I just replaced a two prong outlet in the bathroom with a new Leviton GFCI. When I turned the power on, the outlet was not on. I pushed the reset button and then I saw a bit of a flash from the outlet and the circuit breaker tripped.
I have very old wiring- the kind that is fabric insulated. The box tested that it was grounded with my little voltage indicator with the little light on it, but I didn't connect a ground wire yet. All I did was connect the hot wire to the brass side of the line and the neutral wire to the silver line side. Nothing else was done.
I then put the old two prong outlet back on and it appears to be working as normal again.
What could have caused this pop and flash from the GFCI outlet when I pushed the reset button for the first time? Did I install it incorrectly or is there something else going on?