Stalling, intermittent no spark

So my 1970 stalls every now and then, finally it just stalled and wouldn’t restart. I have spark at the ignition coil wire going into the cap, but no spark at plugs
Do these have pick up coil?
I replaced the ignition coil and new condenser
Any ideas?
Alex

Did you replace the cap and rotor ?

I’ve had the center pickup on the rotor break before and would give the symptoms you’re describing.
What about the points ?
Check the gap at the plugs ?
How old are the wires ?

Did cap/ rotor/ wires/ plugs/points/last year

I checked the cap and rotor, both look like new, no odd carbon marks
Very odd that it can drive miles without issue, then it start to stall, most times it restarts, not now

If you have spark at the coil, then it is either the wire to the cap, the cap, or the rotor.

Yes. I have spark coming out of coil wire, none at end of spark plug wire

Why would it run fine for miles, then start to stall( like running out of gas)

Every time that has happened to me it has been a bad tachometer. Unfortunately your signature doesn’t say whether you have an XR-7 or not so I am only guessing that you have a factory tach.

Hi,
No tach, have clock

I replaced th he cap. Rotor, condenser, coil
I have spark coming from coil wire to cap
No spark at plugs. Wth???
How can this be??

The worst case scenario is that the rotor is not turning. That is usually caused by broken timing chain. Have you verified that the rotor is turning?

I had an uncle that was an MIT PHD graduate in electrical engineering. He designed the Washington Moscow Hotline following the Cuban Missile Crisis. Before that he was a “nuclear payload delivery engineer” AKA a real honest to goodness rocket scientist. Very smart guy. He drove from Washington DC to Oklahoma City in a brand new '68 Fairlane that was only running on three cylinders. It wouldn’t go faster than 50MPH. He spent about an hour explaining to my dad, an ex Ford trained mechanic how it was theoretically impossible for the spark plugs to be all bad simultaneously. He had calculated the statistical probability to a half dozen decimal places. Impossible. While he was pontificating, my dad put three new plugs in it and it ran like a top. Some times what you see is more important than what you think. Replace the rotor and then the cap.

I replaced both this morning

How are you determining there is no spark at the plugs ?

There are a number of ways to do it with various degrees of effectiveness …

If you’ve got a timing light you can hook it to the wire and you should see spark there if there is current.
You could pull a plug clear out and put it against the block so it has a ground path (just sitting in the open it may not make contact enough for a circuit – be very careful holding it, that’s a lot of volts so it’ll wake you up if it hits you instead of the ground.
There are test tools as well that you plug the wire into and clip on a ground, then you can adjust the gap and see how much fire it gets.

And as others have said, are you sure the distributor is spinning when the engine turns over ?

It is now extremely easy to troubleshoot because it is no longer intermittent. Get the first question out of the way - is the distributor turning? If so then you need a volt meter set to the 25 volt DC scale, if it is not self ranging. Do not buy any more pars until you are certain of the reason voltage is not present at the plugs.

1: Make sure that there is Power (+) and ground (-) at the coil. It needs to be there while cranking (key turned to “START” position) and while the key is in the “RUN” or on position.

Do that and I bet you figure out that one or the other is not there. Don’t buy or replace anything until you know where the problem is.

OK Royce, thank you and I will report back Wednesday

I’ve had a similar issue with a different car, could not wrap my head around it, exact same symptoms as you describe. Spark to coil, spark to points, but no spark at the plugs. After buying everything new (was all over 20Years old btw, so couldn’t hurt) still same issue.
Since I’ve tried starting the car a few times, I put the battery on a charger, and guess what. Started right up with no issues, So got the battery checked out and it did put out enough juice idle, but under load it dropped bad. Replaced the battery and no troubles since :slight_smile:
So maybe you could check the battery out at a shop?

New battery didnt help
Have weak spark at the end of the coil wire,with either new or old coil. Seem to want start if i grounded the coil?

This is the first time we have heard that you have a weak spark. It should be blue white and make a sharp tick when sparks. If it yellow or won’t jump much of a gap that means that the coil is not creating much voltage. First off, run a jumper wire to the coil positive from the battery positive post and see what happens. If it starts and runs you may have a bad resistance wire. If it is still weak, I would take the condensor wire of the points and see what you get. It is a slim chance but while you are there, confirm that the little braided wire is still connecting the breaker plate to the distributor housing. Check the points gap too. If it has closed or the contacts are burned that can be your problem. When all else fails prove out that everything works. You can check the coil by removing the ground wire that runs to the distributor and using a test lead to ground the coil. When you lift the lead you should get a good solid spark from the coil wire to ground.

We did jump the positive post on the coil, no change

Good. Now check to be sure the points are not burned and the gap is set correctly. Check the spark. If it is still weak then remove the condensor wire from the points.

Will pick up points tomorrow. Set them at .021 correct?