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No Spark from Coil
#1
tach 
I have a 351small block that cranks but doesn't fire. Battery is good. I checked voltage into + coil and it's above 12v with key forward....I checked spark at plug wire ends...no spark at all.... I pulled coil wire at distributor and get no spark when grounded to block.........I did ohm test to coil and it appears ok......voltage off + coil is above 12v..... think it's coil but omh test says otherwise.......overheated engine.. now no spark.
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#2
Cap and rotor condition?

Ignition type?

[Image: 1_01_07_15_8_53_18.png]

"I love my Hookers!" and "Get some Strange" probably have a different connotation to non automotive enthusiasts!
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#3
Jeff73Mach1;187957 Wrote:Cap and rotor condition?

Ignition type?

Old but clean. points couple months old, didn't replace condenser (7 years old). Is there a way to check voltage from coil to distributor?

original points condenser....no upgrades


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#4
make sure trans in Park or Neutral, possible neutral safety switch issue.

i would swap coil and retest for spark. i had a bunch of coils fail in different ways, maybe the secondary step up coil went but the primary is fine.

from there condenser. maybe ohm test the coil to cap ignition wire or swap and see if the wire is the problem.
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#5
hetrickw;187958 Wrote:
Jeff73Mach1;187957 Wrote:Cap and rotor condition?

Ignition type?

Old but clean. points couple months old, didn't replace condenser (7 years old). Is there a way to check voltage from coil to distributor?

original points condenser....no upgrades
will change out coil @ see what she does......thanks for assistance.
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#6
If you have a timing light, it can be used as a spark tester too. Putting the pick up on the coil to distributor wire should have it flashing pretty fast even during cranking.

If you haven't checked the rotor recently, take a look as sometimes strange things happen. Ive seen the "button" on a rotor fall off and have seen caps where contacts did not truly make contact.

[Image: 1_01_07_15_8_53_18.png]

"I love my Hookers!" and "Get some Strange" probably have a different connotation to non automotive enthusiasts!
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#7
With the distributor cap off and the points in the closed position, ignition key on "run" not start,,, Open and close the points with a small plastic or wood blade.. If you see a spark jump between the point surfaces, the problem rests with the coil.. Hope that helps.
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#8
Make sure the points are opening and closing, should have 0.016 inch gap when on the high point of the cam.



“If you can't explain it simply, you don't understand it well enough.”
--Albert Einstein
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#9
Don C;187992 Wrote:Make sure the points are opening and closing, should have 0.016 inch gap when on the high point of the cam.

thanks, all...i'll just replace Cap/coil/points/condenser and see if that gets it. can't be much more since I've got voltage to the coil right?
checked resistance on coil/dist. wire and it looks good.

I always appreciate the great suggestions/knowledge on this site...
Bill
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#10
Check the amperage as well. I had that issue with an old flat head. 6.4 volts (good for that system) at only 0.1 amp will not make a spark. I had enough contact at the wire from the switch to get voltage but not enough for the proper amperage. It took forever to track it all the way back to the loose connection under the dash.

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