Help. Ignition switch or something else?

[iufan993]

First time problem. When key goes to accessory position, everything seems to work: radio, interior lights, Interior fan.  When I switch to “on” position, all interior lights dim. When I turn the key to the right, The starter never attempts to turn over and all electrical except for the clock shuts off immediately.  If I remove the key for about a minute, I can put the key back in and have the same accessory position items powered up. Of note, even in the accessory position, if I draw an amp load (for example the power antenna or turning the fan up) everything will shut down again for a couple of minutes. It’s like anytime I apply an electrical load a breaker is breaking and then resetting. 
 

In my experience, this would always seem like a ground issue. The battery is new and all wires tight.  I have 15.9 amps at the starter solenoid.  
 

Is this just a typical issue for the ignition switch, or is this more likely to be in the fuse relays?

I assume the “on” position powers the ECU and the fuel pump, but I feel like any load in the system, no matter what position the key is in, will shut everything down.
 

 

[SteveJ]

What year?

[Captain Obvious]

First thing to try... Clean your battery terminals.

[iufan993]

1975. Battery terminals spotless

[Zed Head]

Are the battery terminal clamps tight?  Sure sounds like a connection opening up due to heat from high current across a loose and or dirty connection.

The ignition relays on the 280Z's were put in a spot that gets wet if there's a leak.  Same reason, different location.  Current heat.

[dutchzcarguy]

8 hours ago, Captain Obvious said:

First thing to try... Clean your battery terminals.

Clean the terminals inside also.. i had this ones, voltage on the pole 12,2V, on the terminals 0Volt!  They looked very clean but there was a isolating layer of oxide between the poles and connectors!  If i had'nt measured it with my meter i wound'nt have found it so fast! clean them (brush) and use some petroleum jelly (we (Dutchies) call it vaseline).

[dutchzcarguy]

8 hours ago, iufan993 said:

 I have 15.9 amps at the starter solenoid.

You mean 15,9 Volts ??   a bit much?  is that from a good meter instrument or a 5 bucks toy?  ?  What you could do is put the voltmeter on the starter and let someone start the car, what does the meter say?  my guess is 1,2 Volts... when starting (trying to) ..

clean also all grounding leads.

Edited August 30, 2020 by dutchzcarguy

[iufan993]

 The battery terminals were fine, but this spade connector on the positive side near the firewall was corroded. Problem solved.  

[SteveJ]

Green wire? That may be the EFI fusible link.

[iufan993]

Red wire with black sheath

[SteveJ]

33 minutes ago, iufan993 said:

 The battery terminals were fine, but this spade connector on the positive side near the firewall was corroded. Problem solved.  

That's a red wire?

[Captain Obvious]

Glad you're out of the woods for now but I'm not sure that was really the root cause.

I think the corroded connector you found is the fusible link for the EFI system (and only the EFI system). If that's the case, it could account for the car cranking fine but not starting. Corrosion there wouldn't account for the rest of the symptoms you had.

I'm thinking that while messing around up by the battery and cleaning that connector, you bumped whatever really WAS causing the issue. Hope not, but it might come back.