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ISM Cummins CM875 Power surge - Diesmandrew - 04-01-2021
Hello, I am new to the Rawze community.
I have an ISM Cummins CM875 That has a power surge that is very noticeable when accelerating. When watching user fueling state I can watch that the Fueling state will change from maximum fueling to EGR flow derate. I have performed the EGR and Turbocharger tests using insite and it passes every test. I originally had a code for the EGR position sensor Data erratic, but replacing the EGR position sensor and pigtail resolved that code, but not the power surge concern. I have replaced the EGR Delta pressure sensor with the updated sensor and removed the pressure tubes and cleaned them. Back pressure tube is also clean and data appears to be accurate. (have not replaced the Back pressure sensor.) When driving the truck EGR delta pressure sensor will read between .5-2.4 inhg.
Does anybody know what The Delta pressure should be, or suggestions to locate the problem.
Maybe this problem has already been answered on another thread and somebody could point me to it.
Thanks
RE: ISM Cummins CM875 Power surge - hhow55 - 04-01-2021
When mine surged in the past, it turned out to be a bad block valve on the fuel return line to the tanks.
RE: ISM Cummins CM875 Power surge - Diesmandrew - 04-01-2021
Was it a quick surge that you can hear through the turbo as well as feel.
I forgot to include the truck.
This is in a 2006 international 8600.
RE: ISM Cummins CM875 Power surge - Nilao - 04-01-2021
Unplug the egr valve and road test, if it still acts up then install a mechanical fuel pressure gauge and make sure the pressure is about 120 psi at 1200 rpm. I would also check for aerated fuel, but you need to install a clear test line between the suction line and pump for that.
You could just put a block plate at the mixer pipe and not allow any egr gas into the intake and see if the surge goes away.
I think the ISM 875 suffers the same flaw the ISX 870 had. The EGR actuator motor is on the hot side and burns out yearly. I'm thinking the valve is stuck open and allowing egr flow when it should not be allowing any. The ecm sees the flow and flags the derate. Just my gut feeling here.
RE: ISM Cummins CM875 Power surge - Diesmandrew - 04-02-2021
(04-01-2021 )Nilao Wrote: Unplug the egr valve and road test, if it still acts up then install a mechanical fuel pressure gauge and make sure the pressure is about 120 psi at 1200 rpm. I would also check for aerated fuel, but you need to install a clear test line between the suction line and pump for that.
You could just put a block plate at the mixer pipe and not allow any egr gas into the intake and see if the surge goes away.
I think the ISM 875 suffers the same flaw the ISX 870 had. The EGR actuator motor is on the hot side and burns out yearly. I'm thinking the valve is stuck open and allowing egr flow when it should not be allowing any. The ecm sees the flow and flags the derate. Just my gut feeling here.
I have removed the valve and the valve seems to work properly off of the truck, plugged in and actuating the egr valve open and closed with cummins insite. And i dont have any missmatch correlation codes with the EGR position sensor.
But with that being said, have you had issues with these folowing the commanded egr position according to the position sensor, but still not opening correctly while in operation?
RE: ISM Cummins CM875 Power surge - Diesmandrew - 04-05-2021
Update on my power surge for anyone else that may come into this concern.
I replaced the turbo after checking everything and that resolved to power surge concern.
Thanks guys for your help.