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Home >> Pontiac >> 1984 >> Fiero Base, Automatic >> Repair and Diagnosis >> Engine Performance >> Ignition System - HEI-Est >> Testing >> Ignition System Check >> Externally Mounted Ignition Coil
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Externally Mounted Ignition Coil

  1. Remove a spark plug wire and connect spark tester. Check for spark while cranking engine. If no spark results, check for spark at another wire. If spark results, problem is in fuel system or spark plugs.
  2. If no spark OCCURRED in step 1, unplug 4 terminal EST connector. Start engine. If engine runs, go to EST System Check. If engine will not run, check for spark at coil wire with ST-125 while cranking.
  3. If spark is present while cranking, inspect cap for cracks or other defects. If okay, replace rotor. If there is no spark while cranking, remove distributor cap with ignition "ON". Check voltage at HEI-EST module terminal "+".
  4. If voltage is less than 10 volts, repair wire from terminal "+" to ignition coil and primary circuit to ignition switch.
  5. If voltage was 10 volts or more in step 3, leave ignition switch "ON". Check voltage at HEI-EST module terminal "C". If voltage is less than 1 volt, check for open or grounded lead from ignition coil to terminal "C". Also check ignition coil connections or for an open primary circuit in ignition coil.
  6. If voltage was 1-10 in step 3, replace HEI-EST module and check for spark from ignition coil. If sparks occur, system is operating properly. If no sparks occur, replace ignition coil as it too is defective.
  7. If voltage was 10 volts or more in step 5, remove pick-up coil connector from HEI-EST module. Check voltage at HEI-EST module terminal "C" with ignition switch "ON". Momentarily connect a test light between battery voltage and HEI-EST module terminal "P" while observing voltmeter.
  8. If voltage does not drop, check HEI-EST module ground. If okay, replace HEI-EST module. If voltage drops, use a spark tester and check for spark at end of coil wire as test light is removed from module terminal "P". If spark does occur, check pick-up coil and its connections. Ensure pick-up coil is not grounded.
  9. If no spark occurs in step 8, check HEI-EST module with tester (J-26792). Replace module if defective. If module okay, check coil wire from distributor cap to ignition coil. If coil wire okay, replace ignition coil. If no distributor module tester is available, replace the HEI-EST module and repeat step 8.
  10. If spark occurs, system is operating properly. If no spark occurs, HEI-EST module removed is okay. Reinstall original module and check secondary wire from distributor cap to ignition coil. If okay, replace ignition coil.
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