05 Monaco w/ 400 Cummins ISL low power /smoke.

[Doug_E_]

Have been trying to find out what our engine problem is for awhile now. Cummins national and Cummins West in Fresno does not know what is causing the engine to have low boost and black smoke out the tail pipe.
When we start out after a short warm-up the problem is there, drive a few minutes and pull over, shut the engine down and restart after 20 seconds. 7 out of 10 times the problem will be gone.
I asked Cummins national and after the 3rd different techs. I was told they are 2 separate issues. When I asked why both issues are gone at the same time, after the shut down, no one knew.

I've been told that a data logger might be able to detect the problem, but when I told them that there are no codes in the computer then they were unsure that this device would work.

By the way I spent $518.00 the last time at Cummins West for them to tell me the pacbrake is not the problem as well as the inter cooler is working properly and all fittings are tight.
I asked about an ECM reflash and was told this would not solve my problem.
If anyone has an idea I'm willing to try just about anything right now.

[Donna_and_Rob]

Just my 2 cents. Our Cummins Isc does some weird stuff like throwing ABS warnings, alarms going off, red lights flashing, bucking engine and transmission changing gears by itself when all she wanted was a new fuel water separator. Rob:)

[Doug_E_]

Just a quick up date on the low power and black smoke.
Cummins Pacific put my motorhome on their dyno this week.
The tech said the rig was blowing black smoke and he felt like it was down on power when he was pulling the RV into the bay.
Shut it off while he was hooking everything up including a date logger so he could document the dyno run.

Started the run on the dyno and took it up to 90% load. The data logger showed the turbo was putting out 42 lbs. of boost, and there was now no black smoke. Everything was performing just as it should.

I went to pickup our RV and asked if I could take it for a ride before we settled the bill. On this drive the RV was down on power and was blowing black smoke again. Took it back to Cummins Pacific and settled up on the bill.

Left there and now no black smoke and she is running as she should.
No one seems to be able to pin point what the problem is, I've asked if it could be an o2 sensor or a map sensor but was told no, that it would throw a code and the check engine light would light up.

Sorry to be so long winded, just very frustrated no one can fix our problem.

[wolfe10]

Don,

He may or may not have an exhaust brake. The Cummins ISL could be ordered with EITHER an exhaust brake or (more expensive) compression brake (aka Jake brake).

And, if they suspect an electrical issue, first thing is to wire a voltmeter to the 12 VDC positive wire going to the engine ECM and see if voltage drops out when the problem occurs.

Also, be sure to have engine and computer ground(s) clean and tight.

[DSDP_Don]

I would guess that your exhaust brake is hanging up and choking off the exhaust. There is an easy way to check. Remove your engine cover in the bedroom, not the one in the closet. The exhaust brake will be right there, but hard to see because of a tin heat shield.

Take a measurement of the exhaust brake arm where it meets the exhaust brake actuator, noting the position. Drive the coach and when it quits acting up, check the position of the actuator shaft and brake arm and see if they're in the same position. If they're not, you have a stuck exhaust brake flapper.

Here's why I think this could be your issue. My 05 Diplomat came from the factory with the exhaust brake not working. My coach would downshift, but the exhaust brake flapper never closed on the exhaust brake. Many hours were spent and a resolution could never be found. I eventually wired a second switch to the exhaust brake so I could activate manually. This basically gave me a two speed exhaust brake. If I turned on the OEM switch, the transmission would downshift. If I wanted more braking, I would turn on the second switch, closing the exhaust brake flapper.

On occasion, after using the exhaust switch that closed the exhaust flapper, I would forget to turn it back off when I came to a stop. The minute I tried to accelerate, the coach would fall on it's face and a huge cloud of black smoke would be produced because the exhaust was essentially plugged/closed. This is what makes me think you might be having a mechanical, sticky flapper issue. Once it warms up, the flapper fully opens.

[lanerd]

You need to talk to Brett Wolfe (Wolfe10). If he doesn't come on here real soon, send him a PM. He is our resident diesel expert.

Ron

[ScottG]

Doug E. wrote:
ScottG, Cummins is thinking it's electronic or electrical since it fixes it's self when the ignition is turned off, and then refired.

I understand but they should be checking rail pressure at a minimum when it acts up. This is done on your eng with a simple scan tool. (In fact, you could buy a cheap scan tool to watch it yourself)
RP is a critical indicator of the health of your injection system.
Good luck and I hope it's a cheap fix! 🙂

Scott

[Doug_E_]

ScottG, Cummins is thinking it's electronic or electrical since it fixes it's self when the ignition is turned off, and then refired.

[Doug_E_]

Went by Cummins Pacific formally Cummins West. They are going to re-flash my ECM to the latest upgrades. If that doesn't fix my problem they are going to install a data recorder.
I'm to hit the cruise control multiple times when the problem is occurring.
So next week I will take it in, it's a start and Dennis in service thinks the re-flash might fix the problem.
I will follow up on this post when I get home from Cummins.

[ScottG]

Have they checked:
Lift pump pressure?
COV operation?
Rail pressure?
Injector return rates? (If high, DO NOT allow them to replace injectors without first re-torquing the cross-over tubes to see if this fixes the problem. More often than not they replace injectors and have to then torque the CO tubes leading one to think the inj. fixed it when really it was just the tubes).

Personally if it were mine I would torque the cross over tubes and see if that fixes it (very common). If you do it yourself it's just a matter of an hours labor.

[mmccwill]

Have you tried the iRV2 forum -- There is a very good Cummins Engine forum there -- William Willard