So I acquired an '86 F150 4.9L V6. The previous owner ripped out the computer to make it more like an '85, or so he says. When I test drove it the truck turned over and cranked right up. After that initial test drive the battery died and the owner started unwiring some wires. Now I have to "hot-wire" the truck in the engine compartment to get it started. Currently I press the yellow (hot) wire, the red/blue starter wire, and the black wire to get the truck started. I'm wondering if anyone has any suggestions or ways to make it so I can crank the truck normally? I've attached photos and the wiring diagram from the Haynes manual. Any help is appreciated!!

 

I am guessing this is a straight six 4.9 / 300 motor?
Think he was trying for pre feed back setup?
Is this a auto or stick truck?
Can you post up a full picture of the engine bay so we can see what you are dealing with?
Dave. ----

 

Hey Dave,

Thanks for the response. Yes its a straight six 4.9/300. I don't know what he was doing honestly lol. It's a manual transmission.
Here are some more photos.

Pete

 

Ok some one has done the feed back removal so that's a start.
I will have to read back through the first post now that I know what we are dealing with.
I am at work so may be a bit getting back.
Dave. ----

 

That yellow wire is for think trailer tow relay.

So dose the truck turn over with the key but will not start/ run?
Or you need to short all them wires to crank & run?
Trying to see where the power stops going to things.
Battery is fully charged right?
Dave. ----

 

Start with getting a pic of start relay to see what and what is not there and find out wire is feeding the HEI. From there, the rest will be easy.

 

Hey Dave,

Thanks for the info. I'll do some searching about feedback removal as well.

Pete

 

Where is that red/blue wire that you are touching to make it crank? On the driver's side inner fender?

I see it now in the picture above. That originally went to the ignition module. You are backfeeding that wire to make it crank. You might have a neutral safety switch problem. That red/blue comes from the ignition switch, hits the neutral safety, and then goes over to the start solenoid. They have a splice along the way that split it out to the old ignition box. That is what you are messing with.

And where does this black wire lead to?

The black wire is a curiosity. It may not be factory. I would try to trace that out to see where it goes.

Sounds like you have ignition power if it keeps running after you pull these wires off after it starts correct?

 

I was at work on my phone between off loading jobs so was hard to see and answer.
Yes if you can get a picture of that area & solenoid.
Do any of the dash lights turn on when you turn on the key?
Trying to see if we are getting power inside or not and the power comes from the solenoid area.

Where in NC are you located?
Would it be close to Raleigh area by chance?
If close it would help if I could see this mess in person LOL

I know you are new but if you go down farther on the main page you will come to chapters and if you go into the Southern one you will find NC chapter.
Being this virus thing is starting to ease up we meet up for dinners, We have one tonight 6:30 at the BBQ Lab on NC 210 in Benson, its just off exit 319 of 40.
Dave ----

 

Hey all. Here is a pic of the starter solenoid. The red/blue wire comes off of it. A wire also goes to the battery and one to the starter motor. Yes the wires I am touching together are above the drivers side fender. I touch all three wires together to start the truck, but once the engine is engaged I remove the red/blue wire.

Pete

 

Hey Dave, I'm in eastern Greensboro. About 45 minutes from RDU. I'd love to come, but I'm actually headed to Topsail for the week!

Pete

 

Going to need yo uto pull off some of that wire covering as it is hiding wires (I hope) we need to see.
Mainly the covering with the wire going to the large stud the battery + is on.
There should be 2 or 3 wires on that same stud.
The wires should have what is called fuse links. They are short wires that would blow if there was a issue but they would not blow if that wire has a spike over its rating, also called a slow blow if it was a normal fuse.

Also do you know where the 3 wires you short together got cut out of so they can go back together?
Well I know the yellow wire so thats ok but the other 2?
I did not know the blue/red to the solenoid came out of the harness on the other side.
Dave ----

 

If it helps, here's my 86' with a 302 EFI.

 

So if you disconnect the black wire the engine shuts off?

 

Thanks Max, I thought it had 3 wires

I was wondering if the red/blue wire was a back feed to the IGN box.
I also dont know if this is a auto or stick and if stick if it would have a clutch pedal lock out on a 86 as my 81's did not.
It also sounds like if the black wire is not powered from the heavy yellow the motor will stop. Yep we will need to know where that black wire is spliced into.

Pete, no problem we will have more dinners and maybe a little closer to you as we do move them around.
Enjoy topsail and we will be here when you get back to help figure this out. I think if it was not for the PO doing what he did with the "hot wiring" it would be an easy fix.
Dave ----