NOTE: Before making this check, always check ignition coil primary circuit first.

Disconnect 2-wire connector at control unit. Connect voltmeter negative lead to ground and positive lead to Red wire harness connector terminal "F2". Turn ignition switch on. Voltage reading should be battery voltage (within 0.2 volts). If reading is correct, replace control unit. If not, proceed to next step.
Locate and repair cause of voltage reduction (corroded connectors, defective ignition switch, etc.). If connectors are repaired and there is spark at coil wire, start engine. If connectors are repaired and there is no spark at coil wire, replace control unit.
Connect voltmeter negative lead to ground and positive lead to Light Blue wire at harness connector terminal "F1" in 2-wire connector. Crank engine. Voltmeter reading should be within 1 volt of battery cranking voltage. If not, check for bad connections, ignition switch or starter solenoid.

Fig 1: Exploded View of Jeep SSI Distributor Reluctors have 1 tooth for each cylinder.
Turn ignition switch off, connect 2-wire connector and disconnect 4-wire connector. Connect an ammeter to ground and to Black wire terminal "C1" of control unit (not harness) connector. Turn ignition switch on. Reading should be 0.9-1.1 amps. If reading is higher or lower than specified, replace control unit.

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

Control Unit Power Feed Check