2000 impala wont crank

You need to test the start wire at the starter when the key is turned to crank position to make sure it has power during cranking. Sometimes tapping on the starter motor with a hammer while cranking will engage a bad starter motor

Either starter or starter relay, check the relay first.

do you hear a click if you do its probably your starter cylinoyed if it works when you jump the wire you are bypassing it hope this helps pat

How about the starter.

you have a shorted battery (have it tested) or there is a loose connection. A starter motor pulls a large amount of current when it engages, a loose conection or shorted battery will all the voltage away from the dash,lights etc.

Check power to starter motor solenoid, solenoid operation and starter motor voltage during cranking. If the starter motor is receiving power from the solenoid, but isn't cranking, then replace the starter motor.

Also check the condition of battery terminals, wiring and connections. Also check the earth wire from the body to the engine.

first i would recheck all conections and make sure all on right even on the starter senoid / and on most cars thier is a starter relay and fuse wich should be in the fuse panel box under the hood should have some very large maxi fuses and smaller ones starter fuse should be a maxi fuse which is the larger ones if u have the owners manual for this car it will help locate this fuse quicker good luck

Does the starter kick out and spin normally out of the car? Have you checked the condition of the flywheel? Ususally the starter doesnt turn until the solenoid kicks the gear out to engage the flywheel. Check if the gear on the starter is bad, it should slip one way, and not the other.

I assume your motor crankshaft is not 'seized' or otherwise locked up.

Check your battery terminals are clean and firmly attached,
Check battery ground connection is securely connected to the chassis and the motor/chassis ground connection is intact.
Check for 'click' sound as starter solenoid is engaged when Ignition sw set to 'start' position.
If no noise from starter motor, and +12v applied to the starter engage solenoid terminal, then the starter motor may be faulty.

It's not your starter or battery it sounds like a fuel problem to me, check and see if your fuel pump is working alright or not it seems to me that your engine is vapor locking every time your get your engine up to temp. and turn it off it's vapor locking your fuel system have your fuel pump and complete system checked out.