Coil bad?

V

vern hodgson

Well-known member
I have spark at the points but no spark plug spark, using a test lite batt, side of coil lite shines bright, on other side of coil lite is quite dim. Is coil bad and why no spark at plug?
 
When you "pop" the points you should get a nice hot blue spark out of the coil. Open the distributor and use a hand crank to turn over the engine until the points are NOT on a lobe (closed), turn on the ignition, use a wooden popsicle stick or a screwdriver if you are careful and snap the points open/closed. If the points are closed, one side of coil should be battery, other side ground. Clean points.
 
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You should have the same voltage at either low tension post of the coil. Your test with the light is telling. I suspect that the primary winding is grounding out inside the coil. Check if you get a reading with your test light from one post of the coil to the metal case, which would show that a short has occurred.
 
Like Eagle said snap the points while holding the end of the coil wire a short distance away from a head nut to check for a nice blue spark. If you have a good spark there then check the condition of the caps graphite button contact to see if it is worn down. Then check the condition of the rotor.
I just had the same trouble today with a club members Roadster. The rivet holding the spring steel that contacts the button on the cap to the fixed contact on the rotor was loose. Replaced the rotor and all is now good.
 
1crosscut said:
Like Eagle said snap the points while holding the end of the coil wire a short distance away from a head nut to check for a nice blue spark. If you have a good spark there then check the condition of the caps graphite button contact to see if it is worn down. Then check the condition of the rotor.
I just had the same trouble today with a club members Roadster. The rivet holding the spring steel that contacts the button on the cap to the fixed contact on the rotor was loose. Replaced the rotor and all is now good.
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Ok, on the agenda for tomorrow, may have found the problem, I will organize the wiring so it is not a jumbled rats nest but I had coil wire going thru a 90degree boot and that may have prevented the coil wire from going in far enough to make contact.
 
I know what it is now! your pet rats nest. Good Luck Vern!
 

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Clean the coil wire socket, and the wire ends! I had a boot on the wire that goes into the coil, out of sight out of mind.
 
Are you sure that it's a 6V coil? Not 12V? Primary side resistance should be~1.5 ohms.
 
Do not replace anything until you have verified its fault. What is the voltage on each side of the coil when the points are closed? Should be battery on one side, very near ground on the other. I think you'll find its not being grounded properly through the point/switch circuit. Clean and set point clearance.
 
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