CM870 Smoking Issues

[Lonestar10]

my dads was doing this at idle his idler gear between the cams had the bearing go out and knock the cams out of time. pin the engine get out your wedges and check the cams if their out they either slipped or something made them slip. we did actuators, wiring harness before finding this issue thing is truck was running great he was getting his best fuel mileage but it was wrong.

[hhow55]

(02-16-2020 )Submariner Wrote:  I ran the overhead again to check it two weeks ago (including injectors). Didn't seem to make a difference. Block valve? As in the cartridge valve in the IFSM right by the fuel return line?

Yes the one on the ifsm, and if you have 2 fuel tanks there will be a splitter block valve on the return fuel line. I've had this splitter block valve go bad in the past, resulting in the engine surging.
Also, you mention popping. This could be your egr cooler plugged up with soot.

[Chamberpains]

This could also be a mechanical problem with the EGR valve. I'd pull that off and give it a thorough inspection. It maybe opening or allowing EGR gas in to the system when it's not needed.

When you get Insite up and running you'll be able to monitor fuel pressure and temps. My operating fuel pressure hangs at the 270 +/- (8) or so psi. Its perfectly normal for your fuel tanks to be warm.

Also PM Mommaburt or Unilevers up to see if they can get that "cold weather bug" fixed. I've asked about it and Uni says he has a fix for it. He says its something that Cummins just gave up on because of the age of the engine. They just kind of let that go in the programming.

[hhow55]

(02-17-2020 )Chamberpains Wrote:  This could also be a mechanical problem with the EGR valve. I'd pull that off and give it a thorough inspection. It maybe opening or allowing EGR gas in to the system when it's not needed.

When you get Insite up and running you'll be able to monitor fuel pressure and temps. My operating fuel pressure hangs at the 270 +/- (8) or so psi. Its perfectly normal for your fuel tanks to be warm.

Also PM Mommaburt or Unilevers up to see if they can get that "cold weather bug" fixed. I've asked about it and Uni says he has a fix for it. He says its something that Cummins just gave up on because of the age of the engine. They just kind of let that go in the programming.

This could also be a mechanical problem with the EGR valve. I'd pull that off and give it a thorough inspection.

If this the problem, along with diesel smell you mention. This certainly could cause a surging issue.

[Rawze]

surging idle + 'pop'/backfire issues + fuel/white smoke issues all point towards a few possibilities.

* turbo possibly getting stuck in full closed position, choking exhaust manifold badly.

* Some kind of injection timing issue, perhaps a failed timing actuator, air in the fuel getting into the timing actuator ciscuits (bad injector or air in fuel suction line somewhere, or gear pump sucking air).

* EGR valve stuck in the open position badly.

* crank and/or cam sensor (or tone wheel) problems.

-- To eliminate the egr valve possibility, remove/disconnect the EGR piping at the intake side of the engine to see if it clears up. Also, simply unplugging the 'EGR temperature sensor' should shut off the EGR valve, so this can be done while engine is idling, and checking for egr gas flow coming out while the intake egr pipe is disconnected. There should be very little to none coming out of the pipe at idle with that sensor unplugged.


-- To eliminate the turbo possibility, unplug the air line going to the actuator and move it up and down by hand, ensure it is not stuck while it is acting up.

-- NEXT< you said you went all out with the inframe.. maybe check the tone wheel at the front of the crank to ensure it did not somehow come loose from the crank. There should be zero play in it whatsoever when pushing on it hard.


I have seen it before. Can pull the pan off it and check for any play in the tone wheel to the crank while the pan is off it.
at 4:50 in this video, I talk about it...





-- Next, if the crank and cam position sensors are old or are suspect, replace both of them. - Cheaper than digging deeper into it, and guessing at more expensive things.


-- Next, put the wedges, one at a time into the overhead cams and bar the engine gently back and fourth until they are fully seated (doing only one at a time), then see how close the "Insert Pin" mark aligns with the mark on the gear cover for each of them. Any more than about 1/16" or so off, and something has slipped, or was not done properly during the assembly.

-- After verifying the mechanical tone wheels, sensors, etc... To find out if it is a timing actuator or injection timing issue, do a cylinder cut-out tests while it is acting up. shut off the front 3, then the back 3, and do one cylinder at a time if possible.





-- Next -- Take something and smack the top of the ECM downwards a few times (almost hard enough to dent the casing) to see if it acts up (or stops acting up).. sounds silly, but it is a known issue with them to have a component inside them that gets loose inside them, even on a reman they can have this issue sometimes..


Also, did you replace the crank shaft damper?- to reduce enigne vibration and prevent stuff ftom getting damaged/chaffed, or worn because of excess engine vibration?

And Next -- You can pressurize the fuel tanks to 10 PSI by pinching off the bleeder tube on one fuel tank, and putting a bit of shop air on the other tank, and see if the problem clears up after a few minutes, or if you have a fuel leak in a suction line. DO NOT ATTEMPT TO REMOVE THE FUEL FILL CAP WITH THE FUEL TANKS PRESSURIZED. That cap can hurt a person badly if it blows off there with only 10 psi on its backside!.

[Submariner]

First off, thanks guys for taking time to reply! @hhow55 I will change out the block valve and see what happens. I only have a single 75 Gal tank so no splitter valve to goof up. @lonestar10, I will definitely pin and re-wedge the cams again, just to verify nothing slipped. @chamberpains, is it possible to have a EGR valve that acts erratic after a few hours of heat soak and engine idling without flagging the check engine light? It acted up very mildly today while idling while offloading so I took the few minuets I had, unplugged the EGR temp sensor, while running, pulled the pipe of the mixer connection and really didn't feel any exhaust flow coming out. All the while she continued to smoke white and stink like raw fuel. @rawze, I have changed the crank and cam sensors, I have not revisited the tone wheel yet. I'm going to service it Saturday and I'll take the opportunity to drop the pan and verify it. I will try to get to the turbo next time it acts up to verify that as well. I did replace the vibration damper during the overhaul. I saw it was recommended to do so on here. I was hoping it would act up when I got back to my shop today and pressurize the tank to see what happened but she was burning perfectly clean. Once I get insight back up and running, I will definitely try a cut out test when it acts up. The gear pump shows no external signs of leakage, the engine doesn't "make oil" so I'm assuming that when a pump starts going bad they suck air on the internal side or leak fuel into the oil? I have PM'd Unilevers several times about the cold weather issue but I can't seem to get a hold of him for advice on that or a fix.

[Brock]

Weak fuel pump? Sounds like a issue I had on my cat, it would pass a fuel pressure test at idle but when they bench tested it, it had no vaccuum.

Could also be a turbo hanging up or the egr valve being stuck as already mentioned.

[Lonestar10]

EGR is electric it could be good cold and get goofy when heat soaked

[Rawze]

(02-17-2020 )Submariner Wrote:  ...I have PM'd Unilevers several times about the cold weather issue but I can't seem to get a hold of him for advice on that or a fix.

should also PM mommaburt.