Check the firewall plug.  It is to right of the pedal support and separate from the headlight harness plug.  It is not uncommon to knock it loose while messing with the other harness.  The wires in that plug go to the starter solenoid and the coil.

Touch your screwdriver across this two terminals only. Angle the screwdriver so it makes contact with the positive lug and the metal nut on the S terminal.


image uploader

Looks like your wiring at the solenoid is backwards.

Tap the solenoid with a hammer or wrench a couple times

Dys1688 wrote:

50vert - Thank you for catching that!!  I replaced the solenoid this morning thinking that could be the problem as I have test paper work for the starter, guess I need to slow down a tad. So now the wiring should be correct.The lights come back on in the car again, but I still don't get anything when I turn the key. I repeated BobE's instructions, I placed one lead of my test light on the battery side of the solenoid and touched the S terminal on the solenoid. I get a light no matter if the ignition switch is in the on or off position. My assumption is that I should not get a light with the key in the off position but should get a light if the key is in the on position.When I put the new solenoid in the car the power cable did pop out of my hand and slap the top of the solenoid, you can see the scorch mark in the pick, could this have damaged it?

The test light is working as it should, this circuit has nothing to do with the ignition switch being on or off.  The "S" terminal is the power to the solenoid to energize the starter from the ignition switch.  It is only energized with the switch held in the 'start' position.  If you jump (piece of insulated wire, or a screw driver, be careful not to touch any body part) the heavy red wire (from the battery post) to the "S" terminal, the starter should crank.  The other heavy wire on the solenoid should go directly to the starter.  You should hear the solenoid energize by a clicking sound.  You can check it by using your test light, first connect the test light alligator clip to the solenoid mounting screw and touch the heavy red terminal on the solenoid, it should light.  Then put the test light on the other heavy wire and jump the solenoid (heavy red wire to the S terminal) and the light should light up.
Also, verify that your negative battery cable is connected to the engine block, it is usually connected at the front of the block and verify that the engine block is connected to the body.  This connection is usually at the rear of the passenger side cylinder head and connected to the firewall directly behind the cylinder head.

Ok, here's what I tried doing

BobE's suggestions
1. Jump (piece of insulated wire, or a screw driver, be careful not to touch any body part) the heavy red wire (from the battery post) to the "S" terminal, the starter should crank - used 2 screw drivers, suprisingly it  cranked, but only once and then wouldn't do it again, actually startled me. From the sound made, the teeth on the starter didn't engage correctly. I'm sure some teeth on the flywheel teeth were ground down. Definitely going to need to check the starter, but now I know the starter does work. Could not replicate.

 2. You should hear the solenoid energize by a clicking sound - it doesn't make any noise at all when using the ignition switch. Don't know if it made a sound when I used the screw drivers.

2A.   You can check it by using your test light, first connect the test light alligator clip to the solenoid mounting screw and touch the heavy red terminal on the solenoid, it should light - it does.

3.  Test light on the other heavy wire and jump the solenoid (heavy red wire to the S terminal) and the light should light up - it does.

4. Also, verify that your negative battery cable is connected to the engine block - negative wire is there and connected although very dirty/corroded - see pic.

50vert suggestions
While you have the clip attached to the mounting bolt, remove the boot from the S terminal, and probe the boot while the key is in start position, it should light the test light - no lights

 Plug the boot back on, then probe the stud that feeds the starter, while the key is in start position, it should light the test light - Clarification - by this you mean the stud on the starter itself and on the starter side of the solenoid?

Summary
Red Wire connected to S terminal with screw drivers - one crank, then nothing
Red wire to S terminal = lights
Mounting bolt of solenoid to Red wire = lights
Red wire (Battery side of solenoid) to Black wire (Starter side) = lights
Red wire to boot of S terminal with key on = no light


 

Just to clarify, when you probed the metal contacts in the S terminal boot with it removed from the solenoid, and the key in start position, did you have the alligator clip on the mounting bolt of the solenoid to get a ground?
Dan, the brown wire goes to the I terminal.

Last edited by 50vert (7/05/2020 9:56 PM)

You said in your first post the battery sat for a while. Maybe the car got a slow drain on the battery. Did you try to put a good charge on it after getting the wiring changes fixed? A week battery will light that light but won't turn a starter.

Ok, after work I went out and played with the Mustang some more. Here are my findings.

1. Alligator clip on positive of battery, probe on either of the mounting bolts of solenoid = Light, so solenoid is grounded.

2. Alligator clip on mounting bolt of solenoid, probe to inside of red/blue wire boot that goes on the "S" terminal, key in start position = No light. Car is a manual 3 speed, so I don't think I have a neutral safety switch. The firewall to headlight harness is what I just got done replacing, connectors looked good, no connectors or pins were lose, wires didn't have any cuts and were pliable. I did use electrical grease on the connections when I put it back together. Will double check the connections though.
3. Alligator clip on negative of battery, probe on "S" terminal of solenoid = No sound, no light, didn't feel anything. Could this be a faulty solenoid?

4. I did use 2 screw drivers again  going from the positive side of the solenoid to the "S" stud and the starter did engage. However I don't think the starter is correct for the car. Looking under the car the starter doesn't look to be seated correctly, but the bolts are tight.  A little research tells me there could be two possible options, one for a manual and one for an auto. From what I've read auto parts stores could have them listed incorrectly. Not sure how to tell what I've got when I pull it out...any thought on that?

Pic of grounding cable that didn't upload yesterday.


 

Dys1688 wrote:

Ok, after work I went out and played with the Mustang some more. Here are my findings.

1. Alligator clip on positive of battery, probe on either of the mounting bolts of solenoid = Light, so solenoid is grounded.

2. Alligator clip on mounting bolt of solenoid, probe to inside of red/blue wire boot that goes on the "S" terminal, key in start position = No light. Car is a manual 3 speed, so I don't think I have a neutral safety switch. The firewall to headlight harness is what I just got done replacing, connectors looked good, no connectors or pins were lose, wires didn't have any cuts and were pliable. I did use electrical grease on the connections when I put it back together. Will double check the connections though.
3. Alligator clip on negative of battery, probe on "S" terminal of solenoid = No sound, no light, didn't feel anything. Could this be a faulty solenoid?

4. I did use 2 screw drivers again  going from the positive side of the solenoid to the "S" stud and the starter did engage. However I don't think the starter is correct for the car. Looking under the car the starter doesn't look to be seated correctly, but the bolts are tight.  A little research tells me there could be two possible options, one for a manual and one for an auto. From what I've read auto parts stores could have them listed incorrectly. Not sure how to tell what I've got when I pull it out...any thought on that?

Pic of grounding cable that didn't upload yesterday.


 

I think you would be wise to install a new nut on that ground and take some emery cloth to both the cable end - both sides -  and the firewall around the bolt.  That master ground is one of the most important connections in the car.
 

Thanks for that starter tech bulletin Barry. Saved me some time, frustration and cash.

50vert. your information helped a lot, thank you. The starter in the car was trashed. When I crawled under the car I found out that the starter had a hole in it and had a ton of rust and debris.I removed the starter and measured the starter registry hole and then the distance from the engine block plate to the fly wheel ring gear.I order a new starter and it should arrive on the 23rd. I also saved the info and printed it out to keep it with the car, hopefully everything will fit as expected.