CM870 Smoking Issues

[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!.