CM871 Timing Actuators

[Bigrigdusty]

Hey all! I have heard very good things bout this forum so I’m hoping you can all help me out. I’m up in Canada and am having issues with my CM871. I have talked to a few good mechanics in my area and have them stumped. These engines aren’t as popular up here.

I thought I’d try here before I end up going to a big dealer or diesel shop as I know most of them will just throw parts at it without actually diagnosing anything and costing me mega dollars. (Very little faith in these big diesel shops, been screwed around lots in the past). Anyways, here is my issue!

CM871 in a 2008 W900L. Keeps blowing BOTH timing actuators. It will usually break 1 bolt out of the two and spit the oring out. It doesn’t matter if it’s hot/cold, pulling heavy or jaking, it will just randomly go when it wants. It’s getting worse now as yesterday I had to put new bolts in it as well as orings 3 times just to get it home.

Have it parked now. Now a little history on this truck:

Bought it 4 years ago from a friend and it had a DPF and EGR delete on it. Tune was from one of the more reputable guys up here and it worked flawlessly for me. I did have to I frame it once after the first year. (20,xxx hours on it I was anticipating that, I did cheap out and put jobber parts in it which cost me down the line.) Fast forward to July of 2023, truck started running rough and hard to start so we did the injector bubble test and it failed.

I threw 6 of them in right from Cummins and the thing run immaculate up until July of this year. Started running rough again when warmed up and it was surging and would snuff itself out at an idle. I had a buddy with some spare metering actuators and we threw them on and it run good for the rest of the month until one day I was going along and it blew a TIMING actuator for the rear bank.

We swapped that out and it made it about a day and the head gasket let go (jobber parts bit me in the arse). Anywhoo, I went ahead and ordered a short block right from Cummins and a new head for it. We dropped it in last month and it run good for a few days. Now it is constantly blowing both front and rear timing actuators. The metering ones are good. Keep in mind it did do this before we put the new engine in. I had a spare IFSM and I swapped the actuators out from it to mine and it didn’t make a difference.

Finally I put the spare ifsm on as well as both pressure regulators, new primer pump and check valve, new gear pump, cleaned and double checked the dampners and blew out my fuel return line. Everything checked out but it did not help. I bit the bullet and bought all 4 reman actuators from Kenworth and threw them on but it’s still doing the same thing. The Cooling plate behind the ECM is free from blockage as well as I checked that and I also did do another injector bubble test and there is zero bubbles on either bank, also did a cutout test as well.

Gear pressure is around 252psi at an idle. I also have tried a different ECM and tune but that wasn’t the problem. I believe I have changed everything I could think of that might be causing this problem. Only thing I haven’t replaced where injectors (brand new a year ago and I had them bench tested before I put them in the short block and they all passed.) There doesn’t seem too be any major engine vibrations as well.

Truck runs great when it’s running. Not hard to start when it’s cold/hot. Fuel is clean as I ran a return line into a pail and i cut open the fuel filters (Donaldson is what I run.) I’m hoping someone can help or at least point me in the right direction. Like I said, I am worried about taking it in to a shop in the city as I know they are just parts changers and I’m already in the hole with this unit. Today I believe I’m gonna hook up a manual gauge and go for a drive and see if there is any pressure spikes. Any help is appreciated as well. Thanks for your time!