MOTORCRAFT DURA-Spark II Ignition Systems: Testing: Notes
CAUTION:
When checking the secondary voltage, do not remove the following spark plug wires while the engine is running or cranking:
Plug No. 1 or 8 on V8 engines.
Plug No. 3 or 5 on 6 Cylinder engines.
Plug No. 1 or 3 on 4 Cylinder engines.
Perform the following tests using an oscilloscope which has inductive type clamps. Always follow the scope manufacturer's instructions. Also use suitable grounding probes and insulated pliers where necessary.
NOTE:
On vehicles with a catalytic converter, do not run engine for more than 30 seconds with a spark plug wire removed.