Just bought my 280zx yesterday. All original 1982 non-turbo. Here's my issue - it will randomly not start, and when this happens, the battery will drain super fast while it's cranking. Sometimes it starts up with no problem. It started fine this morning, I took it to Autozone and they hooked up their battery checker and the guy said the battery looked totally fine. I turned it on and off at least 5 times in the parking lot. Then, when I went home and tried to start it again in the garage a few minutes later, it would just turn over slower and slower.

Side note- I just jump-started it with my truck and it started fine, but I noticed the voltage was hanging around 6 or so. So I gassed it a few times and it jumped up to 14. It stayed there for my trip around the block.

Could this still be a bad battery, bad alternator, or something else?

 

IMO it sounds like a bad connection/ground.

But i'm no mechanic.

 

mine did the same thing.. turned out the wires to the coil were loose and lose connection

 

Would just a bad coil cause this? I checked the primary winding last night and kept getting 1.4 on my multimeter. The Haynes manual says it should go no higher than 1.02. Does this mean there's too much resistance and not enough spark is getting to the ignition?

 

check your battery cables for corrosion. if you have those one size fit all clamp ons that people use cause too lazy to put new cables on probably the cause.