Chart C4B - Ignition System Check
NOTE:
The following step numbers refer to the numbers in the accompanying flow chart(s).
- 1) The 2 wires are checked to ensure that an open is not present in a spark plug wire.
- 1A) If spark occurs with 4 terminal distributor connector disconnected, pick-up coil output is too low for EST operation.
- 2) A spark indicated that the problem must be the distributor cap or the rotor.
- 3) Normally, there should be battery voltage at both the "C" and "+" terminals. Low voltage indicates an open or a high resistance circuit from the distributor to coil or ignition switch. If the "C" terminal voltage was low, but "+" terminal voltage is 10 volts or more, circuit from "C" terminal to ignition coil or ignition coil primary winding is open.
- 4) Checks for a shorted module or grounded circuit from ignition coil to 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 one (1) volt. This could cause ignition coil to fail from excessive heat. With an open ignition coil primary winding, a small amount of voltage will leak through module from "Bat" terminal to tach terminal.
- 5) Applying a voltage (1.5-8 volts) to module terminal "P" should turn module on, and tach terminal voltage should drop to about 7-9 volts. This test will determine whether module or coil is faulty or if pick-up coil is not generating proper signal to turn module on. This test can be performed by using DC battery with to rating of 1.5-8 volts. The use of test light is mainly to allow "P" terminal to be probed more easily Some digital multi-meters can also be used to trigger module by selecting ohms, usually the diode position. In this position, the meter may have voltage across it's terminals, which can be used to trigger module. The voltage in ohm's position can be checked by using a second meter or by checking the manufacture's specification of tool being used.
- 6) This should turn off module and cause a spark. If no spark occurs, fault is most likely in ignition coil because most module problems would have been found before this point in procedure. A Module Tester (J24642) could determine which is at fault.