SteveJ

The subharness for the fuel pump that Nissan designed for the 73 when trying to solve the issue of vapor lock consisted of two 4-pin relays. The power for the coil in relay 1 came from the neutral between the VR and alternator. It is a yellow wire. The power for the coil in relay 2 was the black/yellow wire from the starter solenoid. FP relay 2 was normally closed and cut power the fuel pump during starting. These two relays were mounted on the passenger kick panel with the wiper relay, horn relay, and AC (fan) relay. The device shown by the OP is mounted under the center console on the driver's side.

I'm thinking it might be the buzzer for the seat belts. My 73 has the same device.

Year?

I believe you'll find that the interior panels are going to be more like the 280Z (75-76) than the 240Z. If I can remember to take photos of my 260Z when I get home, I will post them. Then you can visually compare them to the 240Z trim panels.

I think I know someone in the local area who has knowledge of tracing electrical circuits.

We had a club drive to a BBQ place and later to a winery. The GZC refers to this as a wine & swine drive. Here are some photos from before the drive and at the BBQ place. With temps in the 90's, I opted to return home after lunch. I almost forgot to mention that @Tirnipgreen was able to join the festivities with us, though he skipped the initial drive.

How about a photo? Yes, it's from my 73, but I think the 70 would be similar. Yes, it branches off the main wiring harness.

That's the ground wire for the VR. It shouldn't be carrying a lot of current to begin with. I have a replacement in the box that I bought from BlackDragon (Victoria British) a long time ago. Let me see if I can find it. Meanwhile, I suggest you test resistance to ground on the engine side of the harness where that wire connected to. Frankly what catches my eye is that loose green wire.

The wiring work is getting inspected, and I've barely even started.

On the other hand, I did use some of the parts in the hardware kit. I can't remember which parts because it was many years ago.

Yep, it's the ECU. When you have to resort to percussive maintenance, it's pretty much ready for a restoration.

Jump 1 to 5 & 2 to 3. I even found a source for the 6 terminal connectors to make a nice looking plug for the VR connector.

Solenoid was the wrong term. I apologize. That's what I get from going by memory. Look in the EC section of the FSM. On the bottom right of EC-10, you get a very vague description of the throttle opener. That is what prevents the throttle from slamming shut when you are off the gas quickly. Basically, it uses the engine vacuum to keep the butterflies open some to prevent an overly rich condition. When the 280Z came out, the system that car used is known as the BCDD or boost controlled deceleration device.

But is the solenoid working?

Does your car still have the solenoid to keep the throttle from slamming shut when you get off the gas? If it doesn't, then you have a sudden rich condition when you lift off the gas.

There are easier ways to find that 10mm socket you dropped.

Vredestein: https://www.vredestein.com/classic-tires/products/990-SPRINT-CLASSIC/

They were on both sides. You can see the other side here: https://www.brelegacy.com/mm5/merchant.mvc?Screen=PROD&Store_Code=B&Product_Code=photo240z_image008&Category_Code=brearchivephotos240zs And here is the passenger side of the 3 car: https://www.brelegacy.com/mm5/merchant.mvc?Screen=PROD&Store_Code=B&Product_Code=bre2_240_3_ocraceway_002&Category_Code=brearchivephotos240zs

Search for LED list. The updates from October of last year are the latest. Vendors on Amazon change their product lines, so some searching may be required. Auxito for the bulbs Koito via Toyota for the H4 housings or Hella.

And THAT is a good reason to consider their product.

By the way, if you go with the brand bulbs I recommend, they are polarity independent so you don't have to incorporate relays into the headlight circuit.

No. I have done the H4 with LED bulbs MANY times without issue. @HusseinHolland did the same thing with the parts I recommended. No problems.

Why? H4 housings with H4 LED bulbs work fine in stock buckets.

The hole on the thermostat is threaded as BSPP. I don't think ACE will have that.