Key turns to "start" position. Nothing happens, key doesn't spring back to "run".

Sounds like a bad spring in the ignition cylinder or the ignition switch itself isn't returning the key and switch to the Run position as it should. Most any auto repair facility can check and replace the switch for you. Note that the ignition lock cylinder (where you put the key in and turn) is NOT the switch. The switch is connected by a linkage up to the lock cylinder. The cylinder moved the linkage and the linkage moves the switch.

It would not hurt to squirt some WD-40 or other spray lubricant in the lock cylinder to see if that resolves the problem. Don't use lithium grease though, only use a light lubricating oil spray, and don't go crazy with it. Just a couple of squirts.

First turn of the key energize the car electrical circuits for some circuits radio ets. 2nd turn of the key energize the the starting cycle, when you turn the key to the third spring loaded start mode it completes the circuit to the starter solenoid which engages the starter and start the car, the spring in ignition return the key to ignition on.
Maybe you have a malfunction in the ignition on position. Dont have a large bunch of keys hanging in your ignition, it sings back and forth when the car is in the start mode and cause havoc to your ignition switch.

Ignition switch....the electrical ignition switch. To verify, find the thick white wire in the harness coming from the switch and do two things; first, check for power at this wire, when you switch the key position to start. If nothing, power the wire momentarily with the key in the run position, and your car should start.

To clarify something you said, the accessories should go off when the key switch is in the start position.
Are you getting power to the coil and the computer when the key switch is on and in start ?

Take a test light to the small wire on the starter and have someone turn it to the start position. If the light lights up and the engine doesn't turn over, I would suspect the starter itself. If the test light doesn't light, try it in neutral and repeat test. If it still doesn't light up, it may be the PRNDL switch or the ignition switch itself.

he ignition switch generally has four positions: off, accessories, on, and start. Some cars have two off positions, off and lock; one turns off the car, and the other allows the key to be removed from the ignition. When the key is turned to the accessories position, certain accessories, such as the radio, are powered; however, accessories that use too much battery power, such as window motors, remain off in order to prevent the car's battery from being drained. The accessories position uses the least amount of battery power when the engine is not running, which is why drive-in movie theaters recommend that the car be left in theaccessories mode during the movie.

The on position turns on all of the car's systems, including systems such as the fuel pump, because this is the position the ignition switch remains in while the car's engine is running. The start position is spring loaded so that the ignition switch will not remain there when the key is released. When the key is inserted into the ignition switch lock cylinder and turned to the start position, the starter engages; when the key is released, it returns to the on position, cutting power to the starter. This is because the engine runs at speeds that the starter cannot match, meaning that the starter gear must be retracted once the engine is running on its own.

Either the ignition switch or the lock cylinder may fail in a car, but both circumstances have very different symptoms. When the ignition switch fails, generally the electrical wiring or the plastic housing develops problems. The car may not turn on and/or start when this happens. Also, the spring-loaded start position could malfunction, in which case the starter will not engage unless the key is manually turned back to the on position.

When the lock cylinder malfunctions, however, the operation of the key itself will become problematic. If the tumblers become stripped, the lock cylinder may be able to turn with any key, or you may be able to remove the key when the car is on. If the tumblers begin to shift, the lock cylinder may not turn. Sometimes the key can be wiggled until the lock cylinder turns, but it is important to remember that this is only a temporary fix.

Replacing an ignition switch can be tricky business, particularly in newer cars, because of the anti-theft devices used in cars. Once the ignition switch is separated from the back of the lock cylinder, the car can be started with a screwdriver, making it vital that this switch be difficult to get to. It is important to consult a shop manual before attempting this kind of repair, as the anti-theft devices may require special tools; attempting to remove an ignition switch without the proper tools can render the car inoperable.

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The first step is to narrow down the cause of the no-start.

Let's go over the process of starting the car, so you have a better understanding of what is going on when you turn the key:

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The first step is to narrow down the cause of the no-start.

Let's go over the process of starting the car, so you have a better understanding of what is going on when you turn the key:

Here is what happens on a properly running car:

• You sit behind the wheel and insert the ignition key into the switch.
  

• You then turn the key to the spring loaded start position. When you do that, the ignition switch engages the starter by connecting the battery to the electric starter motor which, in turn cranks the engine over. This can be easily heard and is referred to as cranking the engine over.
  

• The next thing you will hear is the engine running, which is your signal to release the key.
  

• At that point, the engine is running and you are ready to place the transmission selector in Drive and be on your way.
  

ere is what happens on a properly running car:

• You sit behind the wheel and insert the ignition key into the switch.
  

• You then turn the key to the spring loaded start position. When you do that, the ignition switch engages the starter by connecting the battery to the electric starter motor which, in turn cranks the engine over. This can be easily heard and is referred to as cranking the engine over.
  

• The next thing you will hear is the engine running, which is your signal to release the key.
  

• At that point, the engine is running and you are ready to place the transmission selector in Drive and be on your way.
  

I take it the key fob doesn't work Try disconnecting the battery for 30 minutes and see if that will reset the alarm. You may need the key fob to reset.

It sounds like your ignition key isn't returning all the way back from the start position to the run position because the return spring has gotten weak. The next time it happens try turning the key back to the run position.

On the back of the ignition switch is a plastic casing which retains a spring to return your key to the correct position once the car has started. The plastci casing wears and the spring does not work sufficiently. You need to replace the ignition switch casing/back end.