It may seem to not have a distinctive on/off because it happens fast enough that the filament of the test light doesn't stop glowing before it's back under power. Wavering means that the primary control is trying to make and break the ground to the coil. To be positive that we aren't barking up the wrong tree, I would put a known good spark plug on the end of one of the plug wires, ground it to the engine and see if it fires when cranked over. If it fires then you don't have an ignition problem. If there is no spark, leave the key on and touch a grounded test light repeatedly to the negative post on the coil that goes to your "test" spark plug. If the coil is good, it should fire the plug every time you touch it. I would anticipate that the coil is ok, as there are three of them and,while nothing is impossible, the likelihood of all three of them being bad is slim to none. That time delay module that you are talking about controls the positive side of the coils and you have seen that the coils have power when it won't start, so that module has been ruled out. I think I'll stop there until we confirm whether it is an electrical or a fuel problem. If it continues to be electrical I'm thinking either the transistor module or it's ground supply. To be continued!