I have a 2002 mercury mountaineer it will start if i put a screw driver to the starter it will start but when yo put the key in the ignition it won't start can tell me what wrong with it

Could you brake down your long paragraph ? Not sure what you have checked and what you need to check.

Please add more detail information as to your problem, what have you done as diagnosis, if any at all.

Its a possibility but I would think the fuel pump? That's where I would start. If it turns but doesn't crank then your most likely not getting gas.

Have you tested for a failed starter or it's solenoid ,
after it stops & you have nothing ?

Could be your loosing throttle position, if a sensor or
ignition coil is bad,that will shut it down

Check for OBD Codes

Starter solenoid or neutral safety switch or bad key switch or broken wire or bad connection.

Is the battery good in it?

I'm going to first assume that you've checked the battery terminals for gunk build-up. If the electrical system is OK, then the problem likely lies in the gas delivery. You might want to check out the starter anyway. Also, replace the fuel filter and put some Sea Foam or equivalent carb/electric ignition jet cleaner in the gas tank. I might add that your car is 17 years old. Start looking. . .

Your ignition starter is bad.

when it won't crank you will need to start at the battery and work your way to the starter checking for voltage
battery - cables - ignition switch - neutral safety switch - starter

try checking the starter relay

Sounds like the battery is dead, you have just enough power to have the lights come on, but no cranking of the starter. Try putting the battery on a trickle charger, or hook up jumper cables to another car which is running. Let it run with the jumper cables connected for two mintues before you try and start your car.