Do I need a new coil or is it much more than that?
I'm always dealing with lots of changes under the hood by the PO but the one giving me fits right now is the ignition system. The Jeep has run adequately in the past with it's current set up but that's no longer the case. The engine will crank just fine but won't start. I've had the carb (Carter AFB) rebuilt and everything there seems fine. I'm even using fresh fuel. Checked for spark on the plugs and got nothing. The wire from the coil to the center of the distributor will spark once when I initially turn the key but then nothing. Most of the advice online is geared to the standard set up. I have the original 258 six in my 81 CJ-7 but here's where I need some help. I've got a Mallory distributor (model 2360101) that I assume isn't original. The Mallory coil doesn't look original either. The ECU is still mounted to the driver's side fender but has been disconnected. I'm not necessarily looking to go back to the factory set up but I'm not sure where to go now. I found some diagnosis procedure online and here's what I found: with the ignition in run, voltage out of the positive coil terminal is 12v., with the 'I' terminal on the starter solenoid disconnected I still get 12v from the coil. If I connect a jumper from the negative terminal on the coil to ground then I get 6v out of the positive terminal. The instructions from there get into checking the connections of the ECU which is no longer connected. I need some advice from you experts that appear to have seen every possible configuration based on the great responses in this forum.
You have the right voltage at the coil. It sparks once because you are energising and de energising the coil with the key, it is normal.
The I terminal gets 12V from the solenoid in Start only, in Run you are just measuring what is in the ignition system at the coil i.e. after the ballast resistor / ballast wire. In a standard CJ this would be 7V but you do not have a ballast, you do not need to connect to the I tab at all.
What you have is a dual point distributor. In other words someone has junked your electronic ignition and taken you back 50 years in technoloy terms to POINTS by installing a Mallory distributor.
The problem is with the switching on and off of the coil by th epoints. You need to take the distributor cap off and see if you can find some points opening and closing as it rotates.
The points allow the primary winding in the coil to energise, which induces a magnetic field in the much more wound secondary coil to build and then, when the points are opened by a cam arrangement, the magnetic field inside the coil collapses and a large voltage (could be 20 kV or greater) is produced in the secondary winding.
The points are just two contacts mounted on a base plate, with on econtact bing oushed up and down by a cam on the distributor. They can melt, close up, move and burn. They are a pain to maintain and you need a dwell meter to set them properly. Setting the static timing is no more complicated than rotating the engine until you hear them open and seeing where the marks on the crank pulley align. You can try to fix the gap when on maximum cam with feeler gauges and this will approximate to the dwell gap.
The dwell gap is for the coil to de energise, to give it enough time. If set incorrectly the spark energy produced will be effected.
The capacitor is attached to the points (that little can on the side of the distributor) and has two functions:
1) it absorbs the back EMF from the magnetic field in the coil to minimize point contact burning and maximize point life; and
2) it forms a resonant circuit with the ignition coil transferring further energy to the secondary side until the energy is exhausted.
Changing the condenser will not fix your issue, which I suspect is points or points gap related. However a failed condenser may have lead to burned points.
This system became the primary ignition system a century ago and for many years it was used due to its low cost, high reliability and relative simplicity. However it is not maintenance free and it is sooooooo much easier to have an electronic pickup.
First thing I would check is the voltage at the coil + when in start to verify if the ballast wire is working or not. It may still be in that Mallory circuit. I know my Accel coil still needs it.
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Why would you spend the money to get a oem distributer (not even knowing if the reason he went that way was that he was having problems). Why not go with something like mallory unilite distributor (3 wires) or a DUI, or something like that. I'm sure the guys on here can recommend a system. Years ago I used the unilite on my cj7 and it ran great. On the cj8.com forum I have the unit for sale since I went with a chevy engine. This is not a ad for it, I would have said everything I said anyways.
Electronic ignition is better than one with points. Just looking at the easiest and most economical.. Certainly there is a veritable plethora of options available as always in the aftermarket venue. I know you points guys are going to say tuned up etc, etc, but for ease of maintenance and performance I would go electronic.
I just checked inside the distributor and things look pretty good. Inside the cap was like new. I've attached some pics showing the overall as well as close up of the points. The gap on the points is only 0.006 which I assume isn't correct. Where would I look to find the proper gap setting for my system? From what I understand, this was a standard set up for early 70s CJs with the 258 six. Should I use that recommended gap setting?
Old school trick here.
Set lobe on dizzy shaft so the points are at their widest opening.
(To do this-Ign OFF-put tranny in highest gear. Push against Jeep to move dizzy shaft to desired point.)
Take a match book cover and set gap to just let the cover slide between the contacts.
That will get you in the ball park.
I still would replace the condenser......
Have'n you along, is like loose'n 2 good men
That match book trick also cleans the crap off the contacts too.
With ignition on after you set the gap with your match book take a sparkplug and jam it into the coil wire where it would plug into the distributor cap and set it on a metal surface.
Turn on ignition and place a small screwdriver blade across the open points gap and wiggle it. You should see spark. Wiggling it will simulate the points opening and closing. Or just stick the blade in the open gap and pull out real quick.