My girlfriends truck will start just fine and idle fine but after a few minutes of driving the engine will just cut out suddenly and she is forced to coast it to the shoulder. It was running fine till about three days ago when the starter went out. So we replaced the starter. Then the truck would turn over but wouldn't start, so we replaced the spark plug wires and the distributor cap, rotor and the sensor or sending unit below the rotor. (Little black unit with two male connections on each end). No it won't start at all. And I am not a gasser engine guy. I know the basic rule; fuel, air and spark. I am guessing that it's not getting spark.

 

Well first things first, not sure by your post but you say it is not running now? or it runs and dies after short drive? The part under the ign cap is the ignition module. Best approach to this is to see if it intact does not have spark, no point in guessing. If you find no spark then check (without unplugging it) the power on the red(i think it was red) wire at the distributor cap. with key on you should have 10-13 volts. If you do not have 10-13 then you may have a supply voltage problem, those trucks all had power supplied to the ignition through fusible links at the starter.(fires that act like a fuse and will burn out. Try a jumper wire from the battery positive post to the re wire on the back of the alternator, the one with the stud and nut at the back of alternator. If the vehicle continues to run that way then you have a fuse able link burnt or not connected properly at starter.