How Do You Test A Ford EDIS Ignition Coil?

The Ford EDIS (Electronic Distributor-less Ignition System) uses a set of coil packs to fire the spark plugs. Like the more traditional e-core and oil filled coils, this coil pack works on the principle of magnetic induction. Simply put, when a current is passed through the primary winding of the coil, a magnetic field develops around the coil. When the current is turned off, the magnetic field collapses and induces a high voltage spike into the secondary winding. This high voltage spike is the spark that fires the air fuel mixture by jumping the gap on the spark plug. Refer to the EDIS ignition system wiring diagram located in the service manual. Following that diagram, identify the power and ground wires for the individual coils in the coil pack. Test for power, at the coil's wiring harness connector, with the automotive circuit tester. Both the power and the ground wires should test positive for power with the key on and the engine not running. If power is not supplied to the coil, ...  more