When does the plug fire?
 

I should know this but does the plug fire when the points open or close?
Thanks!!

Re: When does the plug fire?
 

"Every time the points open, the flow of current is interrupted through the coil, thereby collapsing the magnetic field and releasing a high voltage surge through the secondary coil windings. This voltage surge goes out the top of the coil and through the high-tension coil wire. Now, we have the voltage necessary to fire the spark plug"

Re: When does the plug fire?
 

Thanks Pete!

Re: When does the plug fire?
 

The plugs fire when the distributor points open and the rotor is pointing to one of the terminals inside the cap. The amount of time required to charge the coils is called the "dwell". When the points open, the collapse of the field in the coil results in a high voltage surge which fires the plug(s). When setting the dwell, the use of a machine will get a maximum result

Re: When does the plug fire?
 

Pete, think of the coil being charged up when the points are closed. When they open the coil releases the built up charge to whichever plug is waiting for it.