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

Alright Mr. Cummins your move: 6 new crossover tubes from cummins, 6 new Orings, and 2 grid heater gaskets

 

My cross over tubes so far have made a good change to my truck and how it runs. As for misfire I'm not going to call it cured yet till I do some long hauls and see.

 

Now as for my grid heater gasket I love to steal yours. But mine are on there way and be at work by Monday.

Cummins dealer was the cheapest place I could find the grid gaskets! 5.28 each

Tubes were 25.67 each with O rings. O rings separate were 18.95 smh! Came out to be a few bucks more expensive than ordering, but no shipping and I got them tonight

That's better that what Rocky Mountain Cummins (of Boise, ID) quoted me for one cross over tube at $166.40 a piece (or $998.40 for six).

RAPE !!!!!!!

 

Ed

Well I have everything in and...... No luck. It doesn't sound like the miss has changed at all. Sounds internal to me. The whole fuel system has been gone through

interesting...

Edited March 7, 201510 yr by CUMMINSDIESELPWR

Ok. Question do you do the compression test on a cold engine? You might do a blow by test on cold and hot and see if there is a measurable difference. Then if you can quick enough pull the injectors and re-do your compression test hot. I'm wondering if it like JL Welding where he had a cracked piston that would only open up after fully heated.

 

Plain weird... Diesels are such simple engine only requiring compression and fuel. To have a misfire means either one or the other is missing.

 

The only thing that crosses my mind as a odd factor is possibly timing? I know the lines if removed in a group you can't mess up. front group is 1,2,4 the rear group is 3,5,6. Firing order is 1,5,3,6,2,4. The only reason I'm thinking this is common for people with gassers to cross plug wires and get a odd miss that never goes away.

 

So did your fuel leak stop too on the manifold?

Honestly I'm tired of trying to find this miss. I'm not going to do anything else until I pull the motor out. If there is something wrong down inside, I'll see it when the head is off. I will also see if the timing gears are all lined up at the same time. injection lines are in the correct order. I took them all off and cleaned them with a green scotch brite pad.

 

It appears like the leaks have all stopped but I need to go wash the motor to be certain

How about a valve hanging open for a split second? Maybe pull the valve cover and watch while cranking?

I was told long time ago " The longer you wait to fix something, the easier it will be to diagnose the problem".

pull the head already, have the head pressure tested and inspect the pistons. dont throw anymore money at.

Edited March 9, 201510 yr by CUMMINSDIESELPWR

pull the head already, have the head pressure tested and inspect the pistons. dont throw anymore money at.

 

 

 

Agree^^^^

 

This is sounding more like a piston or head gasket thing!!

Man TFaoro, I wish your problem was as easy as mine. After changing the cross over tubes and this this weekend hitched up and went to Huntington, Oregon to go out for the first RV trip of the year. Absolutely no more miss and the truck ran strong.

 

I hate to say it but I guess you going down that road of full pull down to see what's going on. Something isn't right cylinder wise.

Little update here. Thanks for the thoughts guys. The miss doesn't seem to have gone away but I don't think the old tubes were completely seating against the injectors. I can now pull more boost, spool the turbo quicker, and have lower EGTs. That dang miss is still there though. Weird thing is when it has a significant load on it you can't tell it's there.It still makes Tons of power, spools really fast, and has zero blowby.

 

To the head coming off... That will happen in time. Right around the middle of may the motor will be on the garage floor, so I'll do it then. Thanks again everyone for the help!

Little update here: I'm starting to get a bit of blue smoke when idling and high idling. Even when the engine was up to 145deg it still had a decent haze coming out of the tail pipe. I haven't noticed any consumption on the dipstick though. Maybe this is related, maybe it's not. I'm also noticing that warmer ambient temps seem to make it worse, along with switching to 6cyl mode when idling. I'm not sure if that's related to timing or??

I'm getting pretty ancy wanting to pull the motor! 4 weeks and it should be coming out.