1970 Bronco 302 - Coil Upgrade Question

[tonytony9]

Hi Forums!

I had the Bronco in with my mechanic to help diagnosis intermittent "bucking" at different RPMS and Speeds. Essentially, the Bronco felt like it hesitated and jumpy. Yet, on some rides, I could cruise on the highway for a long ride with no issues. He told me my coil was cracked, arcing off the block.

I believe I had the original coil; yellow top, battery and dizzy post with the stem for center spark plug wire. From what I can read, it says Autolite FAC-12029.

He replaced the coil with a NAPA Echlin IC10.

I am still experiencing the bucking. I was thinking of upgrading to a Petronix from my points/condenser setup anyway. This got me thinking, the NAPA coil is 12V. I am not sure if I am even supplying this coil with 12V since it was a stock setup??

1. How do I determine if the coil is getting the correct voltage?
2. How do I determine what wiring changes I would have to setup in order to get Petronix and/or my current points/condenser to work with this Napa Coil.

 

[Broncobowsher]

This is probably a case where there are multiple issues. If the coil was cracked and visably arcing, yes it had a problem. But that problem wasn't the drivability issue that you went in for.

 

[tonytony9]

This is probably a case where there are multiple issues. If the coil was cracked and visably arcing, yes it had a problem. But that problem wasn't the drivability issue that you went in for.

Yes I agree. I have been tracing down a few potential causes.

Do I have to do any rewiring in order to get the this coil to function properly? Better said, how do I know it is functioning properly given that this is a 12v and I am using the existing (assumingly stock) wiring.

 

[Oldtimer]

Stock wire harness has a resitance wire in it, to meet coil requirements, and the Napa coil you have requires resistor, so it will work.
No mods required.

 

[DirtDonk]

So if you do convert from points to Pertronix, then power the distributor separate from the coil.
The distributor module will want the full 12 V, while your coil wants to see the 8 or 9 V that the resistor wire provides.

 

[tonytony9]

Ok, something very obvious I noticed; looks like my mechanic attached the yellow connector (from the dizzy) to the positive, and the resistor wire to the negative. I believe this is incorrect and should be reversed. I assume this would cause back firing but would it even run?? Or am I missing something here.

Stock wire harness has a resitance wire in it, to meet coil requirements, and the Napa coil you have requires resistor, so it will work.
No mods required.

View attachment 952006

Thank you, wow obviously printed right there

So if you do convert from points to Pertronix, then power the distributor separate from the coil.
The distributor module will want the full 12 V, while your coil wants to see the 8 or 9 V that the resistor wire provides.

Paul - So wire the Petronix off a 12v ignition wire. I'll check out some writeups. Negative wire from Petronix still to coil negative terminal. I am using this wiring diagram, I can't find a full for the 1970 mid years.

 

[EPB72]

yeah negative goes to distributor , power from ignition switch through resistor wire goes to positive terminal on coil,, possible backwards will have erratic misfires under light to medium load or die out all together ,,, a cracked coil arching to whatever would most likely be like engine shutting off as a pose to maybe a single cylinder misfire

 

[EPB72]

Ok, something very obvious I noticed; looks like my mechanic attached the yellow connector (from the dizzy) to the positive, and the resistor wire to the negative. I believe this is incorrect and should be reversed. I assume this would cause back firing but would it even run?? Or am I missing something here.


Thank you, wow obviously printed right there


Paul - So wire the Petronix off a 12v ignition wire. I'll check out some writeups. Negative wire from Petronix still to coil negative terminal. I am using this wiring diagram, I can't find a full for the 1970 mid years.

View attachment 952009

You can splice in before the resistor wire near ignition switch to supply the Petronius with ignition in crank and run positions

 

[tonytony9]

You can splice in before the resistor wire near ignition switch to supply the Petronius with ignition in crank and run positions

Do you know where about the resistor is located? I see the Red w/ Green stripe coming out of the firewall, then runs into a Red connector.

In this use case, the spliced wire (what gauge?) would run to the positive (red) wire on the Pertronix. The black cable from the Pertronix would run to the negative on the Coil? Keep the existing resistor cable red w/ green on the positive.

What does the timing or dwell setting process look like after I install the Pertronix?

I took a look at my points, tried to bump it about onto a lobe in autozone parking lot. They are barely, if any bit open. I definitely could not fit .021 feeler gauge between them. The post on the points looks pretty warn down.

 

[Oldtimer]

Do you know where about the resistor is located? I see the Red w/ Green stripe coming out of the firewall, then runs into a Red connector.

There is not a "resistor" proper.
It is the complete Pink wire (circuit Ø16) that runs from the ignition switch to the bulkhead connector, behind the fuse block.
It becomes the Red w/ Green stripe wire on the engine side of the same bulkhead connector, at firewall.

 

[DirtDonk]

Practically every Bronco dash I’ve ever been under, has had a different resistor wire out of the ignition switch.
Sometimes the wire is red with green for a few inches, then there is a connector that connects to the resistor wire.
Others have the pink/brown wire right up to the ignition switch and no connector.
Still others have red with green for a few inches and then it literally turns to the different pink/brown color. Again, no connector.
Best to just assume that the whole circuit is resistor wire and you’re not supposed to cut and splice into it anyway.
You can splice into the adjacent green with red wire, however, with less hassle.
That comes off the same terminal of the ignition switch as the red with green, but is not a resistor wire. It’s used to power the original voltage regulator.

 

[tonytony9]

Practically every Bronco dash I’ve ever been under, has had a different resistor wire out of the ignition switch.
Sometimes the wire is red with green for a few inches, then there is a connector that connects to the resistor wire.
Others have the pink/brown wire right up to the ignition switch and no connector.
Still others have red with green for a few inches and then it literally turns to the different pink/brown color. Again, no connector.
Best to just assume that the whole circuit is resistor wire and you’re not supposed to cut and splice into it anyway.
You can splice into the adjacent green with red wire, however, with less hassle.
That comes off the same terminal of the ignition switch as the red with green, but is not a resistor wire. It’s used to power the original voltage regulator.

There is not a "resistor" proper.
It is the complete Pink wire (circuit Ø16) that runs from the ignition switch to the bulkhead connector, behind the fuse block.
It becomes the Red w/ Green stripe wire on the engine side of the same bulkhead connector, at firewall.

View attachment 952022

Oldtimer & Paul, thank you for your input.

I will take a picture of my wiring harness tomorrow and send it over to try and identify that green w/ red wire.

Before buying the Pertronix, I bought new points & a condenser (imo good to keep handy anyway in the eb). I am going to replace my existing, I think the post is a bit worn. Been about a year since I last changed them and admittedly I havent done any "upkeep."

I am a complete newbie to points/condenser, this will be my second time. What grease should I use on the Dizzy cam?

If I change the points and condenser, gap them to .021. Do I have to adjust me timing? Unfortunately I do not have a timing light handy at this location, so I will have to do this backyard style. Can you give me some steps to make sure I am installing these correctly with limited knowledge and tools available. Thank you!!

 

[DirtDonk]

If you change and/or adjust points, you will absolutely (most likely maybe) have to change timing.
Simply adjusting the gap on an existing set of points changes timing.
Adding new changes timing 99% of the time.
The only time it doesn’t, is if you randomly get lucky and happened to put it all back together, exactly the way it wants to be.
So hone your backyard timing skills. Not the worst thing to do.
Although a timing light is very handy!

 

[DirtDonk]

Before buying the Pertronix, I bought new points & a condenser (imo good to keep handy anyway in the eb).

Before you get your new distributor, test out the spare points and condenser in the existing one just to make sure they work.
The state of today’s parts, especially condensers, is such a crapshoot that half the time they don’t even work right out of the box.
So best to check.

I am going to replace my existing, I think the post is a bit worn. Been about a year since I last changed them and admittedly I havent done any "upkeep."

And they do need upkeep. Sometimes it seems they need tweaking practically every other week.

I am a complete newbie to points/condenser, this will be my second time. What grease should I use on the Dizzy cam?

Great question. I don’t remember what the experts recommend, but I remember using whatever we happened to have on hand.
Sometimes white lithium, sometimes wheel bearing, sometimes chassis grease. Never had a problem with any, but the rubbing block on some points might not take kindly to some lubricants.

 

[tonytony9]

Before you get your new distributor, test out the spare points and condenser in the existing one just to make sure they work.
The state of today’s parts, especially condensers, is such a crapshoot that half the time they don’t even work right out of the box.
So best to check.

And they do need upkeep. Sometimes it seems they need tweaking practically every other week.

Great question. I don’t remember what the experts recommend, but I remember using whatever we happened to have on hand.
Sometimes white lithium, sometimes wheel bearing, sometimes chassis grease. Never had a problem with any, but the rubbing block on some points might not take kindly to some lubricants.

Got it, I will look for some white lithium or a dielectric grease.

I took a look at my dizzy cap and rotor today. See below pictures.

1. No condensation build up on the cap.
2. I don't see any marks on the cap or rotor.

However,

3. Terminal/contact points on cap seem to have some black build up on them.
4. Rotor front point has almost a rust or build up of some kind on it.
5. I was under the assumption that the center terminal point on the cap should move like a button. Mine seems fixed.

*circled are the terminals with the black build up.
**circled is the center terminal which I was under the impression should not be fixed when you push down on it.

*circled you can see the rust/build up of some sort on the rotor.


Might also be time to replace both

 

[tonytony9]

If you change and/or adjust points, you will absolutely (most likely maybe) have to change timing.
Simply adjusting the gap on an existing set of points changes timing.
Adding new changes timing 99% of the time.
The only time it doesn’t, is if you randomly get lucky and happened to put it all back together, exactly the way it wants to be.
So hone your backyard timing skills. Not the worst thing to do.
Although a timing light is very handy!

I am a huge newbie when it comes to timing. Do you have any resources or step by step guides to checking/adjusting base (initial) and total timing (at RPM). In addition, I have a vacuum advance canister attached to my dizzy. It has two vacuum lines running to it. I believe you have to disconnect one of them when checking timing?

 

[DirtDonk]

Some rotor buttons in the cap do move as if either flexible or spring loaded. But yours doesn’t need to because the tab on the back of the rotor itself is very flexible and can compensate.

The buildup on the tip of the rotor is very common on vehicles that don’t get driven a lot. But also, on rotors that have lots of miles on them too!
Easy to clean up with a little sandpaper or scotch bright in a quick buff.
The contacts in the cap aren’t quite as easy to clean, and we used to use a knife blade in a pinch. But they make little tiny files for that as well.
But at some point, a new cap is the better way to go.

 

[DirtDonk]

Got it, I will look for some white lithium or a dielectric grease.

Wait for others to chime in.
Or just read the service manual that you should probably have!
I didn’t have FORD factory manuals for a long time, and relied solely on the Haynes and Chiltons books. They were extremely helpful through many years of service.
The factory manuals are usually best, of course, but the aftermarket ones aren’t half bad.
Or at least the oldest ones that used to be.

 

[tonytony9]

Wait for others to chime in.
Or just read the service manual that you should probably have!
I didn’t have FORD factory manuals for a long time, and relied solely on the Haynes and Chiltons books. They were extremely helpful through many years of service.
The factory manuals are usually best, of course, but the aftermarket ones aren’t half bad.
Or at least the oldest ones that used to be.

Hi Paul - I changed the points, gap them, changed the rotor and cap. Still have the bucking issue through the mph and rpm band. Any suggestions? Do it be a weak timing chain? Maybe a worn distributor? I am still running dual port vacuum advance canister. I am pretty stumped.

 

[EPB72]

something to recheck is all the secondary wires at cap and plug ends ,,,at the cap are the terminals on the wire seated in the cap with solid metal to metal contact , the terminal can get pushed up if your just shoving the the boot on and not paying attention,, same with the plug end sometimes the terminal will will just slide up inside the boot as your pushing on to plug ...sould lead to misfires under load so good to recheck,,,,,, also checking spark output is a good first step in diag,,, the thexton 404 adjustable spark tester works good and and the markings are pretty accurate ,,,,, also the ground strap/wire in distributor from the breaker plate could cause a cut out seen it when vaccum advance moves wire flexes and depending on sevarity could be momenarly or or full on cut out ,,{broken wires inside insulation } rare but could happen .....