CM870 misfire under load

[Rawze]

could be worn out actuators...
info: https://rawze.com/forums/showthread.php?...619#pid619

could be leaky injector(s)...
info: https://rawze.com/forums/showthread.php?...8#pid67948

- And if you remove the guts from the shut-off solenoid, does it run better?. They are notorious for going bad and causing fuel pressure issues. - Th engine does not need that solenoid to shut off properly ... it only serves as a secondary safety valve if one of the actuators is failing.

FYI: If removing the guts of the fuel shutoff solenoid causes the engine to stumble and stutter or not shut off right away when you shut the key-switch off, this is a direct sign of leaking/problematic actuators.


If you drain a bit of fuel from the bottom of the the davco filter into your hand or a freezer baggie..is there any coolant in it?.

And yes,... it is normal for the return fuel to go back to tanks. Those engines returned all return/excess fuel back to tanks (a superior design feature), unlike the newer common rail engines that do not.

Also, if the egr system is disabled,,.. is there a check engine light and fault(s) active for it?. - if not then it had a de-mandate file in it, and its likely a crap one.

And BTW: the boost on an CM870 should hold at about 37~ish psi under full operating load, not 32. ... so its in a silent boost derate for the EGR being unplugged... and if there are no active codes for this.. then its a bad delete for sure, as this is a common sign of crappy programming where things were not dealt with properly.

last but not least, the engine brake solenoids can cause mis-fire symptoms too if they are leaky and/or sticking, etc.