A problem with the ignition system can result in an engine that will not start or an engine that starts but runs roughly. Troubleshooting the cause of an ignition problem requires an inspection of each of the system's main components, including the battery, the spark plugs and wires, and the distributor. Fortunately, because the ignition system's is fairly basic in design, the cause of most ignition problems can usually be located quickly.
Check the condition of the battery with a voltmeter gauge. Place the black probe to the negative battery terminal, and then place the red probe to the positive terminal. The voltmeter should show between 12 and 14 volts. If it does not, have the battery and alternator inspected by a professional.
Examine the entire length of each spark plug wire for cracked or burnt insulation.
Examine the length of the spark plug wires for crossfire potential. Crossfire occurs when the current from one spark plug wire interferes with the current from another spark plug wire. Crossfire typically occurs when two spark plugs wires touch. To avoid this possibility, Ford installed spark plug wire separators, which are plastic brackets that hold the wires apart. The separators are located on top of the valve cover(s). If a wire has slipped out of its separator, press the wire into its groove within the separator.
Remove the spark plugs with a spark plug socket wrench and examine each plug's porcelain tip. If the deposits on the tip are anything but a light brown color, replace the plugs.
Examine the underside of the distributor cap for black or green-colored metal contacts, which could be preventing the spark from reaching the spark plugs.
Examine the metal tip of the distributor rotor for a burnt tip, which could be preventing the spark from reaching the distributor cap.
Check the distributor point gap with a blade-style feeler gauge. The points are the components at the base of the inside of the distributor, underneath the distributor cap, that look like tweezers. The distance between the two tips of the points is the gap. The gap must meet the engine's specifications. Consult the engine's specification's manual to determine the proper gap, as the gap varies depending on the year of the Mustang and the type of engine.
