Oil and Excess Pressure in fuel

[Rawze]

(my thoughts)...
== Sounds like bad de-mandate programming as part of your issues.

== What micron filter are you running in the Davco? (fuel water seperator).... if its greater than 10 micron then your wasting your time, as ashpaltine (black fuel) will build up in the fuel tanks making it turn black.

AND WHY WOULD YOUR OIL BE SO BLACK (even if it was getting into the fuel) IF IT IS DE-ANDATED???... unless you had bad programing or you were not changing oil often enough vs. your fuel mileage?

the CM871's cannot be compared to newer common rail engines either. There is a lot of return fuel to the tanks, and they have higher asphaltine buildup especially if your dumping in B20 (bio blend) fuel into it.

- Also, unlike newer trucks.. ALL of the fuel that is not used by the system goes directly back to the tanks after running thru the head, ecm, IFSM, etc.. and this makes the tanks stay at close to the same temp as the coolant + have more ashpaltine buildup (making the fuel black) if you don't filter the fuel very well (10 micron filtration or less)!.

Newer enignes do not do this, so it cannot be a comparison.

The fuel tanks being warm (at or near the coolant temp) is 100% normal for trucks with CM570, CM870, CM871's in them.

The fuel tanks getting black is a matter of proper filtration and staying away from bio-diesel as much as you can + ensuring the injectors are not leaky .... (mentioned below) ...


SENDING FUEL SAMPLES TO A LAB WILL TELL YOU THE ACTUAL PROBLEM!!!... NOT GUESSING AT IT LIKE A FOOL!.

FOR ALL ANYONE KNOWS, IT COULD BE ALGEA OR ASHPALTINE, COULD BE OIL, WHO THE HECK KNOWS!. Wasting thousands of $$$ by throwing parts and guessing blindly is a clear sign of someone not knowing what the heck they were doing.

And if pressure is building in the fuel tanks... then the breather tubes are partially clogged. That, or your injectors are so leaky that they are back-feeding combustion thru the fuel system badly (also makes engine run poorly).

which brings me to the next statement...

- It must have been some kind of moron does not know how CM871's work to troubleshoot this ... because they should have done proper injector leak tests to ensure the injectors were not leaky / combustion gasses were not back-feeding into the fuel system etc.. instead of blind-man throwing expensive injectors and heads at it like a complete fool!. - What a waste of moneys.

CM871's will also have leaky injectors if the damn overhead valves (injector rockers) are simply out of adjustment too!. I have seen mechanics that were so da%mn dumb in the past, that they would set the injector rockers at 0-N_m (or use a gap) like the old big-cams engines of yesteryear, and then wonder why the engine has all these kinds of issues.


For all anyone knows.. it still could be doing this.. as you did not mention ANYONE doing injector tests BEFORE ... OR ... AFTER all that $$$ was replaced!.
REF: https://rawze.com/forums/showthread.php?...8#pid67948

and yeah.. after-garbage injectors and after-garbage head = nothing but problems!. Plain as that, so you wasted all that moneys for a half-arssed repairs and red-neck garbage,.. and so you end up with half-arssed engine run quality is the result.

- As well, the head likely never had to come off it to begin with. There are kits available to replace leaky injector cups to stop the coolant leak. Its worth doing this if the head and engine have a lot of miles on it vs. tearing into it, ... and then to ensure that the leak does not return, it could have been switched over to a zero-pressure coolant system to boot.