I know this is probably a very common.

Hi, I know this is probably a very common question but I can find no answer anywhere else.
My clio would not start. Ok not a problem, I check underneath the bonnet for causes (bearing in mind this is completely random, no unordinary use, no previous problems etc) I notice a black rattling box, which after scouring the internet I find is a common problem and I take the lid off to inspect. It has chafed through insulation of two wires. I insulated the wires, tried the car, no joy. A bump start gets the engine running, but dies, even with constant throttle. I got jump leads and started, it ran but judders between 5-15k revs. Ok better than nothing. I left it, and a cup of tea later, it wouldn't start. I unplugged the clips the black box was covering to look, cleaned them a bit and noticed one tiny broken pin. Surely this can't be the cause of all the trouble? Can't cause the car to not start? I gather its something to do with fuel intake though, which I guess makes sense, but one pin? Maybe this black box is completely irrelevant, I dont know. I'm stumped.