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

Just trying to come up with an answer for something that I cannot answer....

 

Ed

Could it be bad fuel

  On 1/1/2015 at 4:21 PM, Dieselfuture said:

Could it be bad fuel

Nope... I've been through many full tanks of fuel and at least 2 or 3 filters. Everything has been spotless. Thank you for the suggestion though

No problem just thinking out loud, sometimes we overlook the simplest things.

i dont remember seeing if a borescope has been used to inspect the cylinder and piston crown for cracks or holes burnt through.  it would make sense if there is a miss or dead cylinder/partially dead cylinder.

He has done compression & leakdown tests, 3 sets of injectors, crossover tube O rings, now had the pump inspected by Industrial Injection.

Ed

Edited January 3, 201510 yr by Mopar1973Man
Expanding the acronyms

  On 1/1/2015 at 9:22 PM, Yankneck696 said:

He has done compression & leakdown tests, 3 sets of injectors, CO tube O rings, now had the pump inspected by II.

Ed

Then like I said, check the valve train.......... A worn cam, bent pushrod, rocker arm issue, etc.

i might be way off here, and may have missed it. but don't the cross over tubes have some sort of screen in them? maybe one plugged? won't a cracked ring do this as well?

He also swapped out drilled crossovers, too.

 

Ed

Ok so how about cam or crank sensor? They may not be faulty all the time but random faults from engine vibration could cause the same kind of issue.

  On 1/1/2015 at 11:10 PM, mulcher812 said:

Ok so how about cam or crank sensor? They may not be faulty all the time but random faults from engine vibration could cause the same kind of issue.

Good thought, but I have a scangauge and the rpm meter on it does not bounce around or drop to zero. 

 

I will go through pushrods and rockers tomorrow. 

Is there a way to crank engine over without starting, if so maybe try cranking it over and listen for any odd miss. From what I heard all cylinders should sound same and if there is an odd one then you know it might be something internal.

  On 1/2/2015 at 1:49 AM, Dieselfuture said:

Is there a way to crank engine over without starting, if so maybe try cranking it over and listen for any odd miss. From what I heard all cylinders should sound same and if there is an odd one then you know it might be something internal.

I don't know if that would do much. Since there was a compression test done and everything so far checks out good, there isn't much left to check.

just a wild thought...  is there an extra copper washer in #6 by chance?  just throwing darts now...

The scan gauge is seeing everything that the ecm is seeing. I think the crank sensor goes straight to the vp. So try wiggling the wires when its running and see if it stops.

Crank/cam sensors go to the ECU. The VP44 has it's own tone wheel & hall effect sensor.

 

 

Ed

Edited January 2, 201510 yr by Yankneck696

After reading all that you have gone round with it is difficult to find any new suggestions.

However, I will ask if you have biodiesel available in your area and if you ever use it.

It is an excellent cleaner and has great lubrication properties. 1% bio increases the lubricity of your fuel by 1000 from what I understand.

Just make sure you get it from a good supplier so there is no water in it.

 

I assume when you say crossover tubes you are talking about the fuel lines between the engine and the injectors.

If not then I would ask what the condition of your fuel lines is.

 

Biodiesel should help either way, use a couple gallons per fillup to improve lubricity and clean the system.

Crossover tubes are the part between the injector lines & the injector, going through the side of the cylinder head.

 

Ed

Wild shot in the dark. How about the wrong thickness copper shims being used on one the injectors?

Adjust your valves. That will tell you IF you are having a valve train issue.