SteveJ

Since carb cleaner or starting fluid is flammable, your engine treats it as fuel. If you have a vacuum leak along say a gasket at the insulator blocks, that leans out the engine. When the carb cleaner gets pulled in through that leak, your mixture isn't as lean. Another method I've used in the past was an unlit propane torch. You barely crack it open, and when you get near the source of the leak, you'll hear the engine speed increase.

Make sure the gauge body is in firm contact with the chassis. If you were testing the gauge without having securely mounted it in place, it would not have the ground for the lights. If you did have it attached with screws, examine the gauge and dash mounting points for rust or other debris that would insulate the gauge body from the dash.

Welcome. Do yourself a favor and download a copy of the factory service manual to start off. It has a lot of the information you will need to maintain your car. You can find a link in my signature, though I'm not sure the signatures show up on mobile devices.

Incorrect. The 280Z does NOT have relays in the headlight circuit. All of the current for the headlights go through the contacts in the headlight switch. This means the contacts can foul, just like they do in the 240Z switches. Therefore, the 280Z would benefit from a conversion to relays. The catch is that the connectors changed between the 240Z and the 260Z. While Dave Irwin @Zs-ondabrain was able to source the 240Z connectors, he could not find a vendor that had the 260Z/280Z connectors. That is why there is not a plug and play solution for the 260Z/280Z. Dave has made custom relay harnesses for owners of those cars who have supplied their own connectors. Keep in mind that a voltage drop will severely curtail light output of the headlights. (https://www.danielsternlighting.com/tech/relays/relays.html) About 16 years ago I did a relay conversion to my 240Z. The voltage at the headlights (with the car off) went from 9 to 12 volts. That means the headlights were about twice as bright as before.

10 AWG solid wire: https://www.amazon.com/Ground-Wire-Copper-Listed-SATELLITE/dp/B00JJTPWII You can also get 8 AWG bare solid wire from Home Depot or Lowes for 59 cents/foot. That's a little over 1/8 inch in diameter. It should fit inside the return line easily.

Glad you found it.

You're not going to make this easy. Okay, this will take some thinking. You weren't supposed to the proper results on EVERY test.

Or I have a 73. The 73 was the first with intermittent wipers, so the combo switch has a 9 pin connector on the headlight switch side.

No problem. Now I can make sure I'm looking at the right wiring diagram. What I'm afraid of is that someone put in more than just the one wiring hack we see in your photos. We already know of one cross-linked circuit. There may be others. It will require a visual inspection on your part to identify where they are and what color wires are involved. The butt splices may help us in locating them. When you took out the dash, were there any connectors already apart? If there were and you remember where, that may help us further.

Well, your first problem is that when a circuit failed, someone decided to jury-rig a fix by tapping off of the white/red wire instead of figuring out what is wrong and fixing it properly. Is your car a North American spec car? What year? The wiring looks like a 73. Please let me know so I might be able to give better suggestions. Do you know how to use a volt/ohm meter? It will take some time, but we can figure this out.

If you are getting random results that you can't figure out, the best thing is to stop and be methodical. Refer to the PDF file in that link for references. Measure voltage to GROUND at the white/red wire at the dash to steering column connection with the brake pedal applied. You should be able to get the positive probe of the meter inside the connector enough to get voltage. You should get battery voltage there. If not, do the same test at the same connection on the green/yellow wire. If that test fails, repeat the same test, measuring the green/yellow wire on the 6 wire connector at the dash to hazard switch connection. Report your results. If the first test passes, go to the dash to body harness connection. IIRC, that should be on the passenger side footwell. You can confirm this in the BE section of the factory service manual. Use something to weigh down the brake pedal, and repeat the same test on the green/red wire. If that test passes, move to the rear panel connection on the left side, and repeat the test on the green/red wire. Report your results. Finally, make sure the brake pedal is not depressed. Check the resistance to ground from the black wire on the rear panel connection. Report your results. Unless someone has hacked into the wiring harness, those tests should indicate where the problem lies. Also, you did not say. Does the front left light work for the turn signals and emergency flasher?

So, from what I have read online for the past 20 years or so and from personal experience, here's a list of things I have seen that can cause the fuel starvation problems similar to what you are experiencing. Rust/debris in the fuel tank. Cracked hard/soft fuel lines that allow air to be pulled into the fuel lines. (I suppose loose connections could fall into this category.) Kinked fuel lines or some other blockage. (Personal experience there from when I replaced old, rotten stock rubber hose with standard fuel hose and didn't watch the bend radii.) Clogged fuel filter. Bad fuel pump aka leaking diaphragm. (Make sure your oil isn't smelling like gas.) Bad floats. Improperly set floats. Blockage at the SU filters. Being an electrical engineer, I look to divide the circuit (system) to assist in diagnostics. Check the fuel pressure downstream of the mechanical pump, aka between the pump and the carburetors. If it is good, you can focus on 6-8. If it is low, focus on 1-5.

Holy crap! Why didn't I think about this? I could put the food next to the valve cover between cylinders 3 & 4. That would have blocked the heat coming up to the fuel rail. Not only would I have solved the heat soak problem I was having, I would have had a hot lunch, too!

This may help you with the circuit. It describes how the circuit works so you can track things down with a voltmeter. Look it over and ask questions if you still have trouble with diagnostics. https://fiddlingwithzcars.wordpress.com/2013/01/20/hazard-switch-brake-light-turn-signal-circuit-analysis/

I would suggest searching at http://www.hybridz.org. Search thoroughly before asking. I wouldn't be surprised if you have to mock up things yourself to find out.

I'm hoping it looks a lot better after I receive and install the Aeroquip support clamps to hold the hose in place. A friend on Facebook did something similar with banjo fittings to the SUs. I asked him for more information on that.

In God's country up in NE Forsyth county.

Ugh. Still ITP.

Where are you moving to and when? I might be able to pay you a visit soon if needed.

I replaced the fuel rail with braided lines, placing them closer to the carburetors and away from all of the heat of the engine. So far, I have not been able to replicate the heat soak problem I was having before. Maybe I finally slayed the dragon.

There isn't a driver side strap on my 73 either.

You don't have to bring your Z to the meetings. I brought my daily driver to the last one since SWMBO accompanied me and wanted the luxury of AC. Send me a PM with your contact info, and I can get you hooked up with my people. I'm going over to Lawrenceville at noon today to get help from a friend to install braided fuel lines in my car.

Something is definitely not right with the length of that brake hose. I've never had one kinked like that.

Thanks for tagging me, @Zed Head. @eloZada, there are a lot of great S30 guys in the ATL. Many of us work on our cars at home, and some guys even have their own shops. A lot of them are members of the Georgia Z Club, too. You can track me down through the GZC facebook page. If you don't happen to be on facebook, you can keep up with the GZC at http://georgiazclub.wordpress.com This is a great time to be a Z owner in Atlanta. We are in the planning stages for the 2018 ZCON here. Get involved. Meet the guys. Have fun with your Z.

Carl, MikeB linked the commercial I was referring to. Randy is going to talk to Mark Lambert about bringing Mark's 240Z for the beauty shot at the end of the commercial. Edit: Thinking about it, it might be nice to have a flood of BRE tributes, too.