Hi there,

I suggest you;
Test the distributor cap With the meter set to measure OHM's (resistance) measure the resistance from each terminal one at a time with one probe in the centre of a terminal at the outside - and the other probe on the same terminal inside the cap. RESISTANCE SHOULD BE: 700 to 1300 OHM's

Test the rotor at the middle (where is contacts the centre cap terminal) to the outer peak. RESISTANCE SHOULD BE: 700 to 1300 OHM's

Test ignition cables and the spark plug connectors RESISTANCE AGAIN SHOULD BE: 700 to 1300 OHM's

Also your suspect main cable from the coil to dist cap.

Replace any component outside these specs.

Good luck,
Acky