Cummins ISX CM871 Technical discussion

Duramaxxed and kwcam...thanks for that too. I'm 100% with you on it. I see how the system is designed, with the rocker shafts doubling as the supply for the oil, and how important the other components are along with the rockers and shaft assemblies. It's also very evident after seeing things first-handedly that clean oil is critical in the smooth operation of these integrated braking systems. It doesn't take much to contaminate just one small orafice that supplies oil pressure to this component and make it malfunction. Luckily mine is functioning like a new one at the moment...

While I have the attention of both of you competent men here, I am struggling now with the grim reality that I may have some worn or broken ring issues going on. This engine supposedly only has 350K since a major out-of-chassis overhaul, and I verified that with the rebuilder before I bought it. But, that doesn't guarantee that the previous owner/seller took care of it very well either. I found that out with the oil change interval being 40K miles overdue according to the notebook he gave me with the truck.

Before and after me servicing this engine since Friday and today, I have been watching the exhaust ports weeping motor oil when I am running my product pump transferring product from my tanker to a storage tank. Twice now, I have been watching the oil coming from in between the turbo/manifold mounting flange AND primarily from #3 & #4 exhaust ports themselves. It's evident that there's oil getting by the rings especially from #3 and 4... Only seems to do it at high idle (about 850 rpm) while pumping for 45-50 minutes. Then when I take off, I fog the entire place up until it clears out. Looks like the manifold loads up and when I get into the throttle it blows the oil out for a minute until clear again.

Doesn't do it at all during normal run time, probably because it's being burnt more than passing by rings under a no-load...? It tends to smoke every gear you grab, and it does trail a slight fog all the time under power especially. I'm expecting it to consume a gallon of oil per week at least, this week will be the first test since the new oil, injectors, and engine brake problems were addressed this weekend.

What's your opinion? You thinking the same thing as I am...she's got some excessive wear or possible ring issues that I'll be addressing some time in the near future? I would LOVE to get through the season and into the spring before I tear into this engine again...if nothing else, just to say I actualy made .12 cents with it before I spend another few thousand, lol. I dread one of those $25,000.00 overhaul deals. That's unethical, un-natural, and unhealthy.

 

Are you sure that its oil? Fuel can do the same thing that you are describing.

 

I'm not 100% sure it's oil, no...I'll analyze it closer the next time I run the product pump. I'll be taking another oil sample shortly too, to determine more.

Could be right on that. Bad injector seat, etc...As I watched it sort of "bubble" out between the flange of the turbo/manifold, that thought crossed my mind that it could be fuel, as it appears to be thinner than oil to act like this. I'll watch oil consumption closely as well, to try and figure out where it is going.

Thanks!

 

How old is the turbo?

 

I've had bad valve stem seals on the 871 before. The 2250 has bad valve stem seals all the time lol.

 

If concerned of a broken piston ring issue, there would most likely be high blow by with it. A simple blow by test will show the "health" of the engine. (you don't want to see numbers of 18" h2o as this is Cummins max limit)

The slobber from the manifold sound more of a fuel issue, possibly from bad injector or low compression where it is not able to burn completely. If you chose to remove the injector(s) what I like to do is with my rubber tip blow gun will pressure up the cylinder, with valves closed, this way you can hear and see if it leaks past rings, exhaust or intake valves. a mist coming up through the head oil drain holes is bad rings/liner scuff issue. even found some bad head gaskets this way. hope this helps.

 

Good question. I was leaning towards a seal going bad in the turbo myself as another theory, because the bubbling of oil (or fuel maybe,) is coming right directly from behind the turbo mounting flange at ports 3 & 4.

It seems to be getting worse the past week, unless I'm just more aware of it than I was previously and I'm paranoid now.

 

Yeah, there's really not an excessive amount of blowby either, I've been aware of that constantly. Another injector being faulty...could be. We did that cutout test last Thursday with the laptop, but that still doesn't rule out a leaker I guess.

This thing consumes oil more than it should, the reason why I am leaning towards oil rather than fuel but it could be a mixture. Thinking about turbo oil seal now, as it's right in line with #3 & #4 exhaust ports where I see this weepage/bubbling where the turbo mounts to manifold flange. That would be a beautiful find if that's all it was.


Not much I can do right now...gotta watch it closely and maintain things until I actually make a dollar without dumping it back into this thing like has been the case the past month.

I am going to monitor things very close with continous oil samples for a while to determine if I'm diluting oil with fuel or not for now. If that's the case...it's gotta come apart then.

Thanks for all the input guys.

 

Hi guys.
Need help with CM 871 ECU electrical harness plug pin-out. Have cyl. #4 weak, the engine is shaking. One shop replaced the turbo ripoff my 5200, today have replaced the injector, another 1250. The problem still here. Removed the left harness plug and one pin is jammed and probably touching to another pin. Jammed pin is in 3 row from the top, second from the left was touching to the 3 from the left. If I'm right it's 22 and 23. Could it cause the problem?
Truck was running good then in rainy weather stars shaking badly. After engine was off - on she starts shaking much less and DPF regeneration requires every 100 miles, fuel mileage drops to 5.0.

 

We have replaced both timing actuators and it still lopes it ran good for a day and then started to lope again any ideas