Ignition coil testing
Seasoned HDF Member
Joined: Aug 2007
Posts: 8,199
Likes: 3,087
From: NW AR
That's not a HD secondary coil he has (had?) there. On a HD coil, which fires in waste spark, the secondary circuit is: Ground through one spark plug to coil to ground through the other spark plug. The cylinder not on the compression stroke acts as a low resistance and the one on the compression stroke acts as a high resistance.
With a single fire (or dual fire, whatever, not waste spark) coil where it is really 2 coils, like is pictured above, then the secondary circuit is (near as I can tell) the same as on a car: Ground through the coil body to coil to ground through the one spark plug. Unless they are doing something different.
With a single fire (or dual fire, whatever, not waste spark) coil where it is really 2 coils, like is pictured above, then the secondary circuit is (near as I can tell) the same as on a car: Ground through the coil body to coil to ground through the one spark plug. Unless they are doing something different.
Road Warrior
Joined: Oct 2011
Posts: 1,376
Likes: 36
From: Round Rock, TX
That's not a HD secondary coil he has (had?) there. On a HD coil, which fires in waste spark, the secondary circuit is: Ground through one spark plug to coil to ground through the other spark plug. The cylinder not on the compression stroke acts as a low resistance and the one on the compression stroke acts as a high resistance.
With a single fire (or dual fire, whatever, not waste spark) coil where it is really 2 coils, like is pictured above, then the secondary circuit is (near as I can tell) the same as on a car: Ground through the coil body to coil to ground through the one spark plug. Unless they are doing something different.
With a single fire (or dual fire, whatever, not waste spark) coil where it is really 2 coils, like is pictured above, then the secondary circuit is (near as I can tell) the same as on a car: Ground through the coil body to coil to ground through the one spark plug. Unless they are doing something different.
For terminology clarification, the primary coil circuit is what we would normally call the input, and the output.... to the plugs is the secondary.
At least that is my understanding, but I'm certainly open to correction.
Tourer
Joined: Aug 2006
Posts: 282
Likes: 7
From: Southern MD
When most of us refer to ground we mean a piece of metal on the coil that touches the bare chassis. Attached is a single fire coil and there is no chassis ground on it rather the body is all plastic. Current has to flow in one terminal and out another even if it's 1 milliamp at 20000 volts. If we assume current flows out the spark plug wire to make the spark, current must also flow in either the +12 terminal or the grounded minus terminal of the non-firing cylinder. The firing cylinder's minus terminal has just been ungrounded to create the spark so current can't flow through it.
This post was probably a mistake since to most people it will sound like nonsense but at least I included a pretty picture!
D-gyver included the perfect pic for testing a single fire coil though. Thanks for that.
This post was probably a mistake since to most people it will sound like nonsense but at least I included a pretty picture!
D-gyver included the perfect pic for testing a single fire coil though. Thanks for that.
Last edited by Rob85WG; Aug 18, 2015 at 09:18 PM.
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