1993 Ford F150 - No Spark - Finally SOLVED (bad coil)
I had intermittent problems starting for several months (usually when it was humid or raining). Finally, after replacing the rotor/cap/wires/plugs, it stopped having any spark at all and wouldn't fire.
After reading these forum results, I first tried replacing the ignition control module on the left front panel ($50). That didn't make any difference. Next, I tested the resistance for primary and secondary poles on the coil. For my TFI-IV model, the specs call for a range of 8,000 to 11,500 ohms on the secondary poles. (measure between the main spark plug connector on the coil and a ground). My reading was 7,410 ohms... just barely below the acceptable range. Though doubtful, I replaced the coil anyhow ($20), and VOILE! It started and ran perfectly!
I hope this helps someone else. My advice is to replace the coil first since it's cheaper. Both the coil and the ignition control module are easily accessible (though the ignition control module requires a special tool to reach the bolts holding it to the heat sink)