Cummins ISX CM871 Technical discussion

Discussion in 'Trucks [ Eighteen Wheelers ]' started by Rawze, Aug 13, 2013.

Thread Status:
Not open for further replies.
  1. Rig Wrench

    Rig Wrench Medium Load Member

    Messages:
    393
    Thanks Received:
    57
    Joined:
    Dec 24, 2010
    Location:
    northeast
    What exactly does the delta p sensor read? And on the egr temp sensor what does it do weather the sensor reads hotter or colder?
    Thanks for all the input
     
    Rawze Thanks this.
  2. jonkaj

    jonkaj Bobtail Member

    Messages:
    2
    Thanks Received:
    0
    Joined:
    Sep 3, 2013
    Can someone help me,
    I have 2005 Volvo ISX 780 and is overheating when in idle and in reverse.Took it to mechanic and changed thermostat and is still doing the same thing, cant find anything that is wrong. Any suggestions what can be wrong with it?
     
  3. deming807

    deming807 Medium Load Member

    Messages:
    350
    Thanks Received:
    96
    Joined:
    Jul 31, 2013
    Location:
    Summit IL
    Did you ever change the radiator? Do you have cap on it? Did you ever add stop leak to it? Did you change water pump? Is radiator fan working properly?
     
    Rawze and cumminspwr600 Thank this.
  4. daf105paccar

    daf105paccar Road Train Member

    Messages:
    1,665
    Thanks Received:
    777
    Joined:
    Apr 15, 2012
    Rawze,what do you concider a good bypass system?
     
    Rawze Thanks this.
  5. Rawze

    Rawze Medium Load Member

    Messages:
    329
    Thanks Received:
    750
    Joined:
    Jun 29, 2013
    Location:
    inmytruck
    The Delta-P sensor is actually named 'Exhaust gas Differential Pressure Sensor' I think. Delta-P is just a shortcut name for it (Detroit uses that name for them). It actually reads the amount of 'flow' inside the pipe that sends exhaust gas back around to the intake. How it works is that there are actually 2 pressure sensors inside it. One further up the pipe from the other (hence the 2 connecting tubes going to it). The signal sent to the ECM is the 'Difference' between these two sensors only. Basicly its a fancy name for a 'Flow Sensor'.

    The EGR Temp sensor on the CM870 and CM871 is located in different places depending on year.style of your engine, but is the same for all of them. It tells the ECM how hot the exhaust gas is going from the exhaust back into the intake. This is important for the ECM to know because gas that is heated, or hot, is expanded gas. Between this Temp sensor, and the Flow Sensor(Delta-P), the ECM can then determine the proper 'Mix Ratio' of clean air coming from the turbo and Dirty air coming from the Exhaust. It is that proper ratio of clean/dirty air that determines how much of the NOx, and other bad gasses are produced during combustion. This mixture is monitored by the Delta-P AND the Exhaust EGR Temp. sensor together so that the ECM can control the EGR Valve properly. This means if either of these 2 sensors are reading wrong (from soot build-up), the EGR valve goes somewhere it shouldn't, creating symptoms as mild as lowered fuel economy, to as extreme as EGR Valve failure codes, excess soot (leading to DPF Problems), low or poor power from the engine, rough idle, and indirectly sometimes, ghost turbo/actuator problems.

    The EGR Temp sensor itself is programmed in ALL the CM870 and CM871 engines to 'SHUT DOWN IMMEDIATELY THE ENTIRE EGR SYSTEM', and run the engine normally without EGR, closing the EGR valve completely if the temp sensor it is shorted out, grounded out, or otherwise just simply unplugged. This means that it is quite easy to disable the EGR on an ISX CM870 or CM871, except for 2 other problems that can/will happen. The First Problem is the fact that the engine will complain about it being unplugged/shorted/etc. by turning on your Check Engine Light (yellow triangle) on ALL trucks for both the CM870 and the CM871. The second problem is a much bigger problem. Each of the truck makers Volvo,International,Pete, and others, have different software in them custom to that maker/engine model, and some of them are programmed to actually shut the engine down if a fault for the egr Temp sensor happens, so that just any joe-fixit cannot just shut off the EGR and run around all day with just the Check engine light on. So far, it seems like from what I have seen, just about ALL of the CM870 engines will not shut down over this, but its a throw of the dice for the CM871. The only brand of trucks that I have seen where you can just unplug the temp sensor on a CM871 so far without ANY consequences (except the Check Eng Light), is international. Peterbuilt, Kenworth, and Volvo trucks will usually just cause an engine shut-down after a very short period of time, if its faulted.

    Variances in the EGR Temp sensor (it working properly), cause a bit more, or less EGR gasses to flow into the intake via adjustment of the EGR Valve. There is however an upper region where the EGR will shut off completely if the temp. is too high, and the sensor is ok. Most trucks are programmed to shut off the EGR if the temp. sensor reads between 230-240c, and to fault the sensor out, if it reads above this. Exhaust gasses this hot will cause the engine to overheat and,or run rough, so the EGR is switched off. This high of temperatures also tho, tell the ECM that the EGR Cooler is no longer doing its job. Because of this, the engine will start to count the number of hours it is too hot, while allowing the engine to run, and when a programmed 'Time-out' has been reached, the engine will go into Derate and/or shutdown.
     
    Last edited by a moderator: Mar 5, 2014
    DocRox, jerrymc, power freak and 9 others Thank this.
  6. Big Lou

    Big Lou Light Load Member

    Messages:
    152
    Thanks Received:
    22
    Joined:
    Aug 15, 2013
    Location:
    Tampa, Florida
    Rawze i am with you as i am an owner operator too. With a few trucks and these dealers need to know that we know what we are talking about when we go in to fight our case. So I think when we go in we should go in armed with this info that you and others have talked about. So we are not being taking advantage of!! If we decide to go to a dealership or amom and pop shop. I have had alot of experience with dealers and other shops if you tell them what you want checked first they will look into it before they will suggest other things thatmight be the problem. But again we need to go in there and let them know what we are talking about so they cant and wont take advantage of us. Thanks Rawze for all your step by step process to pass along to who ever is working on our equipment!
     
    Rawze Thanks this.
  7. daf105paccar

    daf105paccar Road Train Member

    Messages:
    1,665
    Thanks Received:
    777
    Joined:
    Apr 15, 2012
    Rawze,question for you .
    Lets say you want to keep your engine as is,stock.
    But you are not afraid to get your hands dirty and do like it is suggested,keep sensors and turbo free off soot to avoid future problems.
    How would you clean the turbo?
    Use a product?
    Blow it out?
    With the vanes it is not the easiest thing to clean.
    Any suggestions?
     
    Rawze Thanks this.
  8. Rawze

    Rawze Medium Load Member

    Messages:
    329
    Thanks Received:
    750
    Joined:
    Jun 29, 2013
    Location:
    inmytruck
    on the CM871, it will pretty much keep itself clean. The engine performs a 'Cleaning Cycle' every so often for the turbo, and for the EGR valve. Its more eeffective for the turbo than the EGR valve, because the turbo has a high volume of air/exh. gas flow through it, but the EGR valve does not. I haven't seen any turbo's 'Packed With Soot', even after half million miles on them, but I have seen a lot of EGR valves that could use a good cleaning after only 300-400+k miles. The engine will perform a 'Cleaning cycle' at regular intervals, and when the engine is shut down/started, but I am not sure exactly what triggers or disallows it durig the running of the engine. I have seen where the turbo cleaning cycle can get stuck, causing the boost pressure of the engine to cycle up, then down one time at regular 2 or 3 minute intervals before, but it was only because of bad parameters in the ECM.
     
  9. Blind Driver

    Blind Driver Road Train Member

    Messages:
    2,974
    Thanks Received:
    1,334
    Joined:
    Aug 7, 2006
    Location:
    New Albany, IN
    What about doing a "hotrodder decarbonization"?

    I had a car that needed water down the carb every 6 months due to carbon build up. It always ran much better afterwards.
     
    Rawze Thanks this.
  10. Rawze

    Rawze Medium Load Member

    Messages:
    329
    Thanks Received:
    750
    Joined:
    Jun 29, 2013
    Location:
    inmytruck
    ISX EGR tuneup youtube videos,...

    Well, I took some much needed home-time this past week, so I haven't been on the forums much. As requested though, everyone wanted me to make a video on how to do a EGR tune-up, so I did. The truck I did this for wasn't very bad, and we didn't get to do the after-treatment injector, but the procedure nonetheless is described well I think. The fuel mileage gain for this truck afterwards ended up being 0.6 mpg, and it ended up clearing intermittent turbo low-boost alarms as well. Also the HPa reading of the DPF was sitting somewhere around 2.4, and that is acceptable for now.

    The whole thing is 6 parts, as it was about 1.5 hours of video total. For those who were asking, here it is,...

    https://www.youtube.com/watch?v=FhJxpyS5MpY

    https://www.youtube.com/watch?v=IsXEQe54naw

    https://www.youtube.com/watch?v=QNbGbrkg81w

    https://www.youtube.com/watch?v=qMmNMLbdcG4

    https://www.youtube.com/watch?v=imWMqT8nNKg

    https://www.youtube.com/watch?v=1aeNDdSBe4o

    maybe this is helpful to those out there who are having DPF or EGR probelms,...Rawze
     
Thread Status:
Not open for further replies.