Zed Head

More from later.

Something different.

The display auction ends today, in about 2 hours, 40 minutes. One very early bid. Looks like some sort of odd attempt to generate interest in a bunch of scrap parts. E88 head on an F54 block. It doesn't even have value as a display engine. I bet that the bidder gets paid back by the seller and they both agree that it didn't work. Might also just be an advertisement for the shop. Using BaT for advertising. They got used, I think.

That is an odd first bid. Also odd that the seller is in the desert too. Hmmm.... Also also odd that the seller's chosen BaT name is harmonresto. Very similar to the old Harmony01 seller that puts stuff on eBay for inflated prices. All very strange! https://bringatrailer.com/member/deserthermit/ https://bringatrailer.com/member/harmonresto/

It was in a barn. There's potential. Looks like that back bumper was ripped off when they tried to pull it using a strap on the bumper. At this point, do no more damage while cleaning and inspecting seems in order.

Is this a real question or are you just showing the car? It's probably worth more as it sits than after parting it out. I don't know that I'd even try to start it. Post up more pictures after cleaning it up. Rust underneath is the big bad thing.

You could use a meter and see when it has power, if it does. Or if it's grounded or has resistance. I'd take a better picture from distance also. That's a great infocus closeup, but it's just a female bullet connection.

Just as vague in 1978. "engine accidentally stops while driving". ???

More -

Here's Nissan's view.

They could be counterfeits, who knows. Z Car Source is out of business now. Maybe that's part of the reason.

On a 76 one would be right around where the yellow is in this picture. An eyelet with a screw through it in to the manifold. The ground wire is in that harness. The alternator also has a dedicated ground wire which would provide grounding through the mounting points, assuming contact was good. Poking around with a meter is always fun. You could also use a headlight bulb to pull some amps through the various ground points. I like to measure things, but, adding a redundant ground wire won't hurt anything if you don't trust your measurements. https://bringatrailer.com/listing/1975-datsun-280z-45/

The premise of the added relay is that something along the circuit to the starter solenoid is drawing so much current that the solenoid can not actuate. The circuit has worked just fine for over 40 years I'd guess. Something is different now. The wire from R to the resistor bypass circuit is one of the few things that are different during Start. You have a "key at Start" voltage drop problem. Just offering troubleshooting paths to check. As far as the relays, there are several pictures on the forum of burnt/baked relay coils. They just get old and crusty with time. It's not just water that causes problems. How has it been starting with the new relay?

I missed the part above where you already installed the relay. Oh well. Don't overlook this part. Part of it is only in use at Start.

Nissan put the relays in an area that gets wet if the windshield leaks. If a crusty relay is causing excessive draw the extra bypass relay might just be delaying another problem. They're by the fusebox. I don't know if Nissan just changed names or did not use a standard ignition relay in 75. The 1976 BE chapter shows one but 75 only shows an "igntion interlock relay". They don't include the small diagrams either. 75 is one of the difficult years. This is the 75 drawing - Here's 1976, where that rusty picture above came from -

Interesting that the draw doesn't affect the other gauges, not even a needle quiver. But it does affect that horn noise. Not sure what that is, is it the seat belt warning buzzer? I have to say/ask - why are you avoiding the simple electrical diagnostic methods? It's a very straightforward circuit with a simple solenoid at the end. Low current, one device. I almost replaced my starter when the spade terminal lost contact but then I pulled back to the basics and figured out what was happening. Another time on a Ford Escort I was halfway down to the starter when my brain told me the symptoms didn't match what I was trying to fix. It was a loose battery terminal (not your case since the gauges don't move). Notice on the wiring diagram that there are other functions on that Starter wire from the ignition switch. You could check those to find the break.

Who is "they"? "Any or all of the above" doesn't mean anything. Z Car Source is out of business, AZC is more of a performance shop. Did you get them from eBay? Maybe you just bought from the wrong place.

The Tokicos are gas shocks also. There are some threads out there about how the gas shocks raise the car about 1/4 to 1/2". It's not much. You can push the shaft in easily by hand, it's probably only 20-30 lbs of lift. Who is Arizona Z Source? Did you mean Z Car Source? Or Arizona Z Car? http://www.zcarsource.com/ https://www.arizonazcar.com/

I downloaded the wiring diagram years ago from 240260280's AtlanticZ site years ago. It is excellent although it is black and white. http://www.atlanticz.ca/zclub/techtips/electrical.htm

1975 seems to have some odd features. The wiring diagram shows an "interlock relay". It exists for both Manual and Automatic. Could be involved. I don't know how it works. I think that the 74 260Z's have it also. @SteveJ knows about, I think. The diagram might be a holdover from the 260Z though. The 75 FSM does not describe it. Either way, your problem seems tailor-made for a test light with alligator clips. Set it up on the circuit you're testing, turn the key, see what the light does. If you get the click but the light stays on the problem is downstream. If the light goes off it's upstream.

I've seen that before too. Contact cleaner or Deoxit ia also a good idea. Deoxit is good everywhere actually. https://caig.com/deoxit-d-series/

If the aluminum stakes/posts/pins are still in the port I'd bet somebody might scavenge an old head for a liner and send it to you. Maybe. Post a picture of the linerless port anyway, if you can, just for viewing. Maybe it's fixable.

30 psi is about right if you have the vacuum reference hose connected to the FPR. The simple pump test is to remove the FPR vacuum hose, or disconnect the starter solenoid and turn the key to Start.

Two similar problems that I've had are a loose pin in the ignition switch, unlikely in your case, and a loose ignition wire connection at the starter solenoid. The last one seems possible. In my case the spade connection seemed to fit well but was not making good electrical contact. I crimped it tighter with a pair of pliers and it was fixed. You could rig up a wire under the hood to supply power directly to the starter solenoid terminal (or use a wrench or screwdriver to jump from the hot cable) and try it when the problem happens. Split the problem in to two parts at the solenoid terminal.

If you break it down to the basics, the whole point of the liners is to stay red hot and complete combustion of anything uncombusted. So, the action in the cylinder should not change. The 280Z exhaust manifolds are pretty primitive if you take a close look. The exhaust ports basically dump in to a large common chamber. I can't see a reason that the missing liner would do anything more than make one cylinder dirtier, emissions-wise, than the others. The EFI and emissions systems were advanced for the time, but pretty primitive today. This is just me, but I'd run it. Probably won't see a measurable difference. The converter will absorb one cylinder out of six's extra hydrocarbons. That's probably the only real effect. 75 and 76 didn't even have liners.