The distributor in the Ford Mustang triggers the ignition coil and then transmits the energy (spark) produced by the coil to the spark plugs at the proper time to ignite the compressed air/fuel mixture in the cylinders. Common failures of the Mustang's distributor include failure to trigger the coil, failure to trigger fuel injectors, failure to control the timing of the spark and failure to transmit the spark to the spark plug. Diagnosing these problems is a straightforward process of elimination through testing the possible causes of the failure.
Things You'll Need
- Ignition spark tester
- Automotive circuit tester
- Timing light
- Injector test light (Noid light)
Remove a spark plug wire from a spark plug using a spark plug wire pliers to twist and pull the wire's boot until it unsnaps from the spark plug. Insert the terminal end of the spark tester into the plug wire and clip the ground wire of the tester to the engine block.
Have a helper try to start the engine while you observe the tester. Repeat this test for several spark plug wires. If a strong spark is present at most of the spark plug wires replace the wires. If no spark is present at any of the plug wires go to the next step.
Unplug the coil wire from the distributor cap. Attach the spark tester to the coil wire and engine block in the same manner as before. Have a helper again try to start the engine while you observe the spark tester. If spark is present at the tester replace the distributor cap and ignition rotor. If no spark is present go to the next step.
Unplug the coil wire from the ignition coil. Attach a test light to the engine block and hold the probe end of the test light within a 1/4-inch of the coil terminal. Have a helper try to start the engine while you observe the gap between the test light and coil terminal. If a bright, strong spark is present replace the coil wire. If no spark is present go to the next step.
Unplug the coil's electrical connector. Turn the ignition key to the run position and touch the probe end of the test light to the terminals in the electrical connector. One should light the test light indicating power is being supplied to the coil. If neither terminal lights the test light replace the ignition fuse. If power is supplied go to the next step.
Move the test light's clip from the engine block to the positive battery terminal. Touch the test light to the terminal in the electrical connector that did not light the test light. Have a helper try to start the engine while you observe the light. It should flash. If it does not flash replace the pick-up coil and ignition module in the distributor.
Timing and fuel injector control
Unplug the electrical connector from one of the fuel injectors. Insert the noid light into the electrical connector and have a helper try to start the engine. If the light does not flash replace the distributor's pick-up coil and ignition module.
Clamp the battery cables of the timing light to the battery and clip the pick-up of the timing light to the number one spark plug wire. The number of plug wire is the front wire on the passenger-side of the engine in the Ford V-6 and V-8, and the front wire on the L-4, engines.
Start the engine and aim the timing light at the timing marks on the harmonic balancer located behind the crankshaft pulley. Observe the timing marks as you open the throttle quickly. The timing marks should move indicating the distributor is advancing the timing in response to the throttle. If the timing doesn't move replace the distributor's ignition module and pick-up coil.
Tips & Warnings
- Wear safety glasses and work gloves when working around a running engine to prevent serious injuries.
- "Chilton 1994-98 Ford Mustang Repair Manual"; George B. Heinrich III, ASE, SAE; 1997
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