No spark...
 

Ahoy,
Had a shutdown while underway last weekend. Sailed back to the slip without incident... Anyway, here's what I know.

I had been running the engine for an hour before a two-hour sail. I restarted and the engine ran for 10 seconds before abruptly shutting down. It shut down as though it had been turned off.

Back at the slip... She turns over but still won't start.

Ether in the carb intake did nothing. She didn't even think about starting.

With a circuit tester, I established that spark was getting to the coil with the engine briefly turned to RUN.

Next, I pulled the #1 spark plug wire, attached a plug and held it to the head and cranked the engine. No spark, nothing.

Next, I checked the voltage to the coil with a multimeter, one element to the positive coil, the other to the head while engine on RUN. The voltage fluctuated wildly between 13. 3 - 14.2 volts.

Next, I checked the points: .017" which is a little tight.

While the distributor cap was off, I noticed a tear in the insulation on the black wire where it exits the distributor. Patched with tape, tried to start... nothing.

I checked for spark with a plug in the #1 wire as before, but no spark.

PAY ATTENTION HERE, AS I WANT TO CONFIRM I CARRIED OUT THE TEXT CORRECTLY.

Next, I checked the coil spark. I pulled the big coil wire from the top of distributor. Then I took a foot-long section of wire and attached it to the neg coil post with the other wires removed from the neg post. Then, with the engine on RUN, I intermittently held the neg wire to the head with one hand while holding the thick coil wire a quarter-inch from the head. There's supposed to be a "snappy blue spark." What I saw was a faint spark, maybe once or twice while intermittently touching the head with the neg lead. All I got was what looked to me like a weak-ish spark once or twice, and then no spark at all.

The coil is from MMI and is 6 months old. It replaced one that failed in October. I'm always conscious about immediately turning the key to OFF whenever the engine may hick-up and not immediately start (it has always started on the second go around).

So my thoughts: Electricity is getting to the coil, but not exiting with authority. If the coil has failed, it would be the second coil failure in two months. If it is indeed a coil failure, it would stand to reason that something is causing them to fail.

First, I need to know if I carried out the proper tests and carried them out correctly. Also, I'd like to know what could be causing the coil failure, if it has indeed failed. Could a failed condenser cause a coil to fail? Could the breach in the neg wire insulation from the distributor cause it?

Thanks for you help! Much appreciated!

Sounds like a coil failure to me. Make sure the spot you used to ground the coil is a good clean metal contact, i.e. not through paint.
Question number 1 - what is your system voltage under way?

I'm not sure what the voltage is underway. I'll need to get the engine running before I can find out.

It was a pretty quiet shutdown -- not the "raucous" shutdown some have associated with coil failure shutdowns.

You may have answered your own question:
If this insulation damage resulted in the wire shorting to the distributor body where it exits, it is the same effect of the coil being energized without the engine running and depending on the time, is guaranteed to cook off the coil regardless of its age. My advice is to replace (rather than tape) the damaged wire and also replace the coil.

BTW, your testing protocol sounds spot on to me.

It probably sounds really familiar to you, Neil. My mind has been awakened to the dark art of troubleshooting... at long last...

So a new coil is the next move? Could a failed condenser also cause coil failure? The condenser and points are 8 years old...

I would replace the coil, points, and condenser for sure and maybe the cap and rotor.

I agree with Joe, make it as good as it can be.

Got it. I'll report back. Thanks, gentlemen.

I would do Coil and damaged wire to confirm that is the issue. Then change all the other parts, so no confusion is added. Also would know what to throw away or keep as spares

Also get a good voltmeter ;)

Is my cheap digital multimeter the cause of the wild reading? I've got almost $13 invested in it...

If you don't mind spending a little, I recommend this digital multi-meter from Harbor Freight Tools: https://www.harborfreight.com/600a-t...ter-64015.html It packs a lot of features including automatic range and DC amps via the clamp.

Spark ignition with points/condenser is a weird beast. Primary circuit is pretty straight forward: current in the + side of the coil, out the - side of the coil, to the points, then to ground. The high voltage side is where things get strange. I used to think it was high voltage out the top, to the plugs, then through the head/block to the case of the coil. Not so - there's no continuity between the high voltage connection at the top and the case of the coil. Turns out the other side of the high voltage winding is connected to the - terminal. The return path for the spark energy is through the points/condenser! And since the points are open, the condenser is doing the work.
Why is it this way? I have no idea!
Can a bad condenser kill your spark? You bet!

This is an A4, You can see the spark is more like an RF event than DC and the condenser is definitely required for it to work. The little blip in the middle is the points closing.

stopage while under way
 

I had the same exact scenario last season .. Motoring to the mooring, the engine just stopped ..

Turned out I needed to clean the points . it worked for me ..

just went through this today. If it is a late model A4 your point gap should be closer to .023. I would check this first

Good time to move to EI if you want to, you'll be doing about the same work either way. YMMV on which EI you like.
Here is why we have such a hard time with coils:

Finally reporting back on my "lack o' spark" situation. As you may recall from the above posts, I established normal voltage to the coil, but a very weak spark from the coil and no spark at the plugs. A couple of weeks ago I put in an order with MMI for a new coil, along with a new condenser, points and plugs, as they've all got eight years on them.

Got everything installed, double checked that the points gap was correct, AND REPLACED THE WIRE FROM THE DISTRIBUTOR WITH THE BREACHED INSULATION... feeling confident... and, after sitting in the slip for nearly a month, she started right up... running like a raped ape.

The time I spent troubleshooting and addressing the problem was maybe a couple of hours. To all of you who try the scatter-shot approach and hoping to get lucky with a guess as to the problem -- as I have done in the past -- you need to hear me now. Listen to the folks on the forum when they ask, "Do you KNOW" this or that... And then answer the question.