I will insert a screenshot of the article written about the two power relays, the step that confused me. In the article regarding the Pertronix power relay, it says to connect the purple wire to the I terminal of the starter relay. We know that is NOT battery voltage in “run”.
Both schematics I have seen for each power relay get battery voltage from the BATT side of the power relay. Makes sense.
Then the only real difference is to where the relay connects - coil, igniter, or electric choke. Here is the screenshot that confused me
The purple wire on the Pertronix relay only closes and holds the relay closed. It goes on the I post and closes the relay during start and run.
I covered how this relay gets closed and held by the I post in my last posting.
A basic relay is a just an electric switch. It has an activation post, a power in post, a power out post and a ground post.
When power is applied to the activation post it goes through an electromagnet to the ground post.
The electromagnet closes a set of points that connects the power in post to the power out post.
In this case the relay is a ‘normally open’ switch meaning that when no power is applied to the activation post (purple wire), no power will be sent to the power out post (the Ignitor).
OK - I have to admit, I didn’t read all 13 pages (6-7), so my answers may be here.
My car will crank, and want to start, but once I let go of the key, it dies.
The coil has good spark when cranking, and I have fuel.
Two questions: Where is the pink resistor wire on a 70? I don’t see it coming out of the steering column under the dash. I’m not a contortionist, so I may just have to pull the seat out to get a good look under there. I thought I remembered seeing the wire “high” up under the dash when I had the dash pad off in my '69… Also, with the key “on” - I should have voltage at the coil correct? (the “resisted” voltage - 6-9v?). I have nothing.
Sounds like you are getting battery voltage to start the car, but nothing in run/on. Yes, there should be resisted voltage there.
It appears from some of the schematics, the actual location of the pink resistor wire depends on if you have a stock tach. I do not have a stock tach. There is a pink wire off the ignition switch on my column, but I’m not sure that is it.
Cruise through all 13 pages. There are some schematics and a really good discussion about all of this. It is odd you get zero volts at the coil after start. I’m sure one of these guys can figure it out.
No tach then I would say either the ignition switch on the column or the resistor wire has gone bad.
Your circuit goes ignition switch to coil + with the resistor wire in between. The ‘pink’ resistor wire is NOT part of the ignition switch pigtail, it is wrapped up in the main wiring harness under the dash.
I would use a volt meter from either end to see if there is 12V anywhere in the circuit when the key is on.
Non-tach cars has the resistor wire from the fuse box (input side…the line is not fused) through the harness, out the firewall plug, to the 3 pin flat engine gauge feed connector. This is for a 1970.
A factory tach was a part of the Eliminator package so unless you have a different car from the one in your signature then your car should have an in dash tach. It is right beside the speedometer. The problem you describe sounds like a tach goes bad as posted above.
Easy to check. Turn the key on and see if you have voltage at the coil. If not then I suspect the ignition switch itself. I have seen both cases.
A car that will not start when in the “start” position with the key, but as you release the key sometimes it will start based on the engine still spinning a bit. No power to the coil in the “start” position.
A car that will start in the start position, but as you release the key to the “run” position it dies. No power in the “run” position.
You can test both cases by removing the large wire to the starter on the solenoid. Have your lovely wife hold the key in the start position and measure the power on the positive side of the coil. My guess is you will have power and then when your lovely wife releases the key to the run position it will disappear.
Wow - do I feel dumb !! Yeah - it does have a tach. I guess I should try to come up with an excuse for that.
The puzzling thing is that literally, the last time I hit the key, it started and ran fine (months ago).
Yeah, your pic was the reason I went with the open tach. Unfortunately that is how the factory tachs fail - the engine shuts off.
Follow the tach wires about 6" and you will come to a flat connector.
Disconnect the tach from there and install a jumper wire on the engine side if that connector.
That will by-pass the tach and complete the circuit to the coil. If the car starts the tach is the problem.
Does this method above just diagnose the ignition switch? I definitely have voltage at the coil when I crank it. I do not have voltage at the coil with the key “on”. It will “start” when I crank it and die as soon as I release the key.
You might have a bad tach or a bad ignition switch or a bad starter solenoid or a wiring problem with those symptoms. This is why using a multi meter saves time and money.
Thanks, all for your feedback. Royce, i have a meter, but I’m just not well versed in using it, ie: what to test, where - esp if we’re talking ohms.
My father was an electronics technician. I should have spent some time with him learning all about that when I was younger. I guess today, i need to watch a youtube video!
I guess I’ll be pulling the dash pad to jumper the tach and do some other diagnoses.
Here’s a question - can I run a jumper (temporarily) from the battery to the coil - with an inline resistor just to hear it run a little bit?
I just finished putting exhaust on the car and want to hear it
Run a jumper from the battery to the positive side of the coil. You do not need a resistor for a test run. Lack of a resistor will just wear out the points a pit faster. I agree that it sounds like a tach problem. You will need to remove the jumper to stop the engine. Just pull it off and the engine will stop. If not then the tach magically fixed itself!! Doubt that will happen.
I’ve read through all the posts as I’ve had a similar problem as Rick. Bob Rocketman has been a great help via email.
What I need to confirm is the wire locations at the regulator. My harness is missing the black plastic piece that keeps the wires in place.
Bob says
Orange wire in F
Yellow in A
S terminal is open
Green/red in I
I’m going to take this as correct. My issue is that the diagram shows no letters. It does show that the open terminal as being one of the ends.
My original problem was a bad solenoid draining the battery. While diagnosing that I pulled the wires off the regulator (and of course didn’t take a picture). Now the violet resistance wire is overheating and smoking when the key is in the run position.
Also screwing me up is that I have a MSD distributor, 6AL and tach adapter.
