yeah just sounds like dirt, rust, and old... take a wire brush and go to town

By the way, it usually happends when i turn the key slowly, step by step BUT if i just quickly turn it from off to start it starts right up. Weird. Got to look this today.

Seems like the switch contacts behind the key.

Now this problem has a new turn: Z turns off when driving.. I was driving almost fully heated engine and then just like lightning from the clear sky, it turns off. I tried to start it but it didnt, well it did start but died instantly. I removed the ground cables and put them back. After that it runs great.

Pleez help.

Does tach stop instantly when engine dies or does it mach engine speed and chug to a stop slowly?

Tach stops instantly..

That indicates the problem is with your ignition system. I am not sure what is on your Z. Do you have an electronic ignition system or an old points system?

The problem could also be a relay in your ignition system but that seems less likely.

Old points system, this symptom seems to get worse by day. I can hardly start the car. I have brand new starter but could it be it?

If the car cranks then the starter is fine.

If the car dies when driving and the tach immediately goes to Zero then it is ignition problem.

The 4 areas to check are:

1) The condenser (capacitor) (In '72 FSM it is item 10 in drawing EE62)

2) The coil

3) wires in the ignition system

4) distributor mechanical parts (points)

refer to the FSM.

My old Toyota Tercel had a failing condenser in the distributor that would kill the spark randomly but it got worse and was temperature dependent. It was a $1 part.

The coils is a $20-$60 part to replace.

Adjusting points is free.

Checking for loose wires is free.

Reason for the starting failures was 1 year old (!!) Chinese ignition switch base. I switched 40yr old base back and it started to work. Hot damn these Japanese dudes can make everlasting electronic.