Electric fuel pump and mechanical ?
Not sure, but I believe the original question was if you could run both. I don't think that's a good idea. The electric can produce enough pressure to damage the diaphragm in the mechanical pump. So it's one or the other.
As for "knocking the wire off" I suggest using areospace logic on crucial items like that: Create the best connection you can and protect it from damage. Triple overkill on something is good if you don't want to be fixing it on the road, which usually happens at night, in the rain, and when it's COLD out.