Ignition won't power Starter to crank. It started out with slight delay on firing starter when turning key. Now NO response to turning key. Ignition or Starter??

It sounds like there may be an issue with the ignition system on your 2005 Pontiac Sunfire. Here are a few potential causes for the problem you're experiencing:

1. Faulty ignition switch: The ignition switch is responsible for sending power to the starter, so if it's not working properly, the engine may not crank.
2. Bad starter solenoid: The starter solenoid is responsible for engaging the starter when you turn the key, if it is not functioning properly, the engine will not crank.
3. Wiring problem: If there is a problem with the wiring leading to the starter or ignition switch, it can prevent the engine from cranking.
4. Failed crankshaft position sensor: This sensor is responsible for relaying the engine's position to the car's computer. A bad sensor can cause a no-start condition.
5. Failed PCM (Powertrain Control Module) that can prevent the engine from starting.

It's likely that one of these issues is causing the problem you're experiencing, but it can be difficult to diagnose without proper testing. It would be best to take it to a professional mechanic for proper diagnosis and repair.

Could have faulty starter relay that provides crank signal voltage to starter when key is turned to start. Assume the no voltage to plugs or fuel pump performed when jumping the starter directly at the starter. Was the key turned to run position? Needs to be or no power to rest of system.

Concentrate on the starting circuit: from the ignition switch to the neutral safety switch to the starter relay to the starter solenoid on the starter. If it won't crank, one of these parts or the wiring associated is not working right. Quite often the electrical contacts in the starter solenoid become pitted, slightly burned maybe, and lose contact. If you have power on the solenoid wire when key is held in crank and starter won't operate, the solenoid is the problem.

If you have power in aux position(ex.)radio works but doesn't when you put the key in the start position,the ignition switch is bad,the contacts are warn out for starting/cranking&run positions,these are used everytime you start your car,but auxillary is ony used once in awhile(ex.)your sitting listening to music while waiting for someone to come,but if you do have radio in the run position,but no cranking/starting you could have a blown resistor on fire wall or fuse for ignition,or the starter has called it quits,good luck I don't know if the starter is clicking rapid or just one click or just no power not cranking or cranking a better description of everything that happens will make this alot easier

No, it isn't an ignition issue.

Check power to the starter motor solenoid.
If this is getting power when cranking, then the issue is with the starter motor solenoid or starter motor. Replace.

many things will cause no start problems could have faulty ignition switch.use test light see if power going to starter if not check ignition fuse to starter.if power going to starter, more likely starter solenoid or starter faulty.if ignition fuse okay and starter and solenoid okay still no start problem could be in the ignition switch or inhibitor switch faulty.code scan for faulty theft security system which will also cause no start conditions.

Sounds like your key is no longer actuating the starter/not matched to the vehicle key code, if you can turn it on but no cranking action is done when trying to start.

You may be right. Sometimes a starter test doesn't reveal everything. But before you pull the starter, do this quick test. It should confirm if problem is the starter or the ignition switch. When the car won't crank over, pull the small wire off the starter solenoid (on the starter), and check if it has power when key is held in crank position. You need a helper to hold the key in crank. If the wire has power (use a testlight or meter to check for power), and the starter won't crank, pull the starter off for testing or replacement. But if there is no power on the wire when key is held in crank, then it confirms that power is not being transmitted from the switch to the starter. Not to say for sure it is the switch, could also be another part in the path from switch to solenoid (like the neutral safety switch). But more common for the ignition switch to go out first. Either replace the switch or continue testing your start circuit. Post back with results or for further help. Good luck.

The ignition start circuit is the path from the ignition key in cranking mode to the solenoid on the starter. The path travels through a starter relay and a neutral safety switch before it reaches the starter.
This must be the circuit not working on your car.Make sure battery and starter connections are tight.Check for power at the starter solenoid terminal with a testlight when someone turns key to crank. If you have power there, they sold you a defective starter. If you have no power there then it could be the relay or the neutral safety switch.

Are you sure your battery is good and able to take and keep a full charge? The only thing in the start circuit that could cause a big drain on the battery is a shorted starter. But if you can send power and it cranks okay, I don't think you have a bad starter.

Is the ignition key on when you crank it and have no spark? Does your distributor rotor turn when the engine is cranking?

I would try a new solenoid. If it clicks it should send power on to the starter on the big cable. Make sure all battery and ground connections are clean and tight. If still a problem, buy a voltmeter and learn how to do voltage drop tests. This will help find bad connections.