It would seem unlikely that a new rotor would fail immediately -not that it's impossible. Understand this about the rotor: It's purpose is to take the spark from the coil (through the center of the rotor) and pass it along to one of the 6 cylinders that is ready to fire. It's like a rotary switch. Since it is driven by the cam, it should always be in perfect time with the crank, or position of the piston and valves. If you have a good spark from the coil, you should also have a good spark at any of the plugs -assuming the spark is enough to jump that little gap between the edge of the rotor and the conducting bit at the bottom of the cap. Also know that under the cam is a area used to control when to spark. If you had points, there would be 6 lobes to open/close the points at precisely the proper time as the cam rotates. If you have an electronic ignition conversion, there is a plastic piece with 6 magnets (or similar) for the mounted (non moving) sensor to "see". In any case, watching the spark from a wire connected to the coil results is 6 times as many sparks as from the end of the wire -but it should be very close to the same spark. Be sure the distributor is grounded, because that may cause some erratic behavior. Perhaps the sensor has moved or something is intermittent. If you really want to be sure the timing hasn't jumped, rotate the engine by hand until you can no longer hold the pressure (compression) with your finger on #1 cylinder and see if the rotor is pointing at the wire going to that cylinder. If you really want to be sure the wire is sparking, hold onto it while someone else cranks over the engine. You will know it is alive. (I don't recommend you actually do that last thing.)