Everything works electric wise, so not battery. Turn key in ignition and it does nothing. Like it's immobilized. Thinking starter motor or wiring thing. Has happened before then after a few hours it started no worries. I have an AU2 Futura Classic 2001 model.

If the starter is good and the relay is good, but the ignition wire on the starter is not getting power, it is possible that there is an issue with the ignition switch or the wiring leading to it. Here are some steps you can take to troubleshoot the issue:

1. Check the battery: Make sure the battery is fully charged and in good condition. A weak or dead battery can cause the starter to fail to receive enough power to turn the engine over.
2. Check the ignition switch: Use a voltmeter to check for voltage at the ignition switch. If there is no voltage, the switch may be faulty and need to be replaced.
3. Check the starter relay: Use a voltmeter to check for voltage at the starter relay. If there is no voltage, there may be an issue with the wiring or a faulty relay.
4. Check the wiring: Check the wiring leading to the ignition switch and the starter to make sure it is not damaged or disconnected. A damaged or disconnected wire can cause the starter to fail to receive power.
5. Check the immobilizer: Some vehicles have an immobilizer that can prevent the engine from starting if the key is not recognized. Make sure the key is properly programmed and try a spare key if available.

If none of these steps resolve the issue, it may be best to have a professional mechanic diagnose and repair the issue.

To check the starter: key off, transmission in park or neutral, brake set. Pull off the small wire to starter solenoid. Then use a small jumper wire from battery cable post on the starter to the solenoid terminal (can also use a small screwdriver to bridge those terminals). Starter motor should engage the flywheel and spin the engine. If nothing, starter motor or solenoid is bad. If starter works, check for power on the small solenoid wire, with key held in crank. Wire should have power, if not, check start circuit from ignition switch to solenoid-the neutral safety switch is in that circuit.

Is it getting fuel? Check the pressure regulator or the fuel pump. Even if you have the plug wires on wrong it should do something.

See, the starter gets power from the battery it also gets power from the ignition switch. When you turn the key the solenoid closes and supplies power to the starter motor. So if you are hearing a click the solenoid is getting getting a signal from the ignition switch. Check for power from the solenoid to the starter motor. If it lights up that means power is being transferred to the motor and the motor is either bad if it doesn't turn the engine or the engine is locked up.

check that you have the starter wire on the solenoid correctly
whne you say power to the starter --is that from the battery lead or the small control wires from the ignition switch

If the battery is fine, why jump it? Faulty thinking to state or think: all electrical in the car work fine. If it did the starter motor would be turning the engine over. The starter motor work on electrical...not all is fine.

check: 1) 60a starter fuse/relay. 2) voltage to starter when turning key to activate starter motor, this will rule out ignition switch or relay. 3) apply direct voltage to starter motor to detect bad starter motor.

bench test starter motor

Thai is either ignition cylinder or starter coil, or a problem with starter motor/wirings to starter motor.

The starter motor must be energized directly (in neutral, and possibly using a remote switch) to check that is working.

If the starter motor is fine, check that there is power coming to starter motor when you ignite.
If there is no power, test power at ignition and eventually replace ignition.

If you leave your ignition key in the normal running position and then slip underneath your car from the rear of the passenger's side front tire, you can slide forward to see the starter and it's solenoid on it's backside. If you take a screwdriver and short between the smaller, center screw on the solenoid and the upper, larger screw (or bolt) you should get a spark and the sound of the starter motor cranking over the engine. Explanation: The solenoid tends to get sticky after a while and becomes reluctant to go back to it's "at rest" position. After driving the car awhile it normally falls back into place.

My Nissan Primera EGT (1993 Reg'd) has an immobiliser, which was causing a similar problem. Turned on ignition and nothing. The immobilizer was faulty to the starter motor, so we disconnected it from the starter and left the immobilizer on the fuel line. Starts now, no problem and the immobilizer would still stop the potential thieves as they'd have no idea without the immobilizer key why the engine will no more than start then stutter to a big full stop!!.
The 240SX is probably a more modern Nissan but I bet there's an immobilizer built into it somewhere. You may need to take it to a Nissan expert or Dealer to check out. It's almost definitely something weird like an immobilizer or maybe the starter motor's blown it, but then you'd have heard the graunching noises that starter motors make when they're about to clap out, they don't usually just go. There may also be some disconnection of wires to the alternator, which amplifies the spark to the engine, but the starter motor would still turn, your engine just wouldn't fire up with the too weak spark. So if nothing moves, it's most likely an immobilizer or possibly (but unlikely) a sudden death starter motor.