@DirtDonk Paul, always appreciate the advice as well and that is what I was thinking once I pulled the distributor plug from the coil and saw no spark or crank.
Do you mean that you pulled the coil wire out of the distributor? Or that you pulled the distributor wire out of the coil?
If you pull it out of the coil and it's sparking, albeit not strongly, you might not see a spark. That's because the spark comes FROM the coil. That's why you remove it from the distributor cap instead. Then you can see if spark is coming from the coil, through the wire, to a ground.
I checked the cable already (well I just checked to see if it was getting ~12.5V on the cable from battery albeit and not the actual resistance of the wire) which is why I thought it had to be a bad relay but then was also overthinking it.
Yep, the best test for this kind of think is a "voltage drop" test. I can never remember how this simple process is done, so always have to consult the book. But someone here will be able to lay it out for you.
I was also thinking about checking the cable from the relay to the actual starter but need to get someone to turn the ignition for me.
Not really. You can test both cables (battery positive AND starter) with the jumper cable test mentioned. Clamp one alligator clamp to the battery side post of the relay, and the other to the starter side post of the relay.
If the starter cranks, then all three cables (including the ground cable) are good. The starter is good. And the battery is good. It's a good test!
Then you would just have to figure out if the relay is bad, or you're not getting power from the key to the relay via the Red w/blue "S" wire.
If it doesn't crank couldn't it also be a bad starter motor? Or are they usually pretty reliable since they're just 12V motors?
The old ones were super reliable. The new ones? Not so much...
They still need to be made with quality parts, and to quality standards. That just doesn't seem to happen much these days. And hasn't for the past 20 years or so. It's just that it's been getting so much worse in the last five years, that it's another pandemic of epic proportions!
I will try it out in the morning with jumper cables but just so I understand....to test the starter I could just jump batt (+) -> the starter positive since its grounded to the engine?
Yes. You can do it that way, and use the same jumper trick as a process of elimination as well.
First go from the battery positive to the starter. Keep your hands and hair out of the way of the engine's spinny bits! Chances are very good that it's going to crank, so make sure it's out of gear and you're out of the way!
If that works, your battery, negative cable and starter are good.
Next jump the battery side of the relay to the starter. If that works, then your positive and negative battery cables and the starter are good.
Next jump from the starter relay battery side post to the starter side post. If that works, then the starter cable is also good.
Also, what triggers the ignition coil to fire?
Two things. The power supplied from the key to the positive side of the coil, and the distributor signal to the negative side of the coil
I know it is connected to the starter relay but it is also connected to the ignition switch right?
Yes. The connection to the starter relay's "I" terminal via the Brown wire is to send extra current to the coil while the starter is cranking. Also as a backup in case your ignition switch is one of those that, if you turn the key too far during START, the voltage drops off from the switch.
Does the starter relay (solenoid) act as a relay for both the starter motor and the coil or am I getting something mixed up?
It's main function is to fire the starter. It's backup only function is to supply additional juice to the coil. Again though, ONLY during the start/crank process.
I saw some of the wiring diagrams Steve posted in this thread but was still a bit confused.
https://classicbroncos.com/forums/threads/bronco-wiring-diagram.282228/
Welcome to the club!
With the ignition in the on position, it completes the circuit to the starter relay (smaller voltage ~5v?) & ignition coil essentially energizing the starter relay and coil. When the ignition is turned to start, it completes now a different circuit which makes the magnetic field and engages the solenoid to make the circuit between the battery and starter motor (higher voltage ~12v) so that enough amps can be supplied to move the DC starter motor? Is my logic making sense?
In the ON position, the ignition switch supplies ZERO power "to the relay" for any function. What you're seeing in that 4v should ONLY be on the Brown wire on the "I" post.
The Red w/blue wire should have zero voltage at this point.
The red w/blue wire is hot ONLY when the key is in the START position, and that is what engergizes the relay and lets power from from the battery to the starter motor.
This is when power comes OUT of the "I" terminal to help the ignition. All other times the power is coming to the relay via the Brown wire, but not doing anything because the "I" terminal is disconnected from all other internal parts of the relay. Or is supposed to be, except when there is an internal failure of the relay.
This does happen, but is one of the less common relay failures I've seen.
I guess what I am also confused is what engages the flywheel as well if the solenoid and starter motor are separated?
Nothing. The starter gear is the only thing to engage the flywheel's ring gear.
The relay is the only thing that lets power get to the starter.
The ignition switch (via the Red w/blue wire) is what gets 12v to energize the relay.
The battery and it's cables complete the system.
Hopefully that helps!
Paul
, if you don’t drive it a lot, could just be dying battery. Stuck on charger and see what happens. Or go buy replacement and hook up and see if all goes away, or check if battery connectors have come loose or are dirty, etc...
