I inherited my dad's old truck 92 f150 7.5, that sat around for a couple seasons before they had to get rid of a lot to move to retirement. Prior to this, the truck was in running condition no significant issues.
There was wire damage from mice or rats and while my dad attempted to repair it, there's 3 wires that he could not figure out where they went, but the truck still starts and drives (mostly).

The 3 wires in question are right by the battery and starter relay, one is orange, one is grey (or light grey) and blue (or light blue), and the other is purple and orange (or yellow). pictures attached at the end.

When the wires were originally chewed, most pairs were obvious where they spliced back together but these three i cannot find a connector, a splice, a ring or any component that would be remotely close to that area. I can see they run across the front of the engine bay all the way back to the driver side firewall. the wires only have about 8" of length where they were chewed along with the rest of the bundle so i wouldnt think they need to run very far from that area unless the mice ate vast lengths of the wire away but so far have not found any stray wires the times ive looked at and messed with the truck.

I have the electrical vacuum troubleshooting manual, but I'll be honest I have a hard time making sense of the wiring diagrams and I'm not sure how to use it in this specific case of identifying a color wire in a physical part of the engine bay. It has several issues that may or may not be related. It goes into a limp mode after it warms up and you apply heavy gas until you shut the truck off and restart it and it will be fine, It also has a battery discharging issue so i disconnect the battery regularly. Again not sure if its related or if it helps in diagnosing what these wires are. I'll work on those issues later.

Anyone have any idea on what these wires are or where they should connect? I inadvertently discovered that if the orange and the purple/orange touch the truck dies instantly. Haven't pulled out voltmeter but I believe one of them is hot constantly even without key. I leave them taped up but i know this isn't right and decided to explore if its worth troubleshooting the most basic issues first, this being the main one before i work on converting to 3rd gen Alt.

Thanks for helping/looking

 

Do you mean F250? I don't think the 7.5 liter was available in F150's.

 

If it's a 7.5, one possibility is that it's the O2 sensor wiring.
From Haynes for '92 and later 7.5:

 

Yes sorry it is F250 7.5. So I found that reference in some of the wiring diragrams and maybe I'm just dense to this stuff but why would HEGO wires be running up by the battery when there's nothing to run to in that area? or should there be something there?

 

The word of note is HEATED, meaning that there is 12v power to the O2 sensors.

 

To use my '88 5.0 as an example, the O2 sensor wires run from the passenger's side firewall connector, around to the area of the battery tray to another connector, then originally followed the starter cable, from the fender mounted starter relay, and end up at the O2 sensor.
These harnesses were preassembled, then installed on the assembly line.
Can you see the wiring coming off your O2 sensor, to verify that's where these wires should go?

 

From what I can trace without cutting the wrap the entire way, the o2 sensor plugs into the harness by the transmission. following those 3 colored wires it snakes up through the driver side along with a bunch of other wires, under/through the power distribution box and around to the front of the truck, then over to the battery area, thats where the three wires end in breaks.

 

Are there any empty harness connectors nearby?
This is the O2 plug configuration for my '88. It could be different for a '92. I don't have '92 information.

That was a common configuration for other connectors too, so verify by wire colors if you find an empty one.
Is there any fresh electrical tape that could be hiding the wires you're looking for?
I saw other splices in your pictures. Are they correct by wire colors? It's possible that the wires you're looking for were inadvertently spliced to other wires.
Look around in the truck for an "extension" harness. My O2 harness extension was in the glove box when I bought my truck. My spout connector was in the door pocket.

 

Unfortunately no, there are no open wires or splices, no plugs, fuses anything in that area what so ever. The truck has been my dads since the 90's and up until this fiasco was a daily driver 2 years ago. The wires he did splice back i checked and they match the colors and run back to blower motor and other components terminating in connected plugs with the corresponding color wires none of which match these.

I did check the bare purple/orange (yellow?) and with key in on position its hot, otherwise they are all dead with no key on.

I dont think the 7.5 E40D is the same as yours as the o2 sensor wiring runs from the sensor itself up into the transmission harness and up to the electronics on the driver side, it doesnt run on the passenger side at all.

I'm assuming that pigtail you have goes back to your o2 sensor on yours right?

What im hoping for is maybe someone with a 7.5 intact without too much modification that i could maybe verify match the wiring over there but so far i cant find anything.

I dont suppose anyone has pics of their 7.5 in that area to see if im missing some entire component or fused links or something?

 

Yeah, somebody will be along who has a 7.5 or mechanical drawings.
The picture I took was with the extension completely removed from the harness.

 

I have my '95s entire front body harness available if you want it - I converted my truck to '96-97 7.5L CA-emissions Mass Air SEFI, which necessitated a complete firewall-forward wiring harness for all of the different sensors... Not sure if your '92 is the same as '95, but...

 

here's a thought I had after comparing the wires to the HEGO wiring, since technically all 4 wires exist there O, P/O, GY/LB, BK (not shown it was temporarily grounded off to negative post on the frame). Those are the color coding for the front harness and the HEGO sensor for sure so i don't think we are mis-identifying them and the P/O wire is energized with key on. Was there ever a truck that had two o2 sensors? Or possibly were the wires included in the factory harness but wrapped up where it wasn't visible...until rats ate them free? With the E4OD and 7.5 with the o2 sensor set differently than other models, between the two exhaust pipes just before the cat, the wiring is routed on the transmission harness that runs up to the rest of the loom on the driver side? I'm grasping for a reason why I have my o2 sensor wired in as part of the factory wiring, but also have these 4 wires extra wires for what sounds like a different equipped truck.

 

I don't know, but if you could get that harness from cougrrcj, you'd have a way of seeing what yours should look like.
Haynes shows the same diagrams for '92 through '96.