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. A few sparks and then nothing is considered no spark. If spark results, problem is in fuel system or spark plugs.
2. If no spark occurred in step 1, unplug 4 terminal EST connector. Check for spark. If spark, replace pick-up coil. If no spark, check for spark at coil wire with Tester (ST-125) while cranking.
   NOTE: Leave spark tester (ST-125) connected during remainder of tests.
3. If spark is present while cranking, inspect cap for cracks or other defects. If okay, replace rotor. If 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 at terminal "C", 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 reading was 1-10 volts 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, also replace ignition coil.
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, check coil wire from distributor cap. If good, replace ignition coil and repeat step 7.
10. If spark occurs, system is operating properly. If no spark occurs, coil removed is okay. Reinstall original coil and replace module.

(Sealed Module Connector Distributor)

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. A few sparks and then nothing is considered no spark. If spark results, problem is in fuel system or spark plugs.
2. If no spark occurred in step 1, unplug 4-terminal EST connector. Check for spark. If spark, replace pick-up coil. If no spark, check for spark at coil wire with Tester (ST-125) while cranking engine.
   NOTE: Leave spark tester (ST-125) connected during remainder of tests.
3. If spark is present while cranking, inspect cap for cracks or other defects. If okay, replace rotor. If no spark while cranking, unplug distributor 2-wire "C/+" (coil) connector. Turn ignition on with engine stopped. Check voltage at "+" and "C" terminals of harness connector.
4. If under 10 volts at terminal "C" only, check for open or ground in circuit from "C" to ignition coil. If circuit good, fault is ignition coil or connections.
5. If both terminals read under 10 volts in step 3, repair wire from module "+" terminal to "B" terminal of Black ignition coil connector or primary circuit to ignition switch.
6. If both terminals read 10 volts or more in step 3, check voltage from "TACH" lead to ground with ignition on. Reconnect distributor 2-wire connector.
7. If voltage less than 1 volt in step 6, repair open tachometer lead or connector and repeat step 6. If voltage reading is 1-10 volts in step 6, replace module and check for spark as described in step 1. If spark present, system is good. If no spark, replace ignition coil also.
8. If voltage is over 10 volts in step 6, connect test light from "TACH" lead to ground. Crank engine and observe light. If light blinks, replace ignition coil and recheck for spark with tester (ST-125). If still no spark, install original coil an replace module.
9. If light is on steady in step 8, unplug distributor 4-wire connector. With ignition on, remove distributor cap and 5 mm retaining screw in 4-wire end of module.
10. Loosen remaining module screw and pivot module out to gain access to pick-up coil terminals. Jumper module retaining screw eyelet to ground. Disconnect pick-up coil from module. Connect voltmeter from "TACH" terminal to ground. Insulate test light probe to 1/4" from tip. Note voltage as test light is momentarily connected from module terminal "P" to 12 volt source. DO NOT  touch for more than 5 seconds.
11. If no drop in voltage, check module ground. If ground good, replace module. If voltage drops, check for spark from coil wire with spark tester (ST-125) as test light is removed from module terminal.
12. If spark is present in step 11, check pick-up coil resistance or connections. If no spark, check module with module tester. Replace module if defective. If module is good, check coil wire from cap to coil. If wire good, replace coil.
13. If no module tester was available in step 12, replace ignition coil and repeat step 9. If spark is now present, system is good. If no spark present, ignition coil removed is OK. Install coil and check coil wire from cap. If coil wire OK, replace module.