my 78 280z recent started giving problems starting it up. i would have to turn the key about 5 or more times until it finally crankt. but only work for a while, now i have to started by bypassing the starter. i recently changed the starter so i dont believe it that. a friend told me that it could also be the neutral switch but at this point dont really know.

Could be the ignition switch, the ignition relay, or just bad connections at the starter.

when i turn the key it makes a clicking sound, but that it. does not crank

Could STILL be the Ignition Switch... poor contact = low current = clicking

Could also be a poor battery.

But I'm betting with Stephen... Ignition Switch. Check that first.

E

When we say 'ignition switch' we're referring to the plastic/metal piece that's screwed into the back of the ignition housing with the 5 pin plug plugged into it. (#1 in the picture) I'm only saying this to clarify because, based on your other posts, you may not know that it's set up that way. They do ocaisionally go bad and will cause the problem you're experiencing.

how can i check if they gone bad or not.

You can remove the switch and test is for continuity at the terminals as shown on the left side of the scan in post #5. What I usually do is reach behind the ignition pull the plug and plug it into a known working switch and turn it with a screwdriver. If everything works okay then the switch in the car is bad. Then I take it out and change it. I have several working switches. That same switch is in several Datsuns from the 70s and 80s and Subarus from the 80s so I've picked up a few of them over the years during trips to the junkyards. You can also buy them at Kragen for about 40 bucks or at Autozone for about 20 but they have to be ordered at Autozone. On the Z you'll have to remove at least the bottom half of the steering column cover to reach it.