Electronic Spark Control Module: Testing and Inspection

Use the following procedures to diagnose ESC system malfunctions only. To diagnose general ignition system malfunctions, refer to ``High Energy Ignition (HEI) System Diagnosis.''

Fig. 4 ESC system wiring schematic. 1983:

1983 MODELS

Engine Cranks But Will Not Start

1. Inspect ESC harness for damage, shorts and opens. Inspect controller connector, distributor connectors and ignition switch connectors for corrosion, damage and deformed terminals, Fig. 4. Repair connectors and wiring as needed.
2. Disconnect distributor 4 pin connector, connect pins A and C on distributor side of connector with jumper wire, then attempt to start engine. If engine fails to start, refer to HEI system diagnosis; if engine starts, proceed to next step.
3. Remove jumper wire and reconnect connector to distributor. Turn on ignition, then measure voltage between pins F and K in the ESC controller 10 pin connector. If reading is less than 7 volts, check circuit between controller and ignition switch and repair as needed. If voltage is greater than 7 volts, proceed to next step.
4. Inspect wiring from ESC controller terminals G, H, J and K, and repair if damaged shorted or open. If wiring is satisfactory, but engine still will not start, ESC controller is defective.

Poor Engine Performance

1. Disconnect distributor 4 pin connector, connect pins A and C on distributor side of connector with jumper wire, Fig. 4, and road test vehicle.
2. If engine performance is still poor, cause is not in ESC system. If proper engine performance is restored by disconnecting ESC controller from distributor, remove jumper wire, reconnect 4 pin connector and proceed to next step.
3. Connect pins A and B on ESC controller connector , leaving connector in place, then road test vehicle. If proper engine performance is restored, proceed to step 5 or 6.
4. If engine performance is still poor with jumper between controller terminals A and B, proceed as follows:
a. Remove jumper wire from controller terminals A and B.
b. Start engine and measure voltage between between pins F and K of ESC controller. If reading is less than 11.6 volts, check charging system and repair as needed.
c. If voltage between terminals F and K is greater than 11.6 volts, check wiring to ESC controller and repair as needed. If wiring is satisfactory, ESC controller is defective.
5. On 1983 models, proceed as follows:
a. Remove jumper wire from controller terminals A and B.
b. Set engine to run at approximately 2000 RPM, disconnect electrical connector from knock sensor and measure voltage between sensor terminal and ground.
c. If voltage is not .08 volt or greater, knock sensor is defective. If voltage is .08 volt or greater, inspect wiring to pins A, B and K of controller and repair as needed. If wiring is satisfactory, controller is defective.



Engine Detonation

1. Connect suitable timing advance tester to engine, run engine until it reaches normal operating temperature and set engine to run at 1000 RPM, then repeatedly tap on exhaust manifold while observing ignition timing. If timing retards while tapping on manifold, system is operating normally.
2. If timing does not retard on 1983 models, proceed as follows:
a. Disconnect 10 pin connector from ESC controller and measure voltage between connector terminals B and K with engine running at 2000 RPM. Voltage reading should be .08 volt or greater.
b. If voltage is as specified, proceed to step 4.
c. If voltage is not as specified, repeat voltage check at knock sensor. If voltage is .08 volt or greater, repair wiring between knock sensor and controller. If voltage is not .08 volt or greater, knock sensor is defective.
3. With 10 pin ESC controller disconnected, attempt to start engine. If engine starts, replace HEI module; if engine does not start, proceed to next step.
4. Reconnect 10 pin connector to ESC controller, connect suitable spark advance tester to engine and disconnect electrical connector from knock sensor.
5. Run engine at fast idle and jump terminals of knock sensor connector while observing ignition timing. If timing retards, knock sensor is defective.
6. If timing does not retard when sensor connector is jumped, measure voltage between terminals H and K at controller with ignition on. If reading is less than .2 volt check wiring top controller terminal H and repair as needed. If voltage is greater than .2 volt, controller is defective.