Part 1 of 2

Chart C-4M Part 1 Of 2:

Chart C-4M Wiring Diagram:

CIRCUIT DESCRIPTION:

The "Integrated Direct Ignition" system (IDI) uses a waste spark method of distribution. In this type of 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 remainder of the high voltage to be used to fire # 1 spark plug. On this application, the crank sensor is mounted to, and protrudes through the block to within approximately 0.050" of the crankshaft reluctor. Since the reluctor is a machined portion of the crankshaft and the sensor is mounted in a fixed position on the block, timing adjustments are not possible or necessary.


TEST DESCRIPTION: Numbers below refer to circled numbers on the diagnostic chart.

1. This checks for equal relative power output between the cylinders. Any injector which when disconnected did not result in an rpm drop approximately equal to the others, is located on the misfiring cylinder.

2. If a plug boot is burned, the other plug on that coil may still fire at idle. This step tests the system's ability to produce at least 25,000 volts at each spark plug,

3. No spark, on one coil, may be caused by an open secondary circuit. Therefore, the coil's secondary resistance should be checked. Resistance readings above 20,000 ohms, but not infinite, will probably not cause a no start but may cause an engine miss under certain conditions.

4. If the no spark condition is caused by coil connections, a coil or a secondary boot assembly, the test light will blink. If the light does not blink, the fault is module connections or the module.

5. An injector driver circuit shorted to ground would result in the test light "ON" steady, and possibly a flooded condition which could damage engine. A shorted injector (less than 2 ohms) could cause incorrect ECM operation.

DIAGNOSTIC AIDS:

Verify IDI connector terminal "K", CKT 450 resistance to ground is less than 0.5 ohm. A shorted or low resistance injector may cause a miss in the other injector in that pair. (1&4 or 2&3).