If you can live with two SPDT momentary pushbutton switches (one ON, one OFF), this would be a simple implementation. Each switch would supply a momentary pulse with one switch setting the relay and the other switch resetting it. It is basically a pushbutton H-Bridge.

I just read the original post again and realized you want REMOTE operation. Wouldn't the simplest fix be to tie the fuel pump supply into the ignition circuit of the car?

 

Talking about a latch that controls a latch
Heres my way of doing it:
View attachment 183643
Assuming your pulse is 12V
This circuit remembers the state and switch it automatically.
How it works:
It centered around a D-Flip Flop, the input pulse triggers the flip flop, the flip flop then trigger a 'one shot' pulse to turn on/off the relay oppose to the previous set state

Edit: Note: LEDs resistors need to be calculated. I forgot to change them

Hi iimagine, I am going to attempt to build this circuit in post #12 but I have a few questions.
1. What do the circle electrical symbols represent?
2. Where does my power in/out for my fuel pump tap into the circuit?
3. Where does my negative 200mA trigger wire tap into?

 

Try getting a different latching relay.