Ignition System Check
- Disconnect a spark plug wire and connect Spark Tester (ST-125). Check for spark while cranking engine. If no spark occurs, check for spark at another wire. Intermittent sparks are considered no spark. If no spark occurs, proceed to step 2). If spark occurs, problem is in fuel system or spark plugs.
- Unplug 4-terminal EST connector. Check for spark at tester. If spark occurs, replace pick-up coil. If no spark occurs, check for spark at coil wire with Spark Tester (ST-125) while cranking engine.NOTE: Leave Spark Tester (ST-125) connected during remainder of tests.
- If spark is present while cranking, inspect cap for cracks or other defects. If okay, replace rotor. If no spark occurs while cranking, disconnect distributor 2-wire "C/+" (coil) connector. Turn ignition on and check voltage at "C" and "+" terminals of harness connector.
- If there is less than 10 volts at terminal "C" only. Check for open or ground in circuit from "C" to ignition coil. If circuit is okay, fault is with ignition coil or connections. If both terminals read less than 10 volts, proceed to step 5). If both terminals read 10 volts or more, proceed to step 6).
- Repair wire from module "+" terminal to "B" terminal of Black ignition coil connector or primary circuit to ignition switch.
- Reconnect distributor 2-wire connector. Check voltage from "TACH" lead to ground with ignition on.
- If voltage is less than one volt in step 6), repair open tachometer lead or connector and repeat step 6). If voltage reading is 1-10 volts in step 6), replace module and check for spark as described in step 12). If spark is present, system is good. If no spark occurs, replace ignition coil.
- If voltage is more than 10 volts in step 6), connect test light from "TACH" lead to ground. Crank engine and observe light. If light blinks, replace ignition coil and recheck for spark with Spark Tester (ST-125). If no spark, install original coil and replace module.
- If light remains steady in step 8), unplug distributor 4-wire connector. With ignition on, remove distributor cap and retaining screw in 4-wire end of module.
- Loosen remaining module screw and pivot module out to gain access to pick-up coil terminals. Connect jumper from module retaining screw eyelet to ground See Fig 1. Disconnect pick-up coil from module. Connect voltmeter between "TACH" terminal and ground.
- Insulate test light probe to 1/4" from tip. Note voltage as test light is momentarily connected between module terminal "P" and 1.5 to 8 volt source. See Fig 1. To ensure against module damage, DO NOT allow test light to be connected for more than 5 seconds.
- If there is no voltage drop. Ensure module is properly grounded. If good ground is noted, replace module. If voltage drops, check for spark at coil wire with Spark Tester (ST-125) when test light is removed from module terminal "P".
- If spark is present in step 12). On all engines except 2.5L S/T series. Ensure rotating pole piece is still magnetized, check pick-up coil resistance and connections (coil resistance should be 500-1500 ohms and not grounded).
- If rotating pole piece is not magnetized, replace pole piece and shaft assembly. If spark is present in step 12) on 2.5L S/T series engines, check pick-up coil resistance and connections (coil resistance should be 500-1500 ohms and not grounded).
- On all engines, if no spark occurs in step 12) check module with Module Tester (J24642). Replace module if defective. Check coil wire between cap and coil. If wire is okay, replace coil.
- If Module Tester (J24642) was not available in step 14), replace ignition coil and repeat step 9). If spark is present, system is okay. If no spark is present, original ignition coil was okay. Reinstall original coil and check coil wire. If coil wire is okay, replace module.