thats when we pulled head, camshaft, lifters, oil pan to inspect things. And when we put it back together with injectors back in original holes. And use witech again to do cylinder kill test. And command cylinder 2 kill the pop out exhaust quits. Now I am thinking how that is possible. I put low amp clamp on cyl 1 grab capture then cyl2 grab capture dont see any difference. So I then grab inj 1 trace command cyl1 shut off it does, 3 will shut off, cyl2 wont kill injector when commanded by witech. I thought must be ecm issue. Check wires for shorts no issue. Put a ecm in it and still had same problem. I am really mad now running out ideas. Grabbed a snap on scanner sometime and went over the inj kill testing with amp clamp on each injector to verify injector shuts off. When I command inj2 it shuts off? Weird. I then tried witech and cyl2 wont shut off. I figured out the witech when commanding cyl2 injector off turns off inj5 and when selecting inj5 it shuts off inj2. That really messed me up.

So I messaged a guy for a waveform and he said to try first look in exhaust and trigger off cyl 1 grab cam and crank signals. I had sent same capture to Brandon and I asked him confirm it was cyl5 exhaust pulse that was diff then rest which he agreed. I guess I also forgot to mention to Brandon that the factory scan tool messed me up also. But he also noticed that the ecm would reset or drop all injectors at times. He also had me use low amp clamp around all 6 low side wires of each injector which was awesome tip just took some work to get access to do it. And suggested I pin drag some connectors which I did and they seemed tight to me. I cant thank Brandon enough for his help. He just got me thinking straight. Any ways I sent him diff pico captures. And sunday I went back to the shop. Grabbed captures of injectors again. But this time I decided to disconnect 1 injector at a time. 1-6 When I unplugged inj1 truck popped out exhaust and would reset ecm. Same for inj 2, 3, 4,6 but when I disconnected inj5 the popping out the exhaust quit, and the ecm quit reseting no injectors would drop out. That was a big clue to me. So then I decided to move inj 5 to cyl1 and inj1 to cyl5 see if things changed. I was hoping they would. I dropped the first look back in the stack and triggered off cyl1 and watched the misfire pop out exhaust move to cyl1 best feeling ever there. Has be injector issue. Sent Brandon another capture to verify. Brandon then said we know whats wrong but whats causing the reset of ecm? I grabbed attenuators and backprobed inj1 got capture and got capture of inj2 with inj 1 discconected. Brandon will have to look at those files I didnt see anything. And I ran the suspect injector back to my supplier and had it warrantied. They are gone put it on bosch stand send me there results. New inj installed and it runs like a top. Reprog inj iqa numbers. Put tune back on. Got test drive it tues.

Pump shop called said injector passed all the bosch bench tests. I asked how they checked the solenoid. They said bosch makes handheld device that measures ohms, tests the stator. But I told them truck runs like champ. And pump shop said they seen this one other time with 5.9 injector.

I guess it was a good learning experience for me. Never thought SnapOn would be correct. And witech kills cylinders from firing order. Plus I learned some about the first look in the exhaust and can apply all this to most common rails. Even had a 7.3 in no start used some amp clamps to verify injector operation. I try get some captures or screen shots up later. 

Albin Diagnostician
Albin Default

Dustin, I feel your pain. The first thing that caught my eye was the 16YO driving this rig :) I can't help you with the scope capture, although, it has been my experience that a popping noise like you have described can be caused by only two things; One is a mechanical problem with the engine, the other is n injector that is being commanded on at the wrong time. Over the years, I have used my…

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Dustin Owner/Technician
Dustin Default

Albin I agree with you my first thought was mechanical issue with motor possibly exhaust valve related. I would bet $100 on that. However the slight leakage of the valves got me think that was not the problem. And now I am kind of convinced that the injector on cyl2 is adding fuel at wrong time. And when I use witech to turn off that injector motor smooths up quits popping. I have triple checked…

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