Possibly someone hooked up a test wire to the fuel pump.
Looks more as though a factory installed wire.
So the wire is coming out of a wrapped wiring harness?
The first thing I’d do is stop by the local GM dealer and request a schematic AND a wiring diagram (different drawings) for the fuel system wiring from the parts window guy. If you ask nicely and he’s a decent guy he should be willing to print those for you. Use those to try to figure out where that wire goes. A live wire dangling by the fuel tank should not be hard to identify.
It could be coming from (or going to) the inertial cutoff switch, one of the sensors, or who knows what else.
Well, now we’re onto something!
It should be very easy to find the other end of that wire; where it used to connect. That is just a matter of looking around…which may not be so easy if that means getting between the tank and the car (dropping the gas tank), but in any case a little detective work should find the issue…and that is probably the issue that you were having that precipitated this post. 
If the computer loses the signal from crankshaft position sensor and thinks the crankshaft isn’t rotating, the computer see’s no reason to operate the fuel and ignition systems. Including the fuel pump.
The OP described the engine shutting off as if someone turned the ignition off.
I still say it’s the crank sensor.
Tester
Same exact issues. I believe it may be electrical. I replaced fuel pump also.