The secondary ignition check tests for faulty spark plugs, plug wires, or IC Module/Coils. This test requires the J 26792 (or equivalent) spark tester (ST-125).
Ensure that a good DVM contact is made when measuring spark plug resistance. When manufactured, the normal resistance for he spark plug is 900-2500 ohms but resistance growth up to 10K ohms is considered normal.
- The spark tester presents a more difficult load on the secondary ignition than a normal spark plug. If a miss, stumble, or hesitation is being caused by a spark plug not firing, the spark tester should also not fire.
- Check the suspected spark plug wire resistance to ground and resistance end to end. If the wire is shorted to ground or measures more than 15k ohms, replace the wire and retest.
- Remove the suspected spark plug and perform a physical inspection. Look for cracks, chips, splits, or other abnormalities. If any occur, replace the plug. Measure the resistance; if out of spec, replace the plug.
- If the no spark condition follows the suspected coil, that coil is faulty. This test could also be performed by substituting a known good coil for the one causing the no spark condition. Otherwise, the ignition module is the cause of the no spark condition.
- For diagnosis of the ignition system components on the 4.6L engine, refer to the following diagnostic charts. Use of special tools for the test procedures listed may be required. The tool numbers will be given, when applicable.