Testing my Coil & Strength of Spark

[SpyderJoe]

Hi guys,
Still trying to sort my "putt putt" issue when accelerating. Before I pull the twin webers and clean them I wanted to make sure my ignition system is sorted. I changed plugs, wires, distributor cap, ignition rotor with no improvement. Compression tests on each cylinder ranged from ~103 - 119. I purchased a Thexton adjustable ignition spark tester #404 to determine how strong my spark is. I set the gap at 28 and couldn't see a spark. Then 20, 15 and finally "SE" - Small engine and still couldn't see a spark jumping. I could hear the tap tap tap but couldn't see a spark. I did get lit up once when I made sure the tester was grounded while I was adjusting it..... Could the spark be so weak to each cylinder that the car will run but not run properly?

I then pulled the coil and tested it with my ohm-meter using IAP video online as a guide. The results were:
neg Post to + post: 1.1
neg Post to Center: 10,500, (same for + post to Center).

If these are normal numbers then I will go ahead and pull the carbs and clean them. I am sure they need them anyway since it has been 4 years since I did so.

[18Fiatsandcounting]

My experience has been that ignition coils either work fine or don't work at all. Not much in between, although I suppose you could get some electrical shorting in between the internal windings that would result in a weak spark. The way I check for sparks is to remove all four spark plug wires (so the engine won't start) and then expose each metal plug connector in turn and place it close to (but not touching) the cam covers. When you crank the engine, you should see and hear a big fat spark. Do all 4 plug wires. You may need to be in a dimly light garage or outside when it's getting dark to see the spark.

If some plug wires appear fine while others don't, the problem is likely bad plug wires or their end connectors.

-Bryan

[spider2081]

place it close to (but not touching) the cam covers.

Cam covers on Spiders are not always an electrical ground. This is especially true on Fuel Injected cars. The covers are separated from the cam box be a gasket and also the retaining fasteners have a fiber gasket on them.
I think its better to use the hood latch behind the engine to check for spark. Put a spark plug in the wire and place the metal portion of the plug on the hood latch.

[18Fiatsandcounting]

Cam covers on Spiders are not always an electrical ground.

Good point, Spider2081, thanks for keeping me honest!!

-Bryan

[DieselSpider]

You would not be putt putting if you had no spark at all however how is your timing and advance working? I'm presuming you set the ignition timing using a timing light after changing out the cap, etc. If its erratic you'd have to revisit the distributor cap, rotor, points and possibly bearings in the distributor or even the drive gear. Were there any signs that the rotor was hitting the towers inside the distributor cap?

You also would not likely hear a weak spark.

BTW: I used to spend a lot of time in Auburn during my youth helping on a farm on Hook Road.

[bobplyler]

In my younger years, I found that having a little brother hold on to the spark plug wire was a good test.

[DieselSpider]

In my younger years, I found that having a little brother hold on to the spark plug wire was a good test.

Hopefully he never figures out what causes that twitch he still randomly experiences.

[18Fiatsandcounting]

In my younger years, I found that having a little brother hold on to the spark plug wire was a good test.

Hopefully he never figures out what causes that twitch he still randomly experiences.

You laugh, but when I first started playing around with engines in my early teens, my buddy and I thought it was cool to hold the spark plug connector on an old lawnmower while the other pulled the starter cord. I really don't understand how I ever survived into my 20s, given the crazy stuff we used to do....

-Bryan

[DieselSpider]

In my younger years, I found that having a little brother hold on to the spark plug wire was a good test.

Hopefully he never figures out what causes that twitch he still randomly experiences.

You laugh, but when I first started playing around with engines in my early teens, my buddy and I thought it was cool to hold the spark plug connector on an old lawnmower while the other pulled the starter cord. I really don't understand how I ever survived into my 20s, given the crazy stuff we used to do....

-Bryan

Yep - Even more amazing that some companies like GM actually used the same frequency for some of their early electronic ignition systems as the pulse frequency of the human heart which greatly increased your chance of not surviving.