If its electronic and in the dizzy it is called the crank angle sensor. It ultilizes a special optical based rotor and sensor. This part is pricy and is the only "real" electonic component in the distributer. It is located under the rotor, under the dust cover. I think its commonly called the crank angle sensor, ignition control module, or ignition pickup. Im not familar with testing this piece other then replacing it though, sorry.

87 Dodge Raider 4.3 Vortec work in progress
89 Dodge Raider 3.0 V6 Fully Restored
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