solenoid

sixtyfive5.0

Member
Jul 16, 2022
10
2
13
Interestingly my '86 starter solenoid has all the wires swapped? So battery and acc are all on RH post (towards front of car), and the lead to the starter is on left next to shock tower. Isn't it supposed to be the other way around? Anyone seen this before? Been operating fine and looks to have been that way for a long time, but yesterday starter stayed engaged...so got me looking at things.
 

Mustang5L5

Put lubricant all over the balls
Mod Dude
Feb 18, 2001
39,455
15,302
224
It doesn't matter. It's a relay. Your relay trigger is the single red/blue wire on the top post, and the ground is the metal frame to the inner fender. When you apply power to the trigger, the relay closes.

At that point, the two main posts are connected. One main post just acts as a distribution block post. Doesn't matter which side it's on. The other side has the power wire to the starter. Close the relay and both sides are connected and power flows to the starter.
 
  • Like
Reactions: 1 user

7991LXnSHO

wanna catch the space herp
10 Year Member
Sep 1, 2010
7,388
3,090
194
If it stayed stuck, that often indicates a weak or partially discharged battery. For some reason, a weak battery causes the points to weld. A good tap to the top of the relay (solenoid) can often free the points. But the starter Bendix and front bearing does not tolerate being over spun too many times. So get your battery load tested for free at the FLAPS.
Bad connections or corroded cables are other likely causes.
 

mikestang63

SN Certified Technician
Aug 27, 2012
11,291
8,777
214
I would only get a FOMOCO solenoid, as the parts store brands suck. I use original FOMOC ones i pull from the junkyard in my 3 foxbodies for years with no issues and have 5 laying around as backups before I would use a new parts store one.

1659147496625.png


courtesy of our own jrichker

NON mini starter
1659148149809.png



1659147389536.png
 

sixtyfive5.0

Member
Jul 16, 2022
10
2
13
If it stayed stuck, that often indicates a weak or partially discharged battery. For some reason, a weak battery causes the points to weld. A good tap to the top of the relay (solenoid) can often free the points. But the starter Bendix and front bearing does not tolerate being over spun too many times. So get your battery load tested for free at the FLAPS.
Bad connections or corroded cables are other likely causes.
Thank you, I'll check it out.
 

sixtyfive5.0

Member
Jul 16, 2022
10
2
13
I would only get a FOMOCO solenoid, as the parts store brands suck. I use original FOMOC ones i pull from the junkyard in my 3 foxbodies for years with no issues and have 5 laying around as backups before I would use a new parts store one.

1659147496625.png


courtesy of our own jrichker

NON mini starter
1659148149809.png



1659147389536.png
Perfect, thank you, yeah I wired the new solenoid correct handed, but upgrading to mini high torque starter this weekend and will rewire it again :).
 

Mustang5L5

Put lubricant all over the balls
Mod Dude
Feb 18, 2001
39,455
15,302
224
If you have a high torque ministarter, you can ditch the factory style solenoid and just install a distribution block and wire in a simple Bosch style relay to activate the mini-starters relay. You can carry an extra relay in the glovebox if the Bosch relay ever fails.


Ford is essentially doing the same on the 87-91 cars by using one post of the solenoid as a distribution block. You can use the small post's blue/red wire as a trigger for the Bosch relay and just run a #10 wire down to the starter to trigger it from the relay.

1659620281093.png
 
  • Useful
Reactions: 1 user

manicmechanic007

5 Year Member
Sep 26, 2017
1,902
537
133
They told us in screwell that there is a diode in the Ford ones that does something and they showed us the difference on an oscilloscope
Seemed at the time to be the difference of a gnat on a rats asss
You have to watch the alternator pattern on an oscilloscope to see the difference so wrtf
Maybe someone with some brains will chime in
 

General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
23,672
8,754
203
To explain the diode thing as best I can with my feeble brain capacity and limited electrical knowledge,
When a starter, for example is 'de-energized ' (basically releasing the key) the action can create a 'backwards power wave' that seeks someplace to go. Most times it's harmless, sometimes not, that's when the damage will occur,
In the towing industry when the clutch pump replaced the trans driven PTO they found 'power feed back' would energize the belt driven clutch pump at cruising rpm with catastrophic results. The pump is designed to operate below 1500 rpms, imagine the pump running at 2500 rpms. The remedy was to place a diode between the positive wire at the pump to the pump ground wire.
How/why it does what it does is beyond my comprehension, I do know without the diode the pump will energize (most times just for a second or two) whenever the starter disengages (key released).
This is my understanding of the reason for the diode in a automotive electrical system where the current to something like a starter collapses (turned off). Which is oversimplified and prolly not entirely accurate.
 
  • Agree
  • Like
Reactions: 1 users

7991LXnSHO

wanna catch the space herp
10 Year Member
Sep 1, 2010
7,388
3,090
194
To explain the diode thing as best I can with my feeble brain capacity and limited electrical knowledge,
When a starter, for example is 'de-energized ' (basically releasing the key) the action can create a 'backwards power wave' that seeks someplace to go. Most times it's harmless, sometimes not, that's when the damage will occur,…
You are on the right track.
1. I believe it’s the magnetic field collapsing that causes the charge with the windings. 2. If the starter is still spinning, it acts like a generator.

Here’s a similar experiment. The next time you have a box fan in the garage window, and it’s spinning from the breeze but not plugged in, do not touch the plug with your hand. Use meter probes to measure voltage.
 
  • Informative
Reactions: 1 user

7991LXnSHO

wanna catch the space herp
10 Year Member
Sep 1, 2010
7,388
3,090
194
that's what I meant by 'backwards power wave'.
Back in the last century, electricity or electronics class tested us about which way the magnetic field was induced by which way the coil was wound, and a whole lot more about this.
Now, I just hook up the positive and negative wires according to the + and - signs. :D
 

TOOLOW91

If you're the village idiot what's that make me?
15 Year Member
Nov 29, 1999
7,964
7,994
234
If you have a high torque ministarter, you can ditch the factory style solenoid and just install a distribution block and wire in a simple Bosch style relay to activate the mini-starters relay. You can carry an extra relay in the glovebox if the Bosch relay ever fails.


Ford is essentially doing the same on the 87-91 cars by using one post of the solenoid as a distribution block. You can use the small post's blue/red wire as a trigger for the Bosch relay and just run a #10 wire down to the starter to trigger it from the relay.

1659620281093.png
My car has been like this for 3 years now . Not a single issue .