Spark Test

NOTE: SC400 have 2 distributors and 2 ignition coils. Distributors are located at front end of each cylinder head, under cover.

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, 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. 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. Check voltage at positive terminal (Black/Orange wire) of ignition coil connector. If battery voltage is not present, check for open or grounded Black/Orange wire or open fuse.
If battery voltage is present, turn ignition off. Measure ignition coil resistance. See IGNITION COIL RESISTANCE table. If resistance is not within specification, replace ignition coil.
If resistance is within specification, check resistance across terminals of the following distributor sensor. See DISTRIBUTOR SENSOR RESISTANCE table.
- Camshaft and crankshaft sensors. See Fig 1 and Fig 2.
If resistance is not within specification, replace camshaft sensor or crankshaft sensor on. If resistance is within specification, go to step 8).
Measure air gap of pick-up coils G1, G2 and NE. If air gap is within specification, go to next step. If air gap is not within specification, replace distributor.
Check for ignition signal circuit malfunction. See procedure for Code 14 (and Code 15 on SC400) in TESTS W/CODES article. If ignition signal circuit is okay, replace ignitor.

IGNITION COIL RESISTANCE

Application

Primary

Secondary

SC400

Cold ⁽¹⁾

.36-.55

9000-15,400

Hot ⁽²⁾

.45-.65

11,400-18,100

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

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

DISTRIBUTOR SENSOR ⁽¹⁾ RESISTANCE

Application

Ohms

SC400 (Camshaft & Crankshaft Sensors)

Cold ⁽²⁾

835-1400

Hot ⁽³⁾

1060-1645

⁽¹⁾	On SC400, the term "distributor sensor" refers to camshaft and crankshaft sensors. ECM controls ignition system based on signals from these sensors.

⁽²⁾	Sensor temperature of 14-122°F (-10-50°C).

⁽³⁾	Sensor temperature of 123-212°F (51-100°C).

Fig 1: Checking Right Camshaft Sensor Resistance (Left Is Similar)

Fig 2: Checking Crankshaft (Engine Speed) Sensor Resistance