With a screw driver the engine turns over just fine.

Where are you putting the screwdriver?


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+ Battery terminal on starter to solenoid connection.  (bypassing the relay).

you are going to want to get a factory service manual pronto. will help a lot with diagnosing issues. As mentioned do your lights work (regards of ign switch they should work if the batter is hooked up), same with the horn. do you hear a relay click under the steering wheel when you turn the key to "on" Have you checked the fuse links in the battery cable? A test light is your friend when chasing electrical issues like no start.

2 hours ago, iscnetwork said:

Fuseable links not that dirty, cleaned anyway they have continuity.  Still no good. 
Solenoid to relay wire was not that dirty, cleaned anyway.  I will attempt to pull that relay out tomorrow and make sure of its connections.

The point about the links was not continuity through the links, but connection with the terminals.  Continuity through the wires that are connected to the links.  You check that by measuring voltage, not continuity.

A 1975 280Z should not have a relay between the solenoid and the wire from the ignition switch.  Unless the car started as an automatic.  But, even if it does, the test would be to measure voltage at the relay activation wire when you turn the key to Start.

No offense, but when you have a meter you don't need to do a bunch of cleaning.  You just use the meter to tell you if the connections are good.  Cleaning without using the meter doesn't tell you anything.  You didn't use the words meter or measure once in your post.  Not good.  EFI is all about the meter.

2 hours ago, iscnetwork said:

+ Battery terminal on starter to solenoid connection.  (bypassing the relay).

Actually that bypasses ALL of the car's wiring.  All you need for that are the battery cables.

8 hours ago, Zed Head said:

Actually that bypasses ALL of the car's wiring.  All you need for that are the battery cables.

I was hoping with key on, it would start.  My 240z would.  I was trying to do anything to get the car out of the cramped garage so I could actually work on it.   It needed the brakes adjusted and a leaking fuel pump replaced with I parked it.

Edited September 24, 20204 yr by iscnetwork

Good, I can remove the relay then.  I was planning to dig it out and see if anything else but the solenoid was going thru it to "wherever".  I have used a VOM as I go.  I test the links just to make sure they were not fried.  I had an American one once look good, dead as a door nail.

10 hours ago, Dave WM said:

factory service manual

Best place to find?  Looking at ebay, I have a clue which one. 

Has anyone scanned one here?
 

Lights work. Horn is disconnected (previous owner put on a racing steeling wheel).

Edited September 24, 20204 yr by iscnetwork

19 minutes ago, iscnetwork said:

Best place to find?  Looking at ebay, I have a clue which one. 

Has anyone scanned one here?
 

Lights work. Horn is disconnected (previous owner put on a racing steeling wheel).

The scan for the 75 is missing sections. Download the 76 as well.

Edited September 24, 20204 yr by SteveJ

2 hours ago, iscnetwork said:

Good, I can remove the relay then.  I was planning to dig it out and see if anything else but the solenoid was going thru it to "wherever".  I have used a VOM as I go.  I test the links just to make sure they were not fried.  I had an American one once look good, dead as a door nail.

Could you post a picture of that relay?  A PO must have installed it for a reason.  Might be that they were trying to fix the problem you're having now.

Are you sure the car did not start life as an automatic?

I made sure the lights, turn signal, etc. work with key on/off as these all should.

For sure the relay is aftermarket "Made in China". 

It had 4 wires, 1 yellow 18 gauge, 2 red 10/12 gauge one to battery connection on starter and one to the solenoid, 1 ground.  1 Empty pin. 1 Ground.

Wiring harness that runs along the side of the engine goes to a plug (pic #1) then close to the plug the oil sensor wire comes out of the wrap, up about 6" the yellow 18 gauge wire comes out.
To save a bunch of writing is the Yellow wire that the end fell off the original solenoid wire (#2)?   It is about 18 gauge yellow colored.  IF so I can fix this part of the mess.

That ball of tape in #3 I think was a plug that was cut off for the MSD ignition.

So why I have no voltage at the coil is still a mystery.  I haven't had the time to go thru the manuals given to me above. 

 

28 minutes ago, iscnetwork said:

To save a bunch of writing is the Yellow wire that the end fell off the original solenoid wire (#2)?   It is about 18 gauge yellow colored.  IF so I can fix this part of the mess.

See if it gets 12 volts when you turn the key to Start.  

The early 280Z's have yellow wires that go to the brake check warning lamp and other places.  Do you see a voltage regulator?  Might be that somebody wired in an internally regulated alternator.

Looks like you're at the start of finally learning what a PO did to your wiring.  Condolences for the pain that's in front of you now.  If you have an MSD ignition it might be that your original electronic ignition module has been bypassed.  And, maybe, the PO decided to wire in a relay for the coil also.  It's looking like somebody just hacked in the wires needed to make it run.