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Home >> Cadillac >> 1988 >> Seville Base >> Repair and Diagnosis >> Engine Performance >> Ignition System - HEI-Est >> Testing >> Ignition System Check >> Integrally Mounted Ignition Coil

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 at other wires 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, spark plugs and engine mechanical condition for cause of a no-start condition.
  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 "BAT" terminal while cranking engine.
  4. If "BAT" terminal reading was less than 7 volts, repair primary circuit back to ignition switch. If reading was 7 volts or more, leave negative lead grounded and check voltage at "TACH" terminal.
  5. If "TACH" terminal reading was less than one 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 1-10 volts, replace distributor HEI/EST module and check for spark with spark tester connected as described in step 7) . If a spark occurs, ignition system is functioning. If there is 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 inside distributor cap using a modified spark plug boot. Using a jumper wire, ground the spark tester. See Fig 1. Crank engine and check for spark. If no spark occurs, proceed to step 9).
    NOTE: Leave Spark Tester (ST-125) connected in this manner during remainder of tests.
  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 "BAT" lead and White "TACH" lead should be matched with pick-up coils having either a Clear, Black or Blue connector. Ignition coils with Red "BAT" lead and Yellow "TACH" lead 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 lead of test light to battery positive terminal. Touch test light probe (maximum of 5 seconds) to HEI/EST module terminal "P". Watch voltmeter as test light touches terminal.
  10. If voltage drops, proceed to step 11). If voltage does not drop, check module ground. Also check for open circuits in wires from distributor coil to HEI/EST module. If okay, replace HEI/EST module.
  11. Using spark tester still connected as in step 7), check for spark 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 & RESISTANCE CHECKS  in this article.
  12. Ensure ignition coil is properly grounded. Use Distributor Module Tester (J-26792) to check HEI/EST module. Replace module if defective. If module tests okay, test coil wire and replace if necessary. If coil wire tests okay, replace ignition coil.
  13. If no module tester is available, replace ignition coil with a known good unit and return to step 11). If spark occurs, problem was faulty ignition coil. If no spark occurs, original ignition coil is okay. Reinstall original ignition coil and replace HEI/EST module.
Fig 1: Integral Coil Spark Tester (ST-125) Hook-Up
G54463
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