That's called the "rotor". A "rotary button" is the term often used to describe the heater fan switch, wiper switch, or headlight switch if it's the turn-type of switch. When you talk about the "rotary button" in the distributor, that's the spring-loaded carbon contact in the center of the distributor cap, so you can see why anyone would be confused with your terminology.
You still didn't say what the symptom or problem is. In very rare instances a rotor can become shorted due to a condition called "punch-through". That's a huge problem with the older GM HEI systems that used ignition coils capable of much higher voltages than needed to fire the spark plugs. If you unplugged a spark plug wire while the engine was running, and held it too far away, the spark would find an easier path to ground through the rotor. Once that happens, a carbon track is left behind. That carbon conducts current so from now on spark current will go to ground through the rotor instead of following the more difficult path through the carbon-impregnated string in the spark plug wires. That results in a no-start condition.
On most other ignition systems, yours included, the maximum voltage stock ignition coils can produce isn't usually sufficient to cause punch-through, but if moisture got inside the cap, that can conduct the spark current and cause carbon tracking too. Often you can't see that so it's easier to just replace the cap and rotor. The clue is you'll have good spark at the coil wire but not on the spark plug wires.
You can also have a single-cylinder misfire if there's a carbon track inside the distributor cap near just one terminal. That almost always starts out from moisture. Cleaning the cap is rarely a permanent solution.
There was also a real common problem on Chrysler V-6s and V-8s in the late '80s / early '90s with worn bushings for the distributor shaft. The symptom was erratic idle speed due to rapidly-varying ignition timing. If that was ignored long enough you could get misfires due to the reluctor moving too far away from the pickup coil to induce a signal voltage. You would find that with a timing light. The timing marks will be bouncing around pretty badly.
Saturday, March 22nd, 2014 AT 10:50 AM