Kill switch? Stopped got Gas turned car off, will not start. Have power but does nothing no crank

Typically the only time that the fuel pump loses power is in the result of an accident to prevent a fire. If your car just died and would not turn over today sounds like you may have had your alternator go out; therefore running on your battery until it is drained. No warning lights on the dash or did you notice the ammeter guage discharging by chance?

If your fuel pump is in the gas tank the fuel pump is cooled and lubricated by the gas. If you run out of gas and keep trying to start it many times you can damage the fuel pump. If you have a older car you can try putting a little gas in the carburetor and see if it cranks, if it cranks with gas in carburetor you know it is a lack of fuel problem. You might try spraying starting fluid in air filter but to much can damage your engine. Some links below may provide some help.
https://www.yourmechanic.com/question/car-won-t-start-after-it-ran-out-of-gas-and-was-filled-again
https://www.bimmerforums.com/forum/showthread.php?1881026-Ran-out-of-fuel-now-won-t-start-please-help!
Your vehicle fuel pump can run and pump gas but depending on your vehicle you may not have enough fuel pressure to run. I would check your fuel pump fuse and relay and fuel inertia switch/fuel pump kill switch if you have one. I do not know why running out of gas would cause them to fail but it is something to check.

Doesnt turn on as in theres no power? Cranks but doesnt start? Has power but doesnt crank?
You also need to provide details about what automobile this is. Could be a bad battery, blown fuse, bad sensor, etc.

If you replaced the ECM and didn't reprogram it. There's your problem. The ECM doesn't recognize the security code. And it will start and kill the vehicle three times before shutting down everything. IE.. starter, fuel.

If the engine does not crank, I doubt it has anything to do with the fuel system. You would need to find out if you have power at the starter posts when the key is in start position. Will it crank in neutral, and is the security light flashing ?

Sounds like you may have possibly TWO problems here. The ignition key not turning past the run position or even to the run position is most likely a lock cylinder issue and may be fixed by replacing the ignition lock cylinder, As for the power being killed when turning the ignition to the start position, that sounds like a defective ignition switch. these items are two seperate parts. The reason for the turn signal issue may be related to the ignition switch fault.
Hope this helps.

The first thing to do is to check for power at the starter, the big wire should have power at all times then have someone turn the key and hold it in the crank postion and test for power at the small connection at the starter if theres power then you have a bad starter, if theres no power then check the ignition swith and the wiring to in and see if it throws power in the crank spot and last if that checks out check the neutral safety switch, make sure power is flowing through that in park or neutral.

buy some brake clean. spray a little in throttle body. if it starts and stalls you need a fuel pump or you lost power to the fuel pump. If nothing changes you may have a bad crank sensor or ignition issue.

You have a fuel reset switch that needs to be pushed back in. This is why you are not getting any thing to happen

The fuel pump inertia switch is located in your right front passenger
area. It is located on the right side of the transmission hump on the
toe board, just under the edge of the carpet. If you don't see any gas
leaking, or smell any gas, push the button down that has popped up
on the top of the switch. This will allow power to go to your fuel pump.

sounds like a crank sensor.
The crank sensor is usually mounted at the seam between the engine and the transmission. It has three wires: one will have 8V on it compared to ground when the ignition is ON, and if you measure the voltage between the other two wires you should see ii switch back and forth between 5V and 0.3V as you turn the engine by hand using a socket on the crankshaft bolt, again this is with the ignition ON. If you don't get that then the sensor is bad. You can read these voltages by using a very fine pin pushed thru the insulation of the wires to make contact with the conductor inside.