Strange starter circuit problem - help please

[Kerrigan]

The 1971 FairladyZ-L has had an intermittent problem with the starter circuit that just became non-operative.
It had occasionally giving out one "click" noise from under the dashboard somewhere, then the next time I turned the key to start the starter would work.
Yesterday all I get is the one "click" when I turn the key to start. Replaced the switch on the end of the ignition switch, replaced the starter, checked the battery.
When I use a jumper from the battery positive post to the b/y wire on the starter solenoid the car starts and runs with the ignition switch "on".
When I try the key to the start position, I get the click but no current in the b/y wire at the starter.
The wiring diagram shows an isolation switch for automatic transmission only; we have a manual five-speed. It's always started with the transmission in gear or natural, so probably no isolation switch for a manual trans?
No idea what is making the single "click" noise when I turn the key to start.
Is there a relay in the switch-to-starter that isn't shown in the wiring diagrams?
Any advice would be great!
Thank you.

 

[richiep]

I had exactly the same problem with my Z (a 71 Fairlady Z-L like yours) and it seems to be a relatively common issue in early S30s. The aging ignition circuit suffers from a drop in voltage across it so sometimes the starter solenoid doesn't get enough juice. The click is coming from the solenoid. There is a solution to this problem in the form of a relayed circuit that you can wire in that is triggered by the ignition and then provides a full 12V directly from the battery. You can buy a kit to solve this problem on eBay relatively cheaply; I just got the wiring diagram and instructions from the net somewhere (classiczcars.com or hybridz.org - I forget which) and bought the bits myself.

Here's a link:
DATSUN 240Z 280Z Starter Booster Relay Kit - 12volt | eBay

 

[Kerrigan]

In mine I'm not getting any voltage at all at the solenoid b/y wire. Not a single electron. The click is definitely coming from under the dash. We put a stethoscope on the starter relay and it was quiet when the click happens. Installed a new starter and same problem. The click sound is from under the dash. Is there a relay under there connected to the starter circuit between the ignition switch and the solenoid?
Thanks for the link; probably purchase it anyway. Replaced the switch on the end of the ignition switch too and it didn't make any difference.

I had exactly the same problem with my Z (a 71 Fairlady Z-L like yours) and it seems to be a relatively common issue in early S30s. The aging ignition circuit suffers from a drop in voltage across it so sometimes the starter solenoid doesn't get enough juice. The click is coming from the solenoid. There is a solution to this problem in the form of a relayed circuit that you can wire in that is triggered by the ignition and then provides a full 12V directly from the battery. You can buy a kit to solve this problem on eBay relatively cheaply; I just got the wiring diagram and instructions from the net somewhere (classiczcars.com or hybridz.org - I forget which) and bought the bits myself.

Here's a link:
DATSUN 240Z 280Z Starter Booster Relay Kit - 12volt | eBay

 

[andrew muir]

Hi
I get exactly the same issue now and again,
Did you find a solution.?
I usually give the solenoid a dunk and that seems to work. Only happens once in a blue moon abut seems to be gettinga bit worse of late.
Andrew Muir

 

[Throttleton]

I had the same problem on 3 of the 4 celicas I have had.
The first 2 I paid a fortune to have it fixed properly and on my current car I bypassed the ignition completely and put a starter button on the dash.
Having said that the electrics on a 240Z are simple.
richieps solution will work as that is basically what I did but on an old Datsun I would just try an find the fault, there isn't to much to confuse...

 

[Kerrigan]

It's not the solenoid; it's something in the wiring or the ignition switch which I'll be replacing tomorrow. No current at the starter end of the b/y wire.

Hi
I get exactly the same issue now and again,
Did you find a solution.?
I usually give the solenoid a dunk and that seems to work. Only happens once in a blue moon abut seems to be gettinga bit worse of late.
Andrew Muir

 

[Kerrigan]

Problem resolved! The ignition switch was only making contact to the starter solenoid circuit part of the time. The switch was bad. Replaced it and all is well! Also replaced the very old lug on the b/y wire at the solenoid. Replaced the starter as the other one was old and doggie, but it wasn't the problem. Spins like a top now! Thanks for all the advice and help.