82 280zx Starting issue: New (and charged) battery and good starter.

[whitezeppelin91]

I've been trying to diagnose this problem for a while now and I'm stuck now, so I decided to post on here.

vehicle: 1982 280zx non-turbo, automatic tranny

here is the problem:

My car will turn on (initially). I mean all the way to the on position and the dash will light up. I can hear the fuel pump, etc.

Once I turn the key to the start position I hear one click and the the dash turns off and the volt meter on my dash goes all the way down.

When I put the car into the on position (after attempting to start it the first time) the dash doesn't turn on and the voltmeter (on the dash) goes all the way down again.

I tested the battery 12.6V

when I checked the volt drop between the pos post on the battery and the battery cable it dropped almost 12 V.

The only way that I have been getting it to start is taking off the neg battery cable for a while (I think to reset the ECU). after I wait like 10 seconds, I can put my car into the on position and the dash will light up again. When I try to start it, it sometimes kicks over and the engine will turn and idle at about 800-900rpm(nothing to do with temperature I dont think). But as of now, this trick does not work.

what I know:

new battery

new starter

alternator seems to be weak (haven't tested it because I can't start the car.)

any help or guidance from a seasoned z car owner would be much appreciated.

Thanks!

[Wade Nelson]

Let's clarify. Is this a NO CRANK or a NO START problem.

If it's a "NO CRANK" problem.

pull the small wire off the starter solenoid. Run a jumper wire from B+ (battery positive terminal) to that lead. If the starter cranks, the problem is somewhere between that wire and the battery, through the ignition switch, etc.

[whitezeppelin91]

No crank problem.

I had trouble with it today.

I think it has to do with the triggering system on the starter or maybe just the trigger wire.

I'm going to test the trigger wire today.

Does that sound like it could be the cause or am I thinking incorrectly?

[Zed Head]

The only way that I have been getting it to start is taking off the neg battery cable for a while (I think to reset the ECU).

Sounds a lot like a bad battery terminal connection. They get dirty and/or corroded and will pass just enough current to run everything but the starter. When you take the negative terminal off do you clean it and put it back on tightly, or do you leave it loose so that you can get it off easily the next time the problem happens? They need to be clean and tight.

The ECUs on these cars don't reset at all. The only thing on the car that changes when the battery is disconnected is the clock.