Chart C-4B Ignition System Check (Sealed Module Conn. Dist.)

Chart C-4B - Ignition System Check (Remote Coil/Sealed Module Conn. Dist.):

Wiring Diagram For Chart C-4B - Ignition System Check (Remote Coil/Sealed Module Conn. Dist.):

CHART C-4B - IGNITION SYS. CHECK (SEALED MODULE CONN. DIST.)



Test Description: Numbers below refer to circled numbers on the diagnostic chart.

1. Two wires are checked, to ensure that an open is not present in a spark plug wire.

1A. If spark occurs with EST connector disconnected, pick-up coil output is too low for EST operation.

2. A spark indicates the problem must be the distributor cap or rotor.

3. Normally, there should be battery voltage at the "C" and "+" terminals. Low voltage would indicate an open or a high resistance circuit from the distributor to the coil or ignition switch. If "C" term. voltage was low, but"+ "term. voltage is 10 volts or more, circuit from "C" term. to ignition coil or ignition coil primary winding is open.

4. Checks for a shorted module or grounded circuit from the ignition coil to the module. The distributor module should be turned "OFF", so normal voltage should be about 12 volts.


If the module is turned "ON", the voltage would be low, but above 1 volt. This could cause the ignition coil to fail from excessive heat. With an open ignition coil primary winding, a small amount of voltage will leak through the module from the "Bat," to the tach terminal.

5. Checks for an open module, or circuit to it. 12 volts applied to the module "P" terminal should turn the module "ON" and the voltage should drop to about 7-9 volts.

6. This should turn "OFF" the module and cause a spark. If no spark occurs, the fault is most likely in the ignition coil because most module problems would have been found before this point in the procedure. A module tester could determine which, is at fault.

Diagnostic Aids:

The "Scan" tool does not have any ability to help diagnose an ignition system check.

See Diagnosis By Symptoms - No Trouble Codes Stored.