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Old 11-13-2012, 05:50 PM   #4
Wrench Rider
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Joined: May 2006
Location: East Virginia
Oddometer: 984
Resistance can be in plug wires (carbon thread core), plug caps, and/or
the spark plugs themselves.

The primary purpose is reduction of stray electromagnetic interference;
mostly with radio-type communications... But, those stray currents can
cause backlash problems for on-board systems; CDI units, computers and
the like.

With the simple Kettering system (battery/points/coil) no resistance is needed
except for radio interference. Not so with modern no points, high output systems.

Also, resistance in plug wires depends on length and resistance per foot; change length,
change wire type, change resistance.

So, changing the original amount of ignition system resistance can cause
running problems.
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