Use a 12 volt test light at the battery wire going into the distributor cap. With the ignition switch on, you should have voltage there. Then move the test light to the "Tach" terminal right next to the battery wire. It should also have steady voltage with the key on and the engine stopped, but it should change to a pulsating flash on the test light while cranking. If it stays steady while cranking, you've got a bad module or pickup coil. If it's flashing while cranking, the pickup coil and the module are good. If there's still no spark, it's a bad rotor or coil. The older rotors had a bad habit of burning a hole in the center, and sending all the spark to the distributor shaft, none to the plugs. Since you've changed the rotor, that's probably not the problem unless you put another bad one in.
Checking the pickup coil:
Unplug the yellow 2-wire connector from the module, and use a low-reading digital voltmeter on the AC volts scale. While cranking, you need at least 1/2 volt at the plug terminals. With the distributor out of the engine, this voltage can be checked by simply spinning the distributor shaft. The voltage is generated by magnetism without any input from the vehicle electrical system. You can also check out the whole ignition system with the distributor removed. Use the whole distributor, cap and all, with the plug wires removed. Be sure the 3-wire plug from the distributor housing to the cap is connected. Just put 12V power to the Bat. terminal on the cap and ground to the distributor housing, with the distributor mounted in a vise. Take the coil cover off, and spin the shaft. Sparks will jump from the plug terminals to the coil housing. Quick, easy, and it checks out the whole system. Those sparks are about 50,000 Volts, so don't get bit!
Jerry
