Puff of smoke and no spark
 

This is my first ever forum experience (yay!) I'm helping a friend with '94 f350 uhaul truck. Was running fine. Puff of smoke from under steering column. Ignition on and constant 'clicking' in distributor. Pulled coil wire off and spark jumping steadily without engine turning over. He's replaced ing switch, ig module, distributor with sensor, and coil. No spark from coil at all. I've tested the 3 fusible links inside at firewall with ohm meter and have continuity but there is no voltage when checked with 12v test light. I'm lost and he's just been throwing parts at it. I'm not a certified mechanic but can find my way around so be gentle...Thanks in advance. ps: I couldn't find anything searching on the forum and if I missed a thread please direct me.