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I have a 90 F150 with a rebuilt 302, with a duraspark II dist which I originally operated with a GM HEI module. The truck began to lose spark when starting on an intermittent basis, but when running it never quit. I replaced the coil which seemed to help for a time and also replaced many modules as well as coil wires and everything seemed the help for a while. I then replaced the hei module with a Mallory VIa box and replaced the pickup inside the dist. and the coil again, it ran with no failures to start for a few days and is at it again. When it has no spark there is power to the module and coil. Any ideas would be appreciated as I've replaced about all the ignition system, and still never know when I'll have spark when starting.