yeah you need ot know for sure that youre getting signal to injectors or not, you will see flash pulses
TBI is a PITA when it gets old and starts developing problems, is usually never ending troubles past that point, component failures, wiring degradation, etc.
tbi fires from signal from distributor i know,
once i ran into problem with pink wire from coil over to distributor, it was busted inside insulation right near coil plug, wiggled it and would make injector spray fuel during crank, so got new wires from chevy for 20 bucks, white and pink ones,
but it could be anything in your case, anything from temp sensor to wires, to coil to who knows.