By-Pass Or Faulty Est Check

With engine at fast idle, check timing. Ground test terminal and note if timing changes. If timing does change, system is operating properly. If timing does not change, stop engine and disconnect 4-wire EST connector from distributor.
Connect a jumper wire from terminal "A" to "B" on distributor side of EST connector. See Fig 1. Start engine, ground test terminal and connect test light from battery positive terminal to terminal "C" of EST connector.

Fig 1: Test Light Hook-Up for Checking EST Emission System
If engine stops, check for open wire from EST terminal "E" to ECM. If wire is okay, replace either HEI-EST connector or module. If engine runs, remove jumper wire from terminals "A" and "B" while leaving test light connected. If engine runs, proceed to step 4. If engine stops, proceed to step 5.
If engine continued to run in step 3), check distributor wires for open or ground to HEI-EST module terminal "B" or short between module terminals "R" and "E". If wires are okay, repair faulty HEI-EST module connection or replace HEI-EST module.
If engine stopped in step 3), check for open wire from EST connector terminal "A" to ECM connector terminal "12". Also check for open or grounded wire from EST connector terminal "C" to ECM connector terminal "11". If wires are okay, replace faulty ECM connector or ECM.

NOTE: ECM connector terminal numbers may vary between models.