Condenser failure

[SteveJ]

2 hours ago, Yarb said:

IMHO time to pull out the multimeter

Maybe an oscilloscope even.

 

1 hour ago, bluez said:

Have already had test light and meter out checking continuity, voltage and resistance. Not seeing anything amiss, am missing something. 
Great idea hot wire, hadn’t thought of that.

I can detail some testing, but you'll need someone to turn the key while you measure.

[bluez]

Well I used to use tektronix many years ago, no longer available.

[SteveJ]

22 minutes ago, bluez said:

Well I used to use tektronix many years ago, no longer available.

Scopes have become very affordable. https://www.amazon.com/CASE】3in1-Oscilloscope-Multimeter-Generator-Automotive/dp/B0D3LMPQY3

You would also need an attenuator: https://www.amazon.com/gp/product/B07PHMLPV7

And it would be good to have an inductive lead so you can use the spark at a trigger (once you do get spark again). https://www.amazon.com/gp/product/B07CYS9F3L

[Yarb]

@SteveJ Maybe stepping out a bit but could this possibly be a dirty ground issue somewhere in the circuit? 

[SteveJ]

6 hours ago, Yarb said:

@SteveJ Maybe stepping out a bit but could this possibly be a dirty ground issue somewhere in the circuit? 

I haven't seen anything in this thread that eliminates anything since it's mostly been shotgun diagnostics.

[Zpenman]

Have you tried a new condenser? Just removing it from the circuit won't do it, you may get a weak spark without it, but it won't be enough for ignition. The condenser isn't there just to protect the points but to also provide a strong spark.

[bluez]

I’m kind leaning to a short somewhere.

Yes, initially took a bit of shotgun approach. However, I pretty much have ruled out the following: coil, ballast resistor, condenser, and coil wire. All were swapped out with no noticeable change. Have tested some wiring for continuity/voltage with nothing found.

When I first got the car 3 years ago, it had a similar problem with stalling, at that time I found wires to the resistor and distributor were loose, and other minor issues as the car hadn’t been run much in nearly 30 years.

Hope to spend some time on it tomorrow, tempted to try PEI, but don’t think it will make any difference. Will focus on underdash, can’t wait to be a contortionist.

[Zed Head]

On 10/26/2024 at 4:26 PM, bluez said:

Great idea hot wire, hadn’t thought of that.

7 minutes ago, bluez said:

tempted to try PEI, but don’t think it will make any difference.

Seems like you might be overwhelmed with ideas.  Pumping my own suggestion here, but a simple length of wire will allow you to split the whole system in half.  Seems like the cheapest easiest quick and dirty diagnostic.  No oscilloscopes nevessary.  No offense intended to the scope suggesters.  But it seems early for that level of tool.

If it doesn't start, focus on everything after the coil positive post.  If it does start focus on everything before.

Don't forget that you'll have to remove the wire to kill the engine.

[bluez]

Update.. Have spent a few more hrs troubleshooting, with what I guess is some success.  
(Have forgotten how much I hate laying upside down trying to access wires under the dash, where there’s no room.)

Traced and tested wires from distributor and resistor end to end, all good. Disconnected wiring harness plugs on passenger side, all tested good.
Also tried hot wiring, no luck, still not seeing spark at the plug.

Tomorrow will try jumping the tach wires (black/white, green/white). Since everything under the hood seems good, am starting to think the tach is the root of my problem.

[Zed Head]

1 hour ago, bluez said:

Also tried hot wiring, no luck, still not seeing spark at the plug.

If there's no spark with power directly to the coil then working on the wires under the dash won't help.

Study the diagram and you should see.  Did you test for spark from the coil's main output wire?  The center wire?

[bluez]

Thanks for the pic, much cleaner than the one I’ve been referring to.
I get initial spark out of coil wire then nothing, same as before, so my thought is a short. Still have good spark to points.  
The tach and ignition switch are the 2 things I haven’t checked yet. 

[Zed Head]

Sounds like the distributor shaft is not turning.  Take the distributor cap off and watch the rotor when you crank the engine.  Maybe the drive gear has slipped.  It happens, apparently.