Cummins ISX CM871 Regen Temps Question

I recalibrated the vgt today it was correct hmmm

 

And still nothing? Did you give us the specs on %Load (especially when fan is locked in)? Have you run the overhead? OOOO just had a thought, have you checked static timing?

 

I did the overhead adjustable a few days ago because it sounded like crap. I also replaced the injector o-rings by his request. Didn't check the static timing. I didn't get the reading of the %load with the fan on, but I will tomorrow. I'm also waiting for someone to send me the AV10224 calibration.

 

If the turbo is clamping down like it should, boost pressure in spec, no EGR flow by passing the valve, I'd be leaning toward a fuel problem. Almost everytime I have the valve cover off on an 871 I recommend static timing to be adjusted as Cummins had a major issue with injector camshafts being set wrong. Not just plopping a 4 and 6 wedge in like setting base timing. I mean actually going through the whole static timing process and getting it to the advanced side of Nominal (not crazy but I shoot for advanced rather than just close to nominal). If unit has had oil filter plugging issues, this will help with that along with greatly helping with regen cycles. Finally if all that is good I have heard of techs plopping in 6-packs (all injectors) but I still havent gotten to that level of repair yet. You still have metering and timing actuators to rule in or out, %load should help identify that.

 

Ill get the percent load tomorrow. Just for fun I uploaded the AV10065.46 that was sent to me and the DOC temperature on this cycle went from the previous 440F to 475-480F and held itself there. If the injector cam is set incorrectly wouldn't it throw a fault code? When I was learning to assemble the ISX at the previous dealer I worked in, I accidentally didn't time the injector cam properly with the wedge and It threw numerous counts of cam position fault codes. I had to take the front cover off & re-time the engine lol. After this AV10224 calibration... I'm going to be clueless on the issue. I heard of these having ground issues since the DOC/DPF temp sensors share the same ground as the ambient air temperature sensor & the coolant level sensor. When I was looking at the parameters I noticed the ambient temperature sensor was disabled. I'm not sure if it's an good idea to just pop in a six-pack If all were trying to do is increase the DOC temperature so the fuel can eventually start dosing. The turbo is the main component helping to create the heat correct? At idle, I did rev the engine quite a few times while monitoring the turbo vane position and it was going around 50% and at idle It would increase again to the 90% range. EGR is also responded commanded & actual when I took the truck for a spin in several gears.

 

To rule out the whole egr system, make up a thin piece of plate/sheet steel and drill two holes in it so you can bolt it in between the egr connecting pipe and the intake pipe. This will totally seal off the egr system. Try that and see what happens. Dumb question, but air filter isn't plugged or anything like that?

 

The air filter is fairly new. Someone on mhhauto told me about the static timing and that 90% of the CM871 were set incorrectly on the injector cam. Samething Strange77 mentioned.

 

"If the Injector Camshaft is set incorrectly wouldn't it throw a Fault Code?"
-No, because the camshaft is a slip fit so there is virtually an unlimited amount of ways the Injector cam could be installed. If you set the camshaft out of time drastically then yes you would throw codes. But we are talking about adjusting the Injector cam anywhere from .25 degree's (1/4 of a degree) to .75 degree's (3/4 of a degree) were talking about moving this thing literally a #### hair lol.

"The turbo is the main component helping to create the heat correct?"
-Sort of, Everything from turbo to metering/timing actuators, to the injectors themselves all play a role in getting the engine up to 550F. Remember when you initiate a regen you are requesting the engine to build an excessive amount of heat at basically an idle. Even if the metering/timing actuators are doing their part and they are working correctly, the fuel injectors themselves can be getting weak and over fueling/under fueling which will effect the regen temps. If the injectors aren't operating correctly then yes the turbo will respond and try to close down more in an effort to create more heat with more back pressure. So you're question is whats happening first? Is the turbo failing causing poor back pressure because turbine gases are flowing through the shroud plate cause its cracked, or is the turbo shutting down farther in order to compensate for the faulty injectors? Or, has the Injector camshaft slipped some in the gear (have seen this, hence the static timing NOT BASE TIMING)? Or has the metering/timing actuators weakened causing the whole fueling system to be ####? Or do you have restricted fuel filters/fuel lines (seen this before as well)?

There's so much that goes in to a successful regen its not as easy as most make it sound. And there is no road test or driving scenario that will point you to anything when it comes to a regen. A regen and monitoring is the only thing that will help you find your issue.

 

Review this and make sure you record the readings as its in regen.

 

Only one that's off is the turbo vgt position which is at 96% on a regen and turbo speed is 39-40k, but I'll double check tomorrow.