Available Spark

Crank engine and check for a strong Blue spark at coil wire and each spark plug wire using Spark Tester (ST-125). If spark tester is not available, check for spark by holding wire terminal 5/16" from ground while cranking engine.
If spark does not occur, check ignition coil, ignitor and distributor connections. If connections are good, use an ohmmeter to check resistance of high-tension wires. See HIGH TENSION WIRE RESISTANCE table. If resistance is not within specification, replace wires.
Check for voltage at ignition coil positive terminal. If voltage is not present, check wiring between ignition switch, coil, and ignitor. If voltage is present, check ignition coil resistance. See IGNITION COIL RESISTANCE table. If ignition coil resistance is incorrect, replace coil.
If ignition coil resistance is correct, check pick-up coil resistance. See PICK-UP COIL RESISTANCE table. If pick-up coil resistance is incorrect, replace pick-up coil or distributor. If resistance is within specification, check air gap between reluctor and pick-up coil. See PICK-UP COIL AIR GAP table.
If air gap is incorrect, repair as necessary. If air gap is correct, check ignition signal from ECU. See appropriate trouble code chart in TESTS W/CODES article. If signal is okay, replace ignitor.

Fig 1: Exploded View Of Typical Distributor Assembly (Spectrum Is Shown)

Courtesy of GENERAL MOTORS CORP.