Cranks but won't start?

My 73 has a extra little ground wire between the negative battery terminal and the radiater support. I had replaced that cable end ( terminal clamp ) with one of those poke the wires under a strap POS.
It was a poor patch job and would arch from time to time. After a long period of start, no start, flooded trying to start, I went to Advance auto and got a new ECU. Still no start. Walked away. Went back and properly repaired the negitive battery cable. Talked Advance into replacing a defetive ECU. Made sure to chassis ground it well before plugging in its connecter. No problem since. It's my theory that changes in technolgy over the years has caused many revisions inside those ECUs other than the 5th wire nolonger needed. Insufficient or intermittent ground will kill them. Good luck