You aren't listening. If the car runs you have confirmed two things. The first is that the crank sensor did its job. The second is that the ignition control module EZL did its job creating the DC pulse signal call TN (engine speed). This TN signal is what runs the tach.

There is NO memory and NO reset on an 87.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician