no spark

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fcgadget

fcgadget

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Dizzy died, threw a nut.
Replaced it. No start
Replaced the coil, no start
Coils were both - to + 3+ ohms, + to center 8K ohms
Battery at 12.5 volts
Voltage at starter 8 volts
Voltage at coil (bypass) 11.5 volts
coil to dizzy wire ~4k ohms
NO SPARK from coil center to ground
tested for spark without that wire, just a heavy gauge wire NO SPARK

I know that "new" stuff doesn't always work...
Can anyone suggest something before I buy another coil??
 
Put a jumper from the +pos of the battery to the coil - aka hot wiring, bypass your switch and stuff. Does it have points? Run a points file threw them to clean off the protective coating - if points don't conduct current no sparkie. I don't do inductive spark/brain boxes for a reason.
 
I seem to recall, the coil requires the (-) terminal pulled to ground to produce spark, which is the function of points or igniter/pickup.

You might go through the FSM to verify that test and retry your spark test while manually inducing a spark by pulling the (-) terminal to ground, briefly.
 
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The hot wire goes from the pos battery to the pos coil. The neg coil goes to the points. When points open is when the coil produces spark. Its the collapsing field of electricity flowing threw the coil.
 
fcgadget said:
ran a wire direct to the coil + from the battery
while cranking, briefly touched the coil - to ground
no spark
Click to expand...
Unless I'm missing something, it seems like you've eliminated quite a few upstream and downstream components with that test, (ignition ON, but cranking not necessary in your test above).

So, full 12v directly from the battery (+) to coil (+) (bypassing the ignition switch), lead from coil center directly to a working spark plug touching ground (bypassing distributor), briefly touching coil (-) to ground (to simulate points), and no spark?

It would seem that would leave you with only a few possible remaining issues keeping you from getting spark:
- bad coil (unlikely based on your continuity test)
- bad coil wire connection or spark plug
- bad ground somewhere (seems very possible).

About the possible ground issue, you may want to check continuity from the battery ground, to the ground you used to touch coil (-) to. To verify a ground issue, you could re-run the test, using battery ground to touch coil (-). If you get a spark then, you probably have a ground issue.
 
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CruiserInProgress said:
Unless I'm missing something, it seems like you've eliminated quite a few upstream and downstream components with that test, (ignition ON, but cranking not necessary in your test above).

So, full 12v directly from the battery (+) to coil (+) (bypassing the ignition switch), lead from coil center directly to a working spark plug touching ground (bypassing distributor), briefly touching coil (-) to ground (to simulate points), and no spark?

It would seem that would leave you with only a few possible remaining issues keeping you from getting spark:
- bad coil (unlikely based on your continuity test)
- bad coil wire connection or spark plug
- bad ground somewhere (seems very possible).

About the possible ground issue, you may want to check continuity from the battery ground, to the ground you used to touch coil (-) to. To verify a ground issue, you could re-run the test, using battery ground to touch coil (-). If you get a spark then, you probably have a ground issue.
Click to expand...
connections were direct to battery +and -. just held a large wire from a clip in the coil center to near the battery - and watched for a spark there. I wasn't sure that the coil to dizzy wire was good, though it did measure at 4K ohms (~12")
3_puppies said:
is the distributor seated and rotating?
Click to expand...
seated and rotating but not connected to the coil. tried to keep it simply the coil test
 
Very curious.

If you are in doubt about the distributor lead, you can use any other lead (or just a wire) to swap out for the test. Same goes for the coil. Do you have another, known good coil around to make sure your test is valid?

Stepping back a bit, are you running straight points or electronic ignition (with igniter hanging off those coil terminals)? If you have anything else (points or igniter) connected to those terminals during your test, you may want to disconnect it to make sure you aren't inadvertently grounding that coil (-) continuously.

Having done all that, and still not getting any spark from the coil, without anything else connected to it, either the coil is bad, or in someway the test isn't working.

I did a search for that type of powered coil test and found this helpful article.

classicmotorsports.com

9 steps to easily diagnose ignition problems

As it turns out, most common ignition problems are actually easy to diagnose.
classicmotorsports.com classicmotorsports.com

They make use of a test light, So I hope I'm not suggesting something that won't work for you.

I did a similar test on my 79 coil/igniter combo that came out of the FSM and produced a very visible spark without any spark plug. But, I didn't need to strip the test back to coil only like you're attempting. Seems like it should work.

Curious what you find.
 
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distributor mechanically failed.
replaced it. no spark.
checked battery. no spark
replaced coil. no spark
checked voltage at coil +, coil -. no spark
checked voltage drop at coil. no spark
replaced new dizzy. no spark
measured all plug wires, looked to be within specs
traced all wires involved. no problems

Finally replaced the coil to dizzy wire. it worked!!!!!!!

apparently it was an intermittent connection with that wire
 
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