Code 74 Injector wiring fault HELP!!!

So the engine is an 04 MBN CAT in a KW chassis. We rebuilt the engine and I did an ecm tune from Mr haney, Marine Cam, Turbo, Manifold the works pretty much. Stayed with mbn internals and injectors.

First trip out after the rebuild got the code 74. Brought the truck back in the shop and changed #6 injector. Ran fine for about 1000 miles then gave the code again. This time we found a broken wire on the #6 wiring on the internal harness right by the part that bolts to the injector solenoid so we put the repair kit on and all was good. Did a 3000 miles trip and gave me a code 74 and 73 this time. We found 2 more breaks in the internal injector harness so we replaced it.

Next trip out throws the 74 again. We find the injector wiring hold downs have come loose so we tighten them up and locktite them and at the same time to cover our butts we did jumper wires for the 5 and 6 injectors on the external harness.

The engine ran fine for 10k miles then gives the code 74 again. We can't find anything wrong so we put a new external harness on the truck and change 5 and 6 injectors to rule out the solenoids. After 2 hours of running it gave the code 74 again and since this latest code 74 was coming up we found the engine had to get warmed up before it will throw the code. If the truck is left to cool down it will run fine till it gets warmed up. It will last longer empty than loaded before it throws the code.

We started thinking ecm so we put a different one on and same thing. Our shop, the Kenworth dealership and Finning are all stumped so I am turning to the minds of the forum for help on this I am looking for a direction to take to try and find this gremlin of an electrical problem.

Thanks in advance for any responses.

 

Haven't even got the truck in the shop it has gone to low priority because we have so many other things that need to get done.

 

No one else has anything?

 

We torqued them to the 20 inch/lbs required but that is a good thing to look for thanks. The truck is going back into the shop next week and we are starting over in the diagnosing and acting like we have done nothing to it up to this point and se rechecking what we already think is good to make sure it is good.