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Home >> Chevrolet >> 1986 >> Forward Control 6.2 J, Automatic, 475/M40 >> Repair and Diagnosis >> Engine Performance >> Ignition System >> Ignition System - HEI-Est (CALIF) >> Testing >> Ignition System Check

Ignition System Check

NOTE: If tachometer is connected to ignition coil "TACH" terminal, remove before performing tests. Use a digital voltmeter with 10 megohms impedance or higher.
  1. Remove spark plug wire and attach Test Plug (J-26792) to wire. Crank engine and check for spark. If spark occurs, ignition system is not at fault. Inspect fuel system or spark plugs.
  2. If no spark occurred, separate 4-pin connector at distributor. Connect terminals "A" and "C". If engine starts, proceed to step 5). If engine does not start, reconnect 4-pin connector. With ignition switch in the "ON" position, measure voltage at terminals "F" and "K" of the 10-pin connector.
  3. If reading is under 11.6 volts, locate and repair excessive resistance in system. If voltage is over 11.6 volts, set volt meter on 2-volt scale to probe circuit from pin "J" to "K" while cranking engine. If voltage is .75 volts or higher, system is okay.
  4. If there is no voltage, attach voltmeter probes to pins "G" and "H". Set scale on 2-volt range and crank engine. If meter reads 200 millivolts or more, replace the ECM unit. If less than 200 millivolts, replace pole piece.
  5. If engine started in step 2), stop engine and attach high resistance test lamp from tachometer terminal to ground. If lamp lights, crank engine. System is okay if lamp flickers. If not, attach test lamp from ignition coil positive terminal to pin "A" of distributor 4-pin connector.
  6. Coil should "click" when tapped lightly. If not check pole piece connection for good contact. If pole piece connections are good and coil does not "click" when tapped, replace distributor module.
  7. If module is not replaced, separate pick-up coil connector from module and turn ignition on. Check voltage at module terminal "C". Watch voltmeter as a test light is momentarily connected (not more than 5 seconds) between battery positive terminal and module terminal "P".
  8. If no voltage drop occurs, check for open in wiring between coil and distributor and module ground. If okay, replace module. If voltage dropped, check for spark at tester gap (attached to coil secondary terminal) when test light is removed from module "P" terminal. If spark occurs, replace pick-up coil.
    NOTE: Perform DISTRIBUTOR PICK-UP COIL SHORT and RESISTANCE CHECKS if not done previously. See Figure.
  9. If no spark occurs, use module tester to check distributor module. Replace module if defective. If okay, check ignition coil ground and wiring to distributor. If okay, replace ignition coil.
  10. If module tester is not available, replace module and repeat step 9). If spark results, system is okay. If spark does not result, original module is okay. Reinstall module and replace coil.
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