CM870 Smoking Issues

[Submariner]

Hey guys, I’m having an issue thats making me pull my hair out. Long winded story but just not making sense. I have a 07’ KW T-800 heavy spec remote controlled slinger truck. It has a ISX CM870, CPL 8519. (mid 06’ build). My trucks do some severe PTO hours. It’s a local Seattle truck that sits in stop and go traffic all day. The chassis has 130k mi, and last April I overhauled the engine myself using Rawze/Quickserve guidance at @ 30K hours due to increasing blowby. I used genuine Cummins parts on everything. New as much as I could get, reman Cummins on what I could not get new. The only thing left “original” was the block, crankshaft and camshafts and gear fuel pump. Anything else from EGR components to ALL sensors (including low coolant and fuel pedal potentiometer) have been replaced. If it could be unbolted, it got changed. No expense was spared on parts. Every sensor tube was cleaned and inspected. All parts and pieces installed myself. All summer long, the truck ran just amazing. Low fuel consumption, incredibly smooth power and idle, zero oil consumption, no smoke. A few weeks ago it started acting up. For the first 4-5 hours of the day it would run just perfectly fine 90% of the time from cold start thru warmup and hauling several loads. About once a week on cold start up, with or without the engine heater plugged in, it will cough and hack then start missing or surging up and down by several hundred RPM’s. If you give it some fuel it will immediately smooth out, or let it lope and it will smooth out on its own after about 30 seconds and idle smooth as can be. When it has a “poor” cold start, it will also make a “pop” sound like a gas engine backfire through the exhaust. Almost like clockwork around noon everyday, it would start dumping bluish white raw diesel smoke from the exhaust and just reek of unburned fuel. It would start shaking when doing this at idle, but yet never sound as if it was missing or anything is wrong with it. The instant you give it fuel it immediately clears up, sounds good and all smoke goes away. The only other time that it smokes is going down the road, on a mild down hill when the throttle is basically at an idle but just before the jakes would engage. Touch the throttle smoke goes away. Activate the jakes, smoke goes away. Under power or just a light cruise, no smoke, cleans right up and runs excellent. Sometimes I can leave it idling for hours and burns perfectly clean and clear. Other times it just starts belching white/blue raw fuel smoke, cleans itself up and burns clear or might just “cycle” between raw smoke and burning clean. If i throttle up to 1400 RPM, (via remote, like when I really need to throw material out far, the smoke clears and she just sings). The ECM was changed as well, most current Cummins software installed. The ECM shows absolutely nothing wrong code-wise when plugged into insite (I borrowed a friends set up). I also bought the inline 5 that was suggested on this site and a laptop specifically for only engine use but can’t get past a certain part of the installation if you know what I mean. (if anyone wouldn’t mind helping me get past that I would be much appreciated!). It also suffers from the Cummins “cold weather bug” for boost pressure in the winter. Things that have been checked by myself and re-verified: All wiring harnesses have been pinned-out and continuity checked. Engine, as well as cab to engine wiring. Engine grounds. Charge air system thru engine maintains 30 PSI of pressure (no loss). Cooling system pressure maintains 20 psi overnight. Pinned and re-wedged cams. Verified 4/6. All rocker detents hold tightly. Cams still show no visual wear. Rechecked sensor tubes all clear there. Clear on injector bubble test. No turbo slobber. All actuators replaced and checked per Rawze instructions. IFSM check/relief valves clean and smooth. Replaced the fuel cooler and all fuel lines, has good return flow back to tank. It’s like the computer has a timer saying its been 4-5 hours of work, time for a smoke break and it’s driving me mad that something isn’t perfect with my engine. Any suggestions, criticism or otherwise would be appreciated to help get this stinker sorted out.

[hhow55]

Being you smell diesel in the exhaust and since you truck doesn't have the doser injector, I say you have a leaky injector. When you do the injector leak down test are you doing it exactly as written in the service manual?. Try cranking the engine first, and see if bubbles appear.

[Submariner]

I've followed the manual exactly as written. Yet I still get nothing. I am wondering if a injector can be perfectly normal for the first few hours of the day? Even though the engine has been pulling and at full operating temps for a few hours and then start leaking/screwing up?

[hhow55]

Very possible. Check temps on exhaust manifold, by each exhaust port on head with motor running about 1200 rpms, once the motor is warmed up or starts acting up.

[Submariner]

I have also been wondering... Other than the occasional surging issue and rough start when cold, if fuel temp might be affecting the injectors. I have a single 75 gallon tank, with fuel cooler. The tank will get decently warm to the touch when idling onsite and not moving after a few hours. Even though the injectors that were installed were Cummins "PX" would fuel temp make a bad injector start sticking or leaking even though the water temp and oil temp are normal and the engine has been running for a half a day?

[Submariner]

I did that as well... When the engine is not acting up at idle (675 Rpm), each exhaust port shows about 350 give or take a few degrees with a infrared thermometer. When it does act up, it shows the same dang temps at the exhaust port.

[hhow55]

When was the last time you ran the overhead, cause it is necessary to that before doing the leak down test,

[hhow55]

Other than the occasional surging issue

Change the block valve on the fuel return line..

[Submariner]

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?