answer:Electrical issues are always a bugger to track down, especially on a car. Take this from a former Navy electrician who has owned many a beater car. Most electrical issues involve grounding issues. Is the engine block properly grounded to the frame? If not then you will have issues as the block itself is part of the electrical circuit for your spark plugs. Is it possible that your replacement alternator is bad? Without a good alternator, your car will only run until the battery is dead, which takes no more than a few minutes, and a bad alternator will destroy a new battery in short order. Aside from that, the only other things I can think of involve using a multimeter and testing everything hither and yon, a task onerous enough that I would sell a kidney (preferably somebody else’s though) to pay a mechanic to do it for me. I had one car that had issues because the kid who owned it before me miswired the stereo in such a way to render the taillights utterly inoperative, so your gremlin may be somewhere other than the engine compartment.