Ignition Switch: Testing and Inspection

Fig. 1 Lucas twin coil ignition system:

These models are equipped with a Lucas twin-coil constant energy ignition system. The main coil primary winding is connected in parallel with the primary winding of the auxiliary coil. The high tension post of the auxiliary coil is not used and therefore the outlet is sealed. The secondary coil is used as a large inductor and enables the ignition system to achieve required performance at high engine speeds under load.

Test 1

1. Load test battery. Check the specific gravity of each cell. A variation of 0.040 in any cell means the battery is suspect. If the battery is not sufficiently charged, charge or replace as needed before proceeding with the following steps.
2. Remove the coil wire from the center of the distributor cap and hold the end of the lead approximately 0.25 in. (6mm) from a good ground. Crank the engine and check for spark. If a spark is obtained, reconnect the coil wire and check the spark plug wires, spark plugs, distributor cap and rotor.

Test 2

1. Switch ignition on and check voltage at main terminal of coil C.
2. The main coil voltage should be 12 volts. If voltage is below 11 volts, check wiring from ignition switch G.

Test 3

1. Disconnect lead from negative terminal of main coil and switch ignition on.
2. Negative terminal voltage should be 12 volts. If voltage is zero, replace main coil. If voltage is 12 volts, repeat Test 1 and Test 2 on auxiliary coil D.

Fig. 2 Distributor Exploded View:

Test 4

1. Disconnect distributor leads from control module B.
2. Measure resistance of distributor pickup. Resistance should be 2.2 - 4.8 ohms. If reading is not 2.2 - 4.8 ohms, replace distributor pickup.



Test 5

1. Connect voltmeter between positive terminal of battery and negative terminal of main coil and switch ignition on.
2. Voltmeter should indicate a zero reading, crank engine and voltmeter reading should rise to between 2 and 3 volts. If voltmeter remains at zero, control module may be faulty.