I wrote this before but here goes. Remove four wire connector from distributor. Turn key to on position. test the wires on the harness side for the following:
Black wire---Ground
Red wire-----Battery voltage
White wire---5 volts
Green wire---5 volts
If all is good, reconnect connector and crank engine while monitoring the white and then the green wire. Both should toggle between 0 and 5 volts. A digital meter will average this signal and display 2.5 volts.
Conner

Over the hill but still climbing.
88 Montero 2.6L auto, manual hubs, cooling fan conversion gps,recurved distributor,LSD Diff.