i have an 89 d100 with a 3.9L that won't run and am getting at my wits end.
it'll run as long as the key is turned to start, so injectors and ignition are fine as soon as you let go to run, it just dies.
as long as you keep pouring fuel to it, it'll stay running, so the injectors are turning off. i've jumpered the asd relay in case it was shutting down, but it still does the same thing.
it has a different throttle body due to a fuel leak, a different computer, and a new ignition switch.
still the same problem. just lost as to why it starts fine then dies unless the key is in start, or you keep pouring fuel to it.
so, spark is not a problem.