OPUS Ignition Test Procedure
1978 XJ6, 12, XJS

The following is the factory recommended procedure for diagnosing ignition system faults in the above care, all models. For the corresponding system schematic diagram see the accompanying  figure.
 

1. Check battery:

The specific gravity reading should be between 1.260 and 1.268.

2. Check H-T spark:

a) Remove the main H-T lead and insert known, good test H-T lead into coil chimney. With insulated pliers, hold the free end approximately 1 /4" away from the engine block.

b) With the ignition on, crank engine. Regular sparking should occur. If sparking occurs, check the distributor cover for signs of tracking etc. Check H-T leads rotor arm insulation, spark plugs, coil chimney, fuel supply.

3. No Sparking-Amplified Check:

a) With test H-T lead in coil chimney and with free end approximately 1/4" from engine block, switch on ignition and remove white-blue lead from drive resistor. A spark should occur each time white-blue lead is removed.Replace white-blue lead after test.

b) If sparking occurs, check pick-up air gap which should be 0.014 inches to 0.016 inches, and check that the distributor shaft rotates. If correct, replace module.

4. Voltage Supply:

Remove distributor cover and insure that no ferrite rod is in the vicinity of the pick-up module. With ignition on, connect volt meter lead, negative to ground point, and positive lead to input of ballast resistor. The reading in each case should be at least 11 volts. If less than 11 volts, check wiring for excessive resistance between battery and checking point.

Voltage at positive terminal coil ballasted should be 4 to 8 volts. A low voltage reading indicates excessive resistance between the checking point and the bttery and high reading indicates the ballast resistor has been by-passed or the coil or amplifier is faulty. Continue the test.

5. Voltage at Coil Negative:

Disconnect negative lead. Connect volt meter negative lead to ground, positive lead to coil negative terminal. Volt meter should read battery voltage. A zero reading indicates faulty coil. Reconnect coil negative lead to coil with volt meter still connected as in prevous check. Reading should fall less than 2.5 volts. If reading is higher than 2.5 volts, check resistance
value of drive resistor. It should be 9 to 11 ohms. If drive resistor value is correct, replace electronic module.

6. Switch Check:

Leave volt meter connected as in previous check and crank engine. Volt meter reading should fluctuate between 2 to 4 volts, approximately, dependent on cranking speed. If volt meter reading remains steady, no fluctuation, replace electronic module. If results from check no. 2 is no sparking, replace coil.

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