4 pin ECU/2 terminal ballast or 5 pin ECU/4 terminal (dual) ballast? Pull the yellow "ign" wire off of the starter relay to disable the starter to save the battery/elim the noise distraction & have a helper hold the key to "start" & you see if the coil positive pri terminal and the ECU main feed terminal (2 terminals on a 5 pin ECU) are getting fire. Pull/clean the bulkhead & work back toward the ign sw or downstream forward to find the open

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