Fuel pump wont run with key in on position,only when its cranking.

You're saying it will crank but won't turn over? Be aware that with the key in the 'on' position, the pump only runs for about 2 seconds until pressure is reached. Then it'll run while cranking as fuel line pressure drops since injectors are spraying fuel into intake manifold which causes fuel pressure to drop. If you suspect you are not getting fuel delivered to cylinders, check the fuel pressure regulator. It could be allowing fuel to return to tank and never pressurizing fuel supply line, so that injectors are firing blanks.

So, your saying that the vehicle/engine will start but then shuts off due to fuel pump not continuing to pump fuel? If so, check fuses & fuel pump relay to make sure it's all good. If all that is good, make sure you are getting power to the fuse & relay with key in on position.

You should always have power to both with key in on position, fuel pump relay has a diagram on it of how it works. If you are not getting power to either one with key on, then you can pull up the fuse/relay center under the hood and trace down the power wire. Make sure you know what you are doing, you ONLY want to identify the power wire that comes from the fuse and then jumps to the relay.

The relay turns power on & off to the fuel pump as directed by ignition switch, engine computer(PCM). You may need a wiring schematic of the fuel pump system to track down this issue. If the relay is not getting power from the fuse then you can cut the old wire, (dead leg it), but make sure you secure it! Then just simply jump from another power source, but ALWAYS install a fuse-able link! And, use the SAME size amp fuse as the manufacturer recommended/used! Make sure if you do this that the power source you use is only hot with key on! Hope this helps

You know that how?

What testing told you that?

I would only be guessing (that is all we do here)

But it sounds as though the ignition switch is worn
& effects the fuel pump circuit, when in the on position,maybe!

Get yourself a wiring diagram & see how the system should work,
then test it at different points that are accessible