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Discussion Starter · #1 ·
Hey y’all. I just recently picked up a 316 with the B43E. It wasn’t running when I got it but I’ve checked most of it over. It’s getting fuel but no spark. Engine turns but I can’t get her to fire. I’ve changed the ignition coil, condenser and points, plugs, battery.
I’ve checked all the safety switches at the shift lever and the seat safety has been bypassed.

Is there a fuse or something that I am missing? I’ve only found one fuse behind the battery.


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Hello murrayford96, welcome to the forum.

For testing purposes, try running a "hot wire" from the battery positive terminal to the coil input terminal. Check spark in a shaded area so you can see the spark.
 

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The points serve as a "switch" to the ground side of the coil (- terminal). Battery voltage into the coil through the + terminal. Voltage builds through the primary coil windings, but it's just going to ground because the points are closed. When the points open, the magnetic field between the two windings collapses, and is multiplied by the secondary windings. That energy will seek the path of least resistance to ground. That now comes through the spark plug wire, by jumping across the spark plug electrode.

Hope I'm not insulting you by given you the "Point Ignitions 101" lecture, but you'd be surprised at the number of people today that are not familiar with how they work. You can get the coil to fire across the spark plug electrode(S) without the engine even running. Simply operate the spring-loaded side of the points arm with the eraser end of a pencil. I learned to use the eraser end of a pencil after being "zapped" several times using a screwdriver. With 12V going into the + terminal of the coil, you are simply operating that switch to ground through the points which is normally activated by the point lobe rotation. The plug should fire... If it doesn't, it's a simple circuit to trouble-shoot if you understand it.

Believe it, or not, with the dual lead coil the B43E runs, both spark plugs fire at the same time. Only one produces power because the piston is at TDC of the compression stroke. The other spark is just "Lost". That's why it's called a "Lost spark ignition". Make sure if you check it with the pencil method that both spark plugs are out. I've said a lot of bad words that my Granny wouldn't have liked because I was only looking at the side that had the bad spark plug/lead
 

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New doesn't mean good I've found out.
Run coil wire to a new spark plug, be sure plug threaded body is grounded.
With a test light or voltmeter I'd see if you have power on +positive coil side, key on. With points closed use something insulated (plastic, etc) to open points. Every time you open points plug should spark. Key off (don't leave on motor not running).
I recently had a motor no spark, the new condenser was bad (open).


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Discussion Starter · #5 ·
The points serve as a "switch" to the ground side of the coil (- terminal). Battery voltage into the coil through the + terminal. Voltage builds through the primary coil windings, but it's just going to ground because the points are closed. When the points open, the magnetic field between the two windings collapses, and is multiplied by the secondary windings. That energy will seek the path of least resistance to ground. That now comes through the spark plug wire, by jumping across the spark plug electrode.

Hope I'm not insulting you by given you the "Point Ignitions 101" lecture, but you'd be surprised at the number of people today that are not familiar with how they work. You can get the coil to fire across the spark plug electrode(S) without the engine even running. Simply operate the spring-loaded side of the points arm with the eraser end of a pencil. I learned to use the eraser end of a pencil after being "zapped" several times using a screwdriver. With 12V going into the + terminal of the coil, you are simply operating that switch to ground through the points which is normally activated by the point lobe rotation. The plug should fire... If it doesn't, it's a simple circuit to trouble-shoot if you understand it.

Believe it, or not, with the dual lead coil the B43E runs, both spark plugs fire at the same time. Only one produces power because the piston is at TDC of the compression stroke. The other spark is just "Lost". That's why it's called a "Lost spark ignition". Make sure if you check it with the pencil method that both spark plugs out. I've said a lot of bad words that my Granny wouldn't have liked because I was only looking at the side that had the bad spark plug/lead
Thank you and no offense taken here! I’m a DIYer but in no way am I a professional. When you stop learning then you stop living.

I’ll run these tests tomorrow and update y’all.


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