Replace the cap & rotor as a set always. You will need to check for spark. Then look for why there is no spark in the wiring, voltages and such. Only after confirming the spark from the coil and still no spark to the plugs would it be time to look at the igniter itself. The trigger in the EI is what energizes the coil to send a spark through the distributor. The EI is the last check.
Dave Neptune