Alright guys I am experiencing a miss at all RPMs. It is pretty noticeable near the engine with a knock, but is extremely noticeable at the exhaust. It is easy to feel that the exhaust is "puffing" per say. Now I just replaced the injectors with a new set of 125hp sacs, but the miss was prevalent before the injector swap. The swap did not make a difference. Everything sounds the exact same as before the swap. I have fuel squirting out of each connection at the cross over tubes while running.

MoparMan and I spoke on the phone earlier and have decided to take a systematic approach to resolving this issue.

Ruled out: 1. Injection pump: Always supplied good pressure, less that 10K miles and miss seems to only be in one cylinder. 2. Injectors: Swap made no difference.

Possibilities (Almost endless): Burnt/ broken valve, broken piston or piston rings, clogged cross over tube, valves way out of adjustment

 

I should receive the truck Friday from being painted and I can start diagnostics. 

The plan: 1: Pull valve cover and quickly check valve lash - just make sure somewhat close to spec. 2. Use an infrared heat gun on the exhaust manifold right were it come out of the head to try and narrow down which cylinder is missing. If that does work I will pull the cross over tube and replace it (I already have 1 new one that will ship out Monday). If that does not fix the issue I will do a compression test on that cylinder to determine if it is the bottom end or the head.

If the heat gun does not find a "cold" cylinder I will pull all injection lines and cross over tubes, then clean each tube and try to determine if there is debris in one of them. If I can not find debris in any of them I will replace them with the new one, one at a time. If that proves inconclusive I will perform a compression test on all 6 cylinders. 

If any of the cylinders are low on compression I will pull the head and determine what is wrong internally.

 

Any suggestions on the procedure or something else I can do to diagnose what is wrong with this thing??

Edited October 26, 201410 yr by TFaoro

both ends will be cooler. they are not 'sharing' heat from another cylinder.

Every 6 cylinder I've ever tested does this... running good or not.

* this is really evident for initial warm up* They (ends) take longer to build heat. Even after fully heated, they like to be somewhat cooler.

Most 'dead' cylinders I've gunned, were usually 100 degrees or more cooler than 'good' cylinders.

Edited November 9, 201410 yr by rancherman

None of the cylinders are completely dead, which is making this harder to diagnose. The new tube definitely helped, so I believe it is still fuel supply related

I meant to say, 10-50 degrees isn't really that far out of the 'normal', even in a perfect engine..

A completely dead cylinder will make hot air just from the compression, (as long as you don't have a valve issue) and will be around 100 degrees cooler than a live firing one. (at idle)

I think you're on the right track.. fuel delivery.

I did a little driving this morning. It seems like the miss gets somewhat worse as temperature increases. I also have fuel coming out of #3 and #4 next to the head. I will have to check and see if that is the O ring leaking or the injector line not seating against the crossover tube. 

how tight are the injector hold down plates?

I torqued each one to 89 in-pounds per cummins specs. I'm thinking loosen the injector lines, loosen the injector hold downs, snug the injector line, and re-torque the injector hold downs. That should make sure the crossover tube is properly seated into the injector. 

I have narrowed it down to one of the three rear cylinders. This morning it was 12deg F! Flipped to 3 cyl high idle and it was obvious that the miss was still there. What is the best way to check those cylinder temps? With the engine warm or the engine cold? Thanks guys

Let it warm up, but not to much. You don't want to heat soak the engine or manifold before temps are taken. I would let the temp gauge just come off the bottom then check each runner. Also check all six and write the numbers down. I would also check them more than one time so you can see a pattern to the temps.

Should I do this on the 3cyl high idle? I think it would be more noticeable then

before I bought my IR temp gun, I'd just wet a finger, and go right down each cylinder immediately after a cold start. It only worked for a couple minutes, cause even a dead cylinder will get the manifold hotter than 212.

I'd usually find 5 cylinders that would "psssst' under my finger, and the 1 dead one would only leave a wet fingerprint. About half my engines use a manifold that shares pairs of cylinders for the exhaust, which makes it even tougher to isolate

Highly unscientific, but it gave me a clue on where to start!

before I bought my IR temp gun, I'd just wet a finger, and go right down each cylinder immediately after a cold start. It only worked for a couple minutes, cause even a dead cylinder will get the manifold hotter than 212.

I'd usually find 5 cylinders that would "psssst' under my finger, and the 1 dead one would only leave a wet fingerprint. About half my engines use a manifold that shares pairs of cylinders for the exhaust, which makes it even tougher to isolate

Highly unscientific, but it gave me a clue on where to start!

Thanks for the tips! It is supposed to be down to 0deg F tonight... I don't thing I will be working on it till the weekend! On a positive note at 12deg F this morning it fired just as fast as it does when it's 100 out

before I bought my IR temp gun, I'd just wet a finger, and go right down each cylinder immediately after a cold start. It only worked for a couple minutes, cause even a dead cylinder will get the manifold hotter than 212.

I'd usually find 5 cylinders that would "psssst' under my finger, and the 1 dead one would only leave a wet fingerprint. About half my engines use a manifold that shares pairs of cylinders for the exhaust, which makes it even tougher to isolate

Highly unscientific, but it gave me a clue on where to start!

Just used this this morning! Engine temp was 15deg F and I started it popped the hood and felt each runner individually. I figured One and 6 would be the coolest, which they were but 6 did NOT warm up much (I could hear it missing). The other 5 got hot enough I couldn't keep my fingers on them but 6 stayed relatively cool. I believe it is just the tube not seating into the injector properly.

Sounds like your making head way.

My strategic approach got kicked in the face from having no time and this wave of storms. I will keep this thread updated whenever I manage to tear things apart. I plan to pull valve cover, loosen all injectors, pull all of the fuel lines and clean up the mating surface, pull crossover tubes  and clean mating surfaces, then re-install everything in the proper order. If that doesn't work I guess it's compression testing time

Alright update here I want to know your thoughts. I picked up a set of crossover tubes from a guy for 50 bucks. They had been drilled to .093 and he said they worked great on his truck but he sold the truck and pulled the aftermarkets. I figured for 50 bucks I'm not losing much and at least I know none of the tubes are plugged. I pulled all of the injection lines, cleaned the ends with a scotchbrite pad and blew them out really well. I then  pulled all 6 exhaust rockers and loosened up the injector hold downs. (Yes I kept the rockers in order 1-6) I then installed the crossover tubes and injection lines. I snugged each line then tightened the injector hold down for all 6. I then threw everything back together and got it running. I was out in 22 degree weather standing in the snow so it was pretty miserable. Well my miss is not gone.... I tried loosening each injector line and re tightening with no luck.

 

Ok here's the twist to all of this! As I was driving home from my sisters birthday party tonight (Before installing the new tubes) it started to run smooth... but only for 4 or 5 seconds at a time then went back to missing. Now with the new tubes it was doing this on the high idle. It would miss for anywhere from 10 seconds to a minute then run smooth for 4 or 5 seconds. I finally got pissed enough and called it a night at midnight. What do you guys think it could be given these new symptoms? I still have the smarty on level 1 so I guess I can return everything to stock and see what it does. Oh and no codes and 20psi fuel pressure. Sorry about the ramble! Looking forward to hearing from everyone

Time for pop testing. Number and label thee injectors. Find out what going on injector wise.

You think it could be injector related?? These things have maybe 500 miles on them and when I changed from the 90's to the 125 SAC's there wasn't any change at all with the miss.

I just got a video I think you can hear pretty well. Make sure your sound is all the way up!

 

As you can tell it is NOT a completely dead cylinder but you can hear the "knock" I guess of it missing a bit

Edited November 15, 201410 yr by TFaoro

Alright I just went out and tested all cylinder temps when the engine was 85 deg. After about 1-1.5 minutes running, #1 was 135-140F I measured it all around the manifold right next to the head. I could keep my hand on it for quite a while without burning it. All other cylinders were 165-170 F. I Do you guys think that is conclusive enough to say #1 is my problem? Where do I go next? Swap injectors with #3?? I'm kinda lost at this point

Like Mike said, I would probably be having them injectors pop and flow tested if possible. At the very least its pretty cheap and it will rule out the injectors for sure.