I just got home. I am going to wait until the sun goes a little lower because it is 92 degrees still at 6pm.

I wanted to clarify above that I had no key in the ignition and the headlights were off. When I reread what I wrote, I can see how it would seem I meant the headlines on. But no key and no lights were on.

and I found the green wire inside the vehicle. It is spliced into the one of the wires of the trailer brake controller mounted under the dash.

 

That power take off from the firewall block to the brake controller needs an inline fuse if it does not have one. That circuit can probably supply 50 - 100 amps if shorted.


George

 

there is 12v on the big cable on the solenoid (without the key in the ignition) and ZERO volts on the smaller terminal adjacent to it with the key turned all the way to start.

The wire is a light red color that attaches to the terminal but when I pull on it, I can see it pulling only the purple wire which runs alongside the passenger side valve cover. And since the terminal was a little rusty, to be sure, I slid the voltmeter probe under the purple insulation until I could see wire. It still read ZERO. I placed electrical tape over the small hole.

On a side note, since I don’t use a trailer with brakes, I will be disconnecting that jury-rigged wire off of the junction block.

 

The wiring diagrams that I found for your truck are a little wonky so I dont know the whole starter circuit but we can figure it out. Does that red wire on the starter solenoid go straight up the purple wire by the valve cover or does it stop off anywhere like the side of the transmission?

With everything off test for continuity between the starter solenoid red wire post and the purple wire by the valve cover. You may need to use a jumper wire.

George

 

The red wire moves forward, disappears behind some things on the lower part of the engine, comes up the front of the engine, turns back rearward at the level of valve cover. When I pull on the red wire near the terminal, the purple wire moves quite freely so I must assume it is continuous with the red wire. Testing with the multimeter confirmed that is the same wire.

The large terminal on the solenoid is 12V even with car off. The small one is ZERO Volts with key turned to start.

 

I found a few more electrical diagrams for trucks of your vintage. These show that the main power cable for the starter and its attached solenoid is black and then on that same large stud is 1 or 2 red or rust colored wire(s) that heads up to the firewall (as in your first posts). Then on the small solenoid stud on the starter assembly there is a purple wire to energize the starter from the ignition switch. So you have no purple wire on the starter assembly just a black and red? The red is on the small solenoid stud or on the same large stud with the black starter power wire? The solenoid that you measured is the solenoid mounted on the starter or a solenoid in the engine compartment/fire wall?

How is your starter wiring different from this:








George

 

here are some photos. It is possible that the small red wire that “becomes” purple is one of those fusible links . It is hard to see in there. I will try to take some more photos or a video, but I am running late for work.

 

Lets make sure I understand. The red wire that turns purple is the one by itself on the small post on the right on the starter solenoid? That one should see 12v in the start position but does not. There is continuity between that post and the purple wire above and no 12v on the purple wire above in the start position.

The big post with the black wire should see 12V all the time. The red wire that sits on that same post has a fusible link on its way up to the firewall junction block. If you have 12v on the left post of that block then the link is not blown. The red/purple wire has no fusible link.

Where does that purple wire go following it away from the starter? Is there a "start" fuse in this set up?


George

 

George, see my answers in bold. Thanks for the help. And thanks for giving my teen son and me time to bond on this project.

 

Here's what we know:

You don't get any voltage on the purple/red wire on the starter small right post with the key in the start position but yet you have continuity from that post to the purple wire up top by the intake. That wire should go back to the ignition switch for the start signal. So then that switch is either broken or has lost power for the start leg. You also have a broken fusible link. The question there is 1) why did the link blow, where is the short and 2) is that the leg back to power the ignition switch and there is your lack of 12V in the start circuit?

Those two red wires on the big starter post become three wires and end up:

Alternator
Left post on the firewall block
Ignition switch

The block on the firewall then goes to:

Alternator
Ignition switch
Cooling fan relay
Trailer wiring
U/H light
Blower relay
Aux battery relay

Not 100% sure on all those circuits because I have 2 sets of wiring diagrams and they don't agree so some amount of sleuthing will be required to chase all this down.


George