1975 280z 2+2 will not start

[zclocks]

I was reading your post from the beginning and have a question. When you said the car wouldn't start did you mean the engine wouldn't turn over or it turns over, but will not run?

Also the relay you showed is a Bosch std 30 amp relay that is used for everything and mostly in alarm systems. If this is hooked to your start switch the PO might have tried to by pass the wiring to the  starter because the car wouldn't start. I had this problem with my 75 and have seen it on more than 5 cars over the years. look at the crude diagram I have drawn.

I currently employ this relay because it eliminates running a high current through the ignition switch that if shorts in the steering column causes all sorts of problems.

Edited September 29, 2020 by zclocks

[iscnetwork]

Car turns over just fine with a screw driver from battery to solenoid.  I haven't had the chance to look at the relay discussed above yet and may not get one today either.

My yellow wire that goes to that relay or the solenoid is dead.  I probably will re-enable the 'non-factory' relay.  I do not like high amps in the ignition switch either.  Thanks very much for the 'wiring' pic & diagram.  I am trying to be real cautious so I don't fix one thing and then fry something else.

Edited September 29, 2020 by iscnetwork

[Zed Head]

9 hours ago, iscnetwork said:

My yellow wire that goes to that relay or the solenoid is dead.  I probably will re-enable the 'non-factory' relay. 

The yellow wire would have been the wire that actuated the relay.  Not really clear how your setup ever worked, if the yellow wire does not get voltage when the key is at Start.  And the coil, or the wire to the resistor, should have voltage when the key is On.  

Find your ignition relay, by the fuse box, and see if it's been getting wet or if it's rusted/corroded..  Seems like you have a circuit broken between the ignition switch and those parts.

[iscnetwork]

I am working backward from the yellow wire that originally activated the aftermarket relay to fire the solenoid.  The interlock-relay coil shows 40 ohms, contacts are not fried. Wiring plug to it is fine. So now according to the wiring diagram the blue & blk/red wire from the ignition-interlock-unit power the coil to activate this interlock-relay.

The needle in the haystack is starting to look easy to find.

Going to pick up ignition switch so I can remove the MSD.

I am hoping the ignition-interlock-unit is actually a relay so I can test it too.

 

[Zed Head]

I just learned something.  I did not know that 75 still had the interlock relay, I thought it was just 74.

Here's the page from the 75 manual.  I'd check those seat switches.  It reads like you have to have your seatbelt fastened also, IF you're sitting in the seat.  Or, just reach in the window with no one in the car and start it.  Very safe, start the car in gear with no one inside.  And, there's a button you can push in an emergency.

I would just bypass that relay entirely.  What a kludge-up.  Good luck.

[Zed Head]

There are two diagrams, both show a neutral device, either a relay or a switch.  They didn't label the diagrams though so it's not clear which is for what.  One shows an inhibitor "SWICHT" so maybe it's for the automatic.  So glad I got a 76 instead of a 75.

Edited September 29, 2020 by Zed Head

[Zed Head]

This is probably for the manual.  "Emergency sw" is probably the button.  That might be a good area to bypass the interlock. Just jump the button circuit.

Edited September 29, 2020 by Zed Head

[SteveJ]

36 minutes ago, Zed Head said:

I just learned something.  I did not know that 75 still had the interlock relay, I thought it was just 74.

Here's the page from the 75 manual.  I'd check those seat switches.  It reads like you have to have your seatbelt fastened also, IF you're sitting in the seat.  Or, just reach in the window with no one in the car and start it.  Very safe, start the car in gear with no one inside.  And, there's a button you can push in an emergency.

I would just bypass that relay entirely.  What a kludge-up.  Good luck.

 

While the seatbelt interlock was removed from the regulations, it was too late to remove it from production vehicles.

[SteveJ]

23 minutes ago, Zed Head said:

This is probably for the manual.  "Emergency sw" is probably the button.  That might be a good area to bypass the interlock. Just jump the button circuit.

This is what I posted in the past on the seatbelt interlock relay: 

 

 

[iscnetwork]

yuk.  Now if I can find the emergency button.

If I get any time tonight I am going to remove the MSD, a screw driver should then at least start the car with ignition turned on, regardless of all of this goo.

 

 

[iscnetwork]

Thanks for the tread & pictures everyone.

 

[Dave WM]

My 75 does not have any of that stuff as far as seat belt interlocks or emerg switch buttons. Maybe was removed at some point in its life.  Just reach in and start it. in gear out of gear, etc...

Darwin was consulted as to how to prevent problems.