Ignition System: Service Precautions
TFI IV
Do not change timing by use of different octane rods without first having the proper authorization as federal emission requirements will be affected.
Except for the cap, rotor, module, O-ring, and octane rod, no other distributor assembly parts are replaceable. There is no calibration required with the universal distributor.
Do not attempt to lift module from mounting surface prior to moving entire TFI module toward distributor flange as you will break the pins at the distributor/module connector.
The rotor is a multi-point rotor which eliminates the need for silicone compound on the rotor tip.
Some engines may be equipped with a security type distributor holddown bolt. Use Tool T82L-12270-A or equivalent to remove the distributor.
CIRCUIT TESTS - TFI IV
The primary winding of the ignition coil may be damaged if there is a short to ground in the wiring harness containing the tachometer circuit. Before replacing the ignition coil due to a no start condition, measure and record battery voltage as well as voltage between coil negative terminal and ground with ignition key in the On position. If there is more than a 1 volt difference between the readings, inspect tachometer circuit for a short to ground and repair as necessary.
If a short to ground is caused by a failed TFI-IV module, the ignition coil primary winding may be damaged. Because this type of malfunction will not be identified using standard testing procedures, the following steps should be taken when servicing a weak or no spark condition: check for spark as described in ``Test 1.'' If there is no spark, test coil primary resistance as described in ``Test 3.'' If coil primary resistance is satisfactory, continue with diagnostic procedure described in ``Test 1.'' If coil primary resistance is not satisfactory, replace coil and recheck for weak or no spark. If spark is now satisfactory, the problem no longer exists. If spark is still not satisfactory, continue with diagnostic procedure described in ``Test 1.''
DIS SYSTEM
FAILURE MODE EFFECTS MANAGEMENT (FMEM)
During some DIS faults, the FMEM portion of the DIS ignition module will maintain vehicle operation. The DIS module will automatically turn the ignition coils on and off using the profile ignition pickup (PIP) signal if it does not receive the Spout (Spark Out) input. This condition will result in fixed spark and fixed dwell timing. If the module does not receive the Cylinder Identification (CID) input, random coil synchronization will be attempted by the module. Several attempts may be required to start the engine when the DIS module is in this mode.
SYNCHRONIZER ASSEMBLY
Prior to starting the removal procedure, set cylinder No. 1 to 26 degrees (ATDC) of the compression stroke. Then note the position of the camshaft sensor electrical connector. This procedure requires that the connector be located in the same position.
A tool such as Syncro Positioner T89P-12200-A or equivalent must be obtained prior to installation if the replacement synchronizer does not contain a plastic locator cover tool. Failure to follow this procedure will result in improper alignment, which will cause the ignition and fuel system to be out of time with the engine, thus causing possible engine damage.
DO NOT reposition the connector by rotating the synchronizer base if the camshaft sensor electrical connector is not properly positioned. (Forward of the supercharger drive belt or contacting the A/C bracket) This will cause the fuel and ignition system to be out of time with the engine, causing possible engine damage. Instead, remove synchronizer and repeat installation procedure.
SPARK PLUG WIRES
Proper installation of spark plug wires is critical to vehicle operation. If one spark plug wire is not properly installed on spark plug or ignition coil, both spark plugs connected to ignition coil may not fire under load.