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Ignition System Check: Notes

NOTE: Before testing, obtain Spark Tester (ST-125). If tachometer is connected to ignition coil "TACH" terminal, disconnect it before performing tests. Use digital voltmeter with 10 megaohms or greater impedance.
CAUTION: When removing spark plug wire from spark plug, twist and pull on boot, NOT on wire. Integrally Mounted Ignition Coil
  1. Remove any spark plug wire and attach Spark Tester (ST-125). Check for spark while cranking engine. If there is no spark, check a second wire in same manner. If there is still no spark, proceed to step 2). If spark occurs, ignition system is not at fault. Check fuel system, and spark plugs.
  2. Disconnect 4-wire EST connector between distributor and ECM. Check for spark at tester. If spark is present, replace pick-up coil.
  3. If no spark occurred with 4-wire plug disconnected, check voltage at distributor "BATT" terminal while cranking engine.
  4. If step 3) reading was less than 7 volts, repair primary circuit back to ignition switch. If 7 volts or more, leave negative lead grounded and check voltage at "TACH" terminal.
  5. If step 4) reading was less than 1 volt, ignition coil or ignition coil connector is defective. Repair or replace as necessary. If reading is 10 volts or more, proceed to step 7).
  6. If "TACH" terminal voltage was between 1 and 10 volts, replace distributor HEI (EST) module and check for spark. If a spark results, ignition system is functioning. If there is still no spark, replace ignition coil.
  7. If "TACH" terminal voltage in step 5) was 10 volts or more, attach Spark Tester (ST-125) to coil output terminal. Crank engine and check for spark. If no spark occurs, proceed to step 9).
  8. If spark occurs, check color match of pick-up coil connector and ignition coil lead. Inspect cap for water, cracks or other damage. If no damage is noted, replace rotor.
    NOTE: Ignition coils with Red and White leads should be matched with pick-up coils having either a Clear, a Black, or Blue connector. Ignition coils with Red and Yellow leads must be matched with pick-up coils with Yellow connector.
  9. Remove pick-up coil leads from module. Connect positive lead of voltmeter to coil "TACH" terminal and negative lead to ground. Turn ignition switch to "ON" position. Connect one lead of test lamp to battery positive terminal. Quickly, and for less than 5 seconds, connect other lead to HEI (EST) module terminal "P". Watch voltmeter as test lamp touches terminal.
  10. If voltage drops, proceed to step 11). If voltage does not drop, check module ground screw. Also check for open circuits in wires from distributor cap (coil) to distributor. If okay, replace HEI (EST) module.
  11. Check for spark with spark tester when test light is removed from module terminal. If spark occurs, the pick-up coil or its connections are defective. Perform Distributor Pick-Up Coil Short and Resistance Check.
  12. Ensure ignition coil is properly grounded. Use Distributor Module Tester (J-26792) to check HEI (EST) module. Replace module if defective. Otherwise, replace ignition coil.
  13. If no module tester is available, replace ignition coil and repeat steps 7), 9), and 11). If spark results, problem was faulty ignition coil. If no spark results, original ignition coil is probably good. Reinstall original ignition coil and replace HEI (EST) module.
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