Late model Fords are equipped with coil packs rather that the old style individual coils for each cylinder. These coil packs are solid state units that transmit electricity from the Ford's computer control module to the ignition wires and then to the spark plugs, allowing them to fire in a precise order. Coil packs are fairly simple to diagnose with these few easy steps.
- Skill level:
- Moderately Easy
Things you need
- Digital volt ohm meter
- Electrical contact grease
Start the vehicle and note the running condition of the cylinders. Is the engine running smoothly or is the engine missing on one or more cylinders?
Locate the coil pack for your Ford. They are usually located near the right bumper well.
Check that each plug wire is firmly plugged into the coil pack and in the right order. The number of each wire is stamped next to the connection terminal.
Inspect each wire connection for discolouration or damaged wires.
Use your volt ohm meter to check wire continuity by touching the ground lead to a suitable ground lead and using the red probe lead to check for an ohm reading. Ohm readings should be 1.5V for primary wire inputs and 8,000 to 9,000 for secondary wires. Infinite ohms reading (the meter will have a zero reading) indicates an open circuit somewhere in the wire harness that will need to be located to its source and the wire replaced.
Replace the coil pack if all recommended steps have been taken, everything checks out properly yet the spark plugs are still not firing correctly.
Tips and warnings
- Visual inspection should tell you everything you need to know for this procedure. Solid state ignitions do not have moving parts that can be repaired or replaced. The coil is replaced as a unit.
- The ignition system generates extremely high voltage that can damage test equipment and harm the technician. Be sure to follow the steps, as outlined, to prevent any problems.