The headlights and all the accesories are in working order, but the car won't crank. Acting like it has a dead battery or something but it doesn't. The battery has quite a bit of power in it (tested it). You can hear the relay but it's not cranking. What could this be? Did my alternator go out? Any help ASAP would be helpful..rizz?

 

There are a couple of things. You said you hear the relay? Do you mean you hear the started solenoid? If you hear a clicking when you turn the key, then that's the solenoid. If that's the case, then it's probably a bum starter solenoid, or the starter itself. Sometimes the solenoids are external, but I think the Z has the solenoid internal; which means you need to replace the starter.

If you have an alarm that has a starter disable feature, check the ground wire for the alarm. The alarm will not allow the car to start if the alarm is not connected. make sure the alarm ground wire is nice and tight. I had that happen on my car.

Another possibility is corroded battery terminals. Try cleaning off your battery terminals and give it a shot.

If you have power to the accessories, then your alternator and battery are most likely fine.

good luck.

 

Yeah that sounds about right.
What year is your car? I'm wondering (if it's old enough) if it might be the ptu....hmmm.
If you have an alarm, like aforementioned, try temporarily disconnecting it.
I don't think he has a problem with the starter relay/solenoid if he can hear it clicking. It clicking means that it's doing its job.
I'd just recheck all fuses and fusible links inside and outside in the engine compartment. If it isn't any of those, then I'd start looking toward the starter.

http://www.300zx.co.uk/cgi-bin/manua...ault&total=133

step by step diagnosis of the starting system. enjoy