CM871 poor power and fuel econ
09-17-2022, (Subject: CM871 poor power and fuel econ ) 
Post: #64
RE: CM871 poor power and fuel econ
Quickserve.cummins.com is also your friend. Take a look at sympton search/ runs rough or misfires.


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09-19-2022, (Subject: CM871 poor power and fuel econ ) 
Post: #65
RE: CM871 poor power and fuel econ
(09-17-2022 )Grounded Pilot Wrote:  ...
I re ran the overhead and everything was within tolerances. Re ran the leak test and still getting bubbles. #1 & 2 on the front bank. Haven’t switched to the rear bank again but will in a bit, had to run in town and take care of some things quick. I’m assuming I’ll get bubbles there as well. So back to square one as to why I have 3+ injectors bad in under 9 months?

There are a couple causes of premature injector leakage failures on ISX's.

The most common is air getting into the fuel, eating up injector tip.

The other is some kind of engine abuse. Things like power set to way more power than the tier injector was designed for, or excessive boost (more than about 37-38~ish psi) and pushing the engine hard a lot.

Other than that, it could be injectors that were on a recall list or something?...
ref: http://rawze.com/forums/showthread.php?t...08#pid2508


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09-19-2022, (Subject: CM871 poor power and fuel econ ) 
Post: #66
RE: CM871 poor power and fuel econ
(09-19-2022 )Rawze Wrote:  
(09-17-2022 )Grounded Pilot Wrote:  ...
I re ran the overhead and everything was within tolerances. Re ran the leak test and still getting bubbles. #1 & 2 on the front bank. Haven’t switched to the rear bank again but will in a bit, had to run in town and take care of some things quick. I’m assuming I’ll get bubbles there as well. So back to square one as to why I have 3+ injectors bad in under 9 months?

There are a couple causes of premature injector leakage failures on ISX's.

The most common is air getting into the fuel, eating up injector tip.

The other is some kind of engine abuse. Things like power set to way more power than the tier injector was designed for, or excessive boost (more than about 37-38~ish psi) and pushing the engine hard a lot.

Other than that, it could be injectors that were on a recall list or something?...
ref: http://rawze.com/forums/showthread.php?t...08#pid2508

I could not get the rear bank to bubble except for when turned over by the starter. Hand cranked that dang engine for about 20 min trying! As far as the power, it’s still set how we discussed via email and gets about 35psi boost. However, it was getting 39+psi before we reprogrammed it 6 weeks ago and timed wrong.

I will get the fittings to check the air in fuel problem. The mechanic thought that was a problem a while back and I changed all the fuel lines from the tanks to the lift aux fuel pump inlet. Also pulled the IFSM and changed it due to the mechanic thinking it was possibly cracked internally. Put all new gaskets and o-rings on it then. But didn’t seem to make any difference. Have not rebuilt either the aux or main fuel pimp as it maintains fuel pressure evenly on insight.

I haven’t checked recall status, but I’ll get the serial #’s and check.

I had to hit Kenworth to grab a exhaust stack bracket and caught a tech while I was waiting on parts. His conclusion was that I have injector cup issues due to the carbon “slime” build up around/above the first “step” closest to the tip on the injector. Does this sound like a plausible explanation? Only about 350,000 miles on the head “supposedly”.

If it’s the injector cups, is that a changeable part on an cm871?
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09-19-2022, (Subject: CM871 poor power and fuel econ ) 
Post: #67
RE: CM871 poor power and fuel econ
(09-19-2022 )Grounded Pilot Wrote:  ... His conclusion was that I have injector cup issues due to the carbon “slime” build up around/above the first “step” closest to the tip on the injector. Does this sound like a plausible explanation?
...

If there is coolant flow restriction to the injector tip then yes, it can get leaky faster then it should. It will also be a visible problem when the injector is removed, via a visibly blackened burnt-looking end on the injector.

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09-20-2022, (Subject: CM871 poor power and fuel econ ) 
Post: #68
RE: CM871 poor power and fuel econ
These are a few of the original injectors I’ve taken out recently. I wiped them clean a little bit before the pics, which I realize would have been helpful now. But they all had a black KY jelly slime up to about the top of where your pic shows the black/burnt area on the injector Rawze. And some up a little farther, closer to the o-ring on the injector. [/code]


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09-20-2022, (Subject: CM871 poor power and fuel econ ) 
Post: #69
RE: CM871 poor power and fuel econ
coolant system contaminant or additive?.

and why is the oil so black and nasty?. Looks like the whole engine is saturated with soot. - That is not normal either unless the EGR is active and no one is changing the oil often enough vs. its fuel economy.


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09-21-2022, (Subject: CM871 poor power and fuel econ ) 
Post: #70
RE: CM871 poor power and fuel econ
(09-20-2022 )Rawze Wrote:  coolant system contaminant or additive?.

and why is the oil so black and nasty?. Looks like the whole engine is saturated with soot. - That is not normal either unless the EGR is active and no one is changing the oil often enough vs. its fuel economy.

I put new trans cooler lines and heater core lines on it last winter. Blew a line so figured I’d replace them while I was greasy. But I drained the coolant and refilled it with a 50/50 mix of the red final charge OAT coolant. Water filter was replaced after these photos. No telling really what was in the coolant prior to when we purchased it. We have figured out that it was a fleet truck so I’m betting it was getting the 50k between oil changes treatment. I’ve ran it for 100k miles and we change it every 12-15k with delvac. And I’ve been replacing half a gallon with 80/90. I haven’t put any oil additives (except 1 gallon of Lucas in the first oil change) in otherwise and have not put anything but the final charge pre mix in if I needed to add coolant.

As far as neglect goes, if this thing had a voice I’m sure it’d be screaming for help. But it’s revealed enough since I’ve been working on it to know it has had a rough life. She’s in rehab though!

Is there any oil additive that actually helps clean the internals out?
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09-21-2022, (Subject: CM871 poor power and fuel econ ) 
Post: #71
RE: CM871 poor power and fuel econ
(09-21-2022 )Grounded Pilot Wrote:  
(09-20-2022 )Rawze Wrote:  coolant system contaminant or additive?.

and why is the oil so black and nasty?. Looks like the whole engine is saturated with soot. - That is not normal either unless the EGR is active and no one is changing the oil often enough vs. its fuel economy.

I put new trans cooler lines and heater core lines on it last winter. Blew a line so figured I’d replace them while I was greasy. But I drained the coolant and refilled it with a 50/50 mix of the red final charge OAT coolant. Water filter was replaced after these photos. No telling really what was in the coolant prior to when we purchased it. We have figured out that it was a fleet truck so I’m betting it was getting the 50k between oil changes treatment. I’ve ran it for 100k miles and we change it every 12-15k with delvac. And I’ve been replacing half a gallon with 80/90. I haven’t put any oil additives (except 1 gallon of Lucas in the first oil change) in otherwise and have not put anything but the final charge pre mix in if I needed to add coolant.

As far as neglect goes, if this thing had a voice I’m sure it’d be screaming for help. But it’s revealed enough since I’ve been working on it to know it has had a rough life. She’s in rehab though!

Is there any oil additive that actually helps clean the internals out?

Do your next 3 oil changes at 3-4k mile intervals. Drop a 1/2 gallon of diesel into the oil and run it around the block a mile or so just before oil change. That is the cheapest way to flush all the years of soot out of it.

After those 3 oil changes replace the oil at intervals based on fuel mileage.. and not some dumb random number mileage like you mentioned.
here is a reference:http://rawze.com/forums/showthread.php?tid=8117&pid=70681#pid70681

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As far as the coolant system goes.. nothing beat 'Cumming restore' when used exactly as directed. It will flush the coolant system out. -= follow it up with a couple water-only flushes (few miles of driving it around at a time).. and then put regular 50/50 red in it and stop putting any other additives in there.

Use the coolant filter that does NOT have the sca impregnated into it. Cummins makes both types.. make sure you have the one that is not putting additives in there.


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09-24-2022, (Subject: CM871 poor power and fuel econ ) 
Post: #72
RE: CM871 poor power and fuel econ
Thanks, I checked the list and probably need to go about 10-12k. Averaging about 5.8mpg since the retune. I checked the water filter and it is a chemical free one so that’s good! Lol!

I ran a air in fuel test when I got home today and it has a bunch of tiny bubbles in it. I’m assuming that’s a NO NO according to what I’ve read in regards to the test, but it’s the first time I’ve ever ran it. I will post a video. I had it cracked open so that the tube was full and had a good stream coming from the end. But I’m pretty much in the dark as too how fast the flow should be. I bypassed the water separator and didn’t change the test. It has new fuel lines from both tanks to the splitter and to the aux fuel pump.

Fuel filter was replaced 8k miles ago because I got some junk B20 fuel. I’m going to get a new one tomorrow and get it put in then test it again.


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