Disconnect coil wire from distributor(s). Using insulated pliers, hold end of coil wire 1/2" from ground. Crank engine for 1-2 seconds. If spark is not present, go to next step. If spark is present at coil wire but not at spark plug wire, replace faulty distributor rotor, cap, wires or spark plugs as necessary.
Turn ignition off. Check for poor electrical connections at ignition coil, ignitor and distributor. Repair as necessary. If connections are okay, check resistance of coil wire and spark plug wires. Maximum allowable resistance is 25,000 ohms per wire.
If resistance is okay, turn ignition on. Disconnect ignition coil connector. Measure voltage between ground and positive terminal at ignition coil connector. See IGNITION COIL POSITIVE TERMINAL IDENTIFICATION table. If battery voltage is not present, check for open or grounded wire between battery and ignition coil or open fuse, also check for faulty ignition main relay.

If battery voltage is present, turn ignition off. Measure ignition coil resistance. To measure primary resistance, measure resistance between terminals of ignition coil. To measure secondary resistance, measure resistance between positive wire terminal at ignition coil and coil secondary tower. If resistance is not as specified, replace ignition coil. See IGNITION COIL RESISTANCE table.

IGNITION COIL POSITIVE TERMINAL IDENTIFICATION

Application	Wire Color
SC300	Black/White

IGNITION COIL RESISTANCE

Application

Primary

Secondary

SC300

Cold ⁽¹⁾

.21-.33

6400-11,100

Hot ⁽²⁾

.27-.39

8200-13,000

⁽¹⁾	Coil temperature of 14-122°F (-10-50°C).

⁽²⁾	Coil temperature of 123-212°F (51-100°C).

If resistance is as specified, check resistance across terminals of the following distributor sensor.
- Distributor pick-up coil. See Fig 1.
If resistance is not as specified, replace distributor housing. See DISTRIBUTOR SENSOR RESISTANCE table. If resistance is as specified, go to next step.
Measure air gap of pick-up coils G1, G2 and NE. See Fig 2. See DISTRIBUTOR PICK-UP COIL AIR GAP table. If air gap is within specification, go to next step. If air gap is not within specification, replace distributor.
Check ignition IGT signal from Engine Control Module (ECM). If IGT signal from ECM is defective a Diagnostic Trouble Code (DTC) should set in ECM memory. See testing procedure for DTC P1300 in TESTS W/CODES article. If IGT signal circuit is okay, substitute another ignitor and recheck system operation.

DISTRIBUTOR SENSOR RESISTANCE

Application

Ohms

SC300 (Pick-Up Coils)

Cold ⁽¹⁾

Between Terminals G1 & "G-"

125-200

Between Terminals G2 & "G-"

125-200

Between Terminals NE & "G-"

155-250

Hot ⁽²⁾

Between Terminals G1 & "G-"

160-235

Between Terminals G2 & "G-"

160-235

Between Terminals NE & "G-"

190-290

⁽¹⁾	Sensor temperature of 14-122°F (-10-50°C).

⁽²⁾	Sensor temperature of 123-212°F (51-100°C).

DISTRIBUTOR PICK-UP COIL AIR GAP ⁽¹⁾

Application

In. (mm)

SC300

.008-.020 (.20-.50)

⁽¹⁾	Not adjustable. If gap is incorrect, replace distributor housing.

Fig 1: Checking Pick-Up Coil Resistance

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

Spark Test

Use the Manual With the Right Hardware

When to See a Mechanic

Rather have a pro handle this?