Here are some diagnostic procedures:
Secondary Spark Test:
The best way to perform this procedure is to use a spark tester (available at most automotive parts stores). Two types of spark testers are commonly available. The neon bulb type is connected to the spark plug wire and flashes with each ignition pulse. The air gap type must be adjusted to the individual spark plug gap specified for the engine. This type of tester allows the user to not only detect the presence of spark, but also the intensity (orange/yellow is weak, blue is strong).
1. Disconnect a spark plug wire at the spark plug end.
2. Connect the plug wire to the spark tester and ground the tester to an appropriate location on the engine.
3. Crank the engine and check for spark at the tester.
4. If spark exists at the tester, the ignition system is functioning properly.
5. If spark does not exist at the spark plug wire, remove the distributor cap and ensure that the rotor is turning when the engine is cranked.
6. If the rotor is turning, perform the spark test again using the ignition coil wire.
7. If spark does not exist at the ignition coil wire, test the ignition coil, and other distributor related components or wiring. Repair or replace components as necessary.
Primary Circuit Continuity:
1. Separate the wiring harness connector from the ignition module.
2. Attach the negative lead of a Digital Volt Ohmmeter (DVOM) to the base of the distributor and the positive lead to the battery positive terminal. Measure and note the battery voltage reading.
3. Insert a straight pin into connector terminal No. 2, attach the positive lead of the DVOM to the straight pin and the negative lead to the distributor base.
4. Turn the ignition key to the RUN position and measure the voltage. The voltage reading should be at least 90% of the battery voltage.
5. If the voltage reading is less than 90% battery voltage, perform the ignition coil primary voltage test in this section.
6. Turn the ignition switch OFF and remove the straight pin.
Ignition Coil Primary Circuit Switching
1. Unplug the wiring harness from the ignition coil. Check the harness for dirt, corrosion or damage.
2. Attach a 12 volt DC test light between the coil TACH terminal and a good engine ground.
3. Crank the engine and observe the lamp.
4. If the lamp flashes or lights without flashing, go to the ignition coil primary resistance test in this section.
5. If there is no light or a very dim light, perform the primary circuit continuity test in this section.
Ignition Coil Primary Voltage:
1. Attach the negative lead of a Digital Volt Ohmmeter (DVOM) to the base of the distributor and the positive lead to the battery positive terminal. Measure and note the battery voltage reading.
2. Turn the ignition key to the RUN position and attach the positive lead of the DVOM to the negative ignition coil terminal. Note the voltage reading and turn the ignition OFF.
3. If the voltage reading is less than 90% battery voltage, inspect the wiring between the ignition module and the negative coil terminal.