Notes On Fault Tree
NOTE:
Numbers in list refer to circled numbers in diagnostic flow chart.
- After performing the power balance test, if one cylinder or non-companion cylinders had no RPM change, see Fig 1 . If 2 companion cylinders had no RPM change, see Fig 2 . Otherwise, see Fig 3 .
- The J 26792 spark tester (ST-125) 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.
- The companion spark plug shares the same ignition coil with the spark plug being tested (1-4, 2-5, 6-7, 3-8).
- A suspected ignition system 'miss' may actually be a fuel system problem. Perform FUEL & AIR CONTROL SYSTEM DIAGNOSIS CHART 6C-1: FUEL SYSTEM CHECK in SELF-DIAGNOSTICS -- ALLANTE article, if it has not yet been performed.
- If the no spark condition follows the suspected coil, that coil is faulty. Otherwise, the ignition module is the cause of no spark. This test could also be performed by substituting a known good coil for the one causing the no spark condition.
- 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.