Maybe I'm not bright enough to read them properly or I'm having a vision problem, but the electrical schematics that I have don't seem to show where a big, black wire in my engine bay goes.

Please see attached photo for reference.

There's a broken wire that's poking out of the main wiring harness on the passenger side of my truck, and I don't have a clue where it goes.

Can anyone with a 1984 F150 4.9 take a look at their wires in this area and let me know where this one hooks up to? I would really appreciate that.

I suspect it has some importance as the truck is now running rich and the code reader will not work when plugged into the test connection.

Thanks in advance!

The wire in question is circled in red.

 

Does your truck still have the oxygen sensor? I wish my son's 1984 with 4.9L very original engine was here so I could look. Looking at the location, it might also be the wire which connects to the choke heater.

 

Yes, still has the oxygen sensor. It is 100% stock - has all the emission & feedback carb stuff.

But the oxygen sensor is already connected.

Thanks,
Dan

 

What about the choke heater?

 

Yep - choke heater is connected. All the top end stuff that's visible is connected.

That's why this one is such a mystery!

 

I am going to stop guessing as someone will soon have access to a diagram. I am glad to hear that another stock 1984 4.9L is still on the road.

 

Well, I do appreciate your help. Sometimes the most simple things are overlooked - I've done that.

I was hoping that someone with a stocker could take a look at his harness and ID that wire.

I have been tempted to disconnect all of the feedback carb & emission stuff, but it's such a happy runner.

Thanks again,
Dan

 

Keep it stock as long as it runs well. The Ford engineers knew what they were doing. With the feedback system, the 4.9L engine can return good performance and surprisingly good gas mileage, when driven conservatively.

 

I agree with that. Maybe not as ideal as FI, but still runs pretty well.

Thanks again,
Dan

 

My first thought is that it looks like a ground for the computer system and would explain why you can't pull codes from it. But you really need to verify that.

What would help identify that wire is to figure out where the other end connects to.

 

Great thought!

It looks like that wire does go into the cab.

I did pull the connector to the computer (under the dash) last night and briefly looked over the wires there. I didn't see a black wire that looked as hefty as that in the connector - initially. I'll look closer tonight.

One thought I had - since it has a plug that can be disconnected, I was wondering if it went to some component?

Thanks,
Dan

 

Does that black wire have light green dots on it by chance? It looks like it could be the one described on page 10 of the EVTM here:

Grounds - Gary's Garagemahal (the Bullnose bible)

Connector C101 would connect direct to a battery negative pigtail; haven't found Splice 258 yet.

 

I'll check that shortly! For the part that's sticking out of the "loom" or wire protector, no. But I will dig down deeper and report back.

Thanks!

Dan

 

Yeah, unwrp that thing and see to where it leads; I could be way off.

I am mostly remembering my 1986 Tempo that had a computer, one of the main ECU grounds was right near the battery and it wouldn't surprise me if the trucks were similar

 

It must be the ground wire that connects directly to the battery? Connector C101 shown below?



I went back and looked at my own pics...see the thread below, and you can see the exact same wire on the 85 I took apart, but you can't see where it goes...
But I'm thinking it went to the battery or the ALT...

https://www.ford-trucks.com/forums/1...nector-qs.html