Truck Repair: Cummins m11, cummins m11, cam sensor

Question
QUESTION: We have a truck with a misfire and a code ( inj 4 return voltage not dtected) we swapped inj 4 & 1 still the same , tried a different ecm still the same tried new cam sensor still the same , new harnesses ( 1 from ecm to valve cover and one for injectors, checked and cleaned alll grounds , fuses etc. with 4 unpugged it runs a bit better than when it is plugged in do not know why.

ANSWER: hi greg,
the only thing left that i can think of is the plug on the rocker housing....if it is open on #4 then no matter what you change it will always be open. other than that I can't think of what it may be. try and track down a cummins manual and follow the trouble tree...maybe there is something that is being missed.

Good luck

Matt

---------- FOLLOW-UP ----------

QUESTION: Matt
The two harnesses we replaced connect at the rocker housing there is no other plug , they join through the cover , we traced the tree that far then they ask about compression and it seems the same as the other cylinders

Answer
Hey,
If it was me troubleshooting this complaint...at this point I would start from scratch. Unplug the harness at the ecm and find the pin that is for #4 inj. verify continuity right from the injector back to the ecm plug (make sure you are not putting voltage through the ecm!!) while doing so wiggle the wires and the harness. if no issues found try checking the pins in the harness with a small paper clip (or if you have the right tool that would be better) and see if there is a slight drag when inserting and pulling out...check it against other pins and compare, these pins are known for opening up a bit and not making contact with ecm pins. Also..is this code still active after repalceing the harnesses? if not clear it and run the engine...if it doesn't come back then you have solved it when you replaced the harness..etc. find the specs for the injector and check the solenoid resistance. also, some times on the N14 engine the push tubes fill with engine oil and cause timing issues...not sure if the M11 had the same problem. try checking valve adjustment too, there may be a cam or cam follower issue, sometimes the cam followers bolts back off, this would send your timing out of wack.

Sorry I can't be more help,

Matt