A car engines Ignition System with distributor type ignition systems can seem complex, but once simplified can be diagnosed with ease. Using the Diagram provided above you can see there are several different components. The most common component is the spark plug. If you do not have spark at the spark plug then you can backtrack from there. Use a new spark plug or spark tester to test for spark coming from the plug wire, if you do not see spark here, test for spark coming from the coil wire to the distributor. If these test ok, move on and look at the distributor cap and rotor for corrosion or damage. If these look ok, then you most likely have a failed ignition module. The ignition module is located under the distributor cap on GM vehicles and external on most other vehicles. Ignition module failure is the most common no spark symptom outside normal tune up maintenance.