91 s10 blazer died on road on way to work

my 91 S10 blazer 4x4 just stopped running the other morning--had to walk home--get tow truck. Too cold and windy to try diagnosing it out there. After bringing it home did diagnostics (today as the weather warmed up) as found in the Haynes manual and found them to be useless. Anyway fuel system OK. Found that there was no spark. After alot of fumbling replacing the module etc, I thought that the coil was suspicious as it did not produce a spark when I tried to switch it on and off manually. Walked to AutoZone and got new coil, replaced it, hooked everything back up, and presto! started right up.-----Speaking of manuals, I wonder if someday one will be written that actually is useful and makes sense. A manual should explain the function of a system, and then show ways of testing it without taking the most complicated ways of doing it. For example, Haynes has a page on doing an ohmeter check on the coil. Well, that would apply only if it were shorted or open-circuit! Obviously coils can do strange things (like not work) when the high voltage load is ramping up in there.