Chart C-4F-2 Misfire Under Load (C3I Ignition System)

Chart C-4F-2 - C3-I Misfire Under Load:

Wiring Diagram for Chart C-4F-2 - C3-I Misfire Under Load:

CHART C-4F-2 - C3-I MISFIRE UNDER LOAD

Circuit Description:

The C3-I uses a waste spark method of spark distribution. In this type of ignition system the ignition module triggers the # 1/4 coil pair resulting in both # 1 and # 4 spark plugs firing at the same time. # 1 cylinder is on the compression stroke at the same time # 4 is on the exhaust stroke, resulting in a lower energy requirement to fire # 4 spark plug. This leaves the remaining high voltage to fire # 1 spark plug.




Test Description: The following numbered steps correspond with the step numbers on the diagnostic chart.

1. If the "misfire" complaint exists at idle only, Chart C4F-1 must be used. A spark tester such as a ST-125 must be used because it is essential to verify adequate available secondary voltage at the spark plug (25,000) volts). Spark should jump the tester gap on all 6 leads. This simulates a "load" condition.

2. By grounding the opposite plug lead of the affected coil, a faulty spark plug (extremely high resistance) may be detected.

3. If ignition coils are carbon tracked, the coil tower spark plug wire nipples may be damaged.

4. By switching a normally operating coil into the position of the malfunctioning one, a determination can be made as to fault being the coil or C3-I module.

5. A shorted coil could cause repeat C3-I module failures.