Hello,

I live in Cincinnati, and my 1978 F100 won't start. I thought that I'd post a message here hoping that maybe somebody local would be able to offer some repair advice.

My truck was working fine, I didn't drive it for a few weeks over the winter, and it just went completely dead: won't start, no interior lights/no headlights, won't crank, nothing. Based on the advice of some family/friends, I've tried several things: new battery, new battery cables, new starter, new solenoid, and new voltage regulator.

One of the posters on the 1973-1979 F100 & Larger F-Series Trucks forum instructed me on how to run a jumper wire from the solenoid to the battery. My truck will crank when a jumper wire is used.

Looking back, I should have had a more organized plan of attack instead of just randomly replacing parts, but I'm not a good mechanic, and I thought this approach might work.

Anyway, I posted a thread over on the 1973-1979 F100 & Larger F-Series Trucks forum which is still active.


https://www.ford-trucks.com/forums/1...ont-start.html



Thanks for any assistance you can provide.

 

Did you ever figure out the problem?

 

Yes, I was finally able to get the truck running again.

I had to have my uncle, who lives an hour away in Dayton, decipher the wiring diagram for me. I talked with him when I was in town in Dayton for a family event. He is an excellent auto mechanic. I did not understand the wiring diagram.

One of the wires running to the solenoid?, I think it was, got disconnected somehow, that wire's connector fell off somehow which just left a bare wire dangling unconnected to anything, and I did not know where to reconnect the wire. I did not want to randomly start reconnecting the wire for fear of damaging anything.

Anyway, the truck is running fine now, and everything is back to normal.

Thanks for everyones help.

 

I'm having the same exact problem. Could you show me how the wires hook up with a picture

 

Yes, I will post a picture shortly.

This was a very frustrating experience for me, I have no idea why or how that wire's connector just fell off and disconected the wire and prevented the truck from starting.

 

I'm going through the same experience. I've replaced everything but the wiring from the alternator to the voltage regulator. Very frustrating bc like you I have no idea when it comes to electrical.

 

I am sorry that I did not get back to you sooner.

2 pictures:

 

6 wires and cables:


1-3: Side of solenoid closest to battery: positive battery cable, yellow and black wire, and the black wire which is the fusible link.

4. Other side of solenoid: cable running to the starter.

5-6. red and tan/brown wires running to solenoid.


The yellow and black wire is what became disconnected and caused all my problems.


Hope this helps.

 

What does the yellow and black wire connect to be I think that's exactly my problem too? Thank you for your help

 

The yellow and black wire, along with a bunch of other wires in a bundle, runs into the truck cab through the fire wall.

That yellow and black wire must control a bunch of stuff, because when that wire was disconnected, nothing worked at all, the entire truck was disabled by that one black and yellow wire.

I will post more pictures in a minute.

 

In the second photo, my index finger points to the wiring bundle entering the fire wall.

 

 

 

So it connects to the positive side on the starter relay?

 

I do not know what the starter relay is, but the yellow and black wire connects, along with the positive battery cable and the fusible link, to the side of the solenoid that is closest to the battery. I am guessing that side of the solenoid is what is called the positive side of the starter relay.