I am finishing up the wiring in my 12v cummins swapped '87 F250 that used to have a 6.9 IDI/auto trans. Everything has been identified/wired except for ONE item. There is a single black wire with what might be a white tracer (a lot of the harness got sun faded, so not certain on this) coming out of the main engine bay harness near the passenger side battery as the wire loom comes off of the radiator. It has a round black connector terminated on the end of it. It appears to require squeezing of the lock ring to release the mating end, which I don't have. From my research, it MIGHT be a ground wire for the EEC, but that doesnt seem to make sense this the rest of the harness was made for the diesel engine, which wouldnt have a EEC. Perhaps it has something to do with air conditioning? Neither of my trucks have had all the AC gear.

Apologies for what might be seen as a silly question. My first bricknose was already cummins swapped and this wire wasn't doing anything. Got a cleaner truck to swap the engine/trans into and it came partially disassembled, without the engine/trans. Hoping someone can pop the hood on their truck and see where this wire goes.
Thanks!

 

sounds like either a shorting block for ethanol timing adjustment, SPOUT, (if that applies to your year...?), diagnostic connector for something, or an unused extension harness thing like something optional would plug into it if you had it

 

Hmmm, good guesses! It seems i was onto something thinking it might be for the EEC. Hopefully this post with help someone out in the future, but i think I have this sorted now.
I found this this morning:
https://lmr.com/item/WC8699/83-93-Mu...-Battery-Cable
The round connector is the one that i have the mating end to which is certainly intended to be a ground. They list it as a "computer ground disconnect" and features a ring end that might be for some spot on the radiator support or fender?
Found this thread now knowing the "computer ground quick disconnect" info:
https://www.stangnet.com/mustang-for...cation.909399/
Looks like its actually black/green and doesn't apply in my application being a diesel. I'm surprised that Ford would include this ground in what otherwise is a diesel specific engine bay harness with wiring specifically for glow plugs and whatnot. Oh well, now I know. Ill check it for ground continuity and just stick it to the battery or something.
Thanks all!

 

most of my unused plugs are on the right hand side by the fuse box over there, but ford was pretty into making harnesses modular and im guessing it was to reduce how many different harensses needed to be made. sub-harnesses could be added or subtracted as necessary is the idea

 

well, since an 87 6.9 did not have an EEC, that is not it.
and since it did not have a spout, it is not that either.

 

Small update. I probed it with all the other engine/engine bay wiring in place. It had continuity to ground.
I was auditing my shelves to ensure i didnt forget any components and found what i believe to be the original deisel ground cable. It has a couple leads coming off of both ends.
What i believe all are for:
-Battery ground post clamp
-Block ground loop
-approx 6" Lead off block ground loop location that may go to alternator or something else passenger side of 6.9 (i dont have engine to reference; dont know where the block ground was factory, dont know what components/accessories are on that side)
-short lead off battery terminal clamp side with spade style quick disconnect
-above quick disconnect to loop i believe is for radiator support ground
-second lead of the rad support ground loop to quick disconnect, then to the round connector I was trying to track down. This connects to the engine harness mate that mentioned at the beginning of this post.

Long story short, it seems that this round quick disconnect is intended to be a battery ground. Looking at the above ground cable, it ties into the rad support as well, likely ensuring earth is present for horns and seemingly aids fender grounds as well. I grounded it to the battery and ensured by rad support ground is suitable. No notable change in systems performance, but time will tell as i finally get the truck on the road.