SteveJ

There is an issue with the VR in the alternator.

No charge indicator light. What is the voltage at the battery when the car is running? I'm wondering if there might be an issue with the internal voltage regulator. Remember that new does not always mean good.

Two wires were tapped: the neutral (yellow) wire between the VR & alternator for the fuel pump relay with the normally open contacts and the black/yellow wire for the starter solenoid was for the fuel pump relay with the normally closed contacts. The tap for the neutral was actually small harness Nissan designed to go between the VR and engine harness. I pulled it out of my 73 a long time ago.

Unfortunately, the 73 wiring diagram won't show it, either. It was added on later. Download this file and look at the mounting points for the relays: https://www.classiczcars.com/files/file/60-fuel-system-modification-plus-73-74/ Also, is the hazard switch a pull switch or a toggle switch. 73 was the only year for the pull switch.

Actually if you suspect an air leak, replacing the rubber lines would be a good start and could alleviate the need for a check valve in the engine bay. If the rubber lines are allowing air in, they can allow fuel out in the future.

I learned from @Captain Obvious that one of the things to consider on a check valve is cracking pressure. Most likely the fuel pump will overcome the cracking pressure on the check valve, but I couldn't find the cracking pressure listed on the Amazon page. For instance, these Evil Energy check valves have the specs listed on the page: https://www.amazon.com/dp/B0FQHSSLN5

That build date would typically indicate a 73, though some states may have titled an 8/72 as a 72 back then. https://jdm-car-parts.com/blogs/news/vin-verification-of-us-datsun-240z-260z-280z-280zx?srsltid=AU7gw4VZKuT31B6faCZYskqAm_f9DiAZx3ONK3Xsnn_scBm8EpKTCGA-

What is the build date of the car? Can you have someone else unplug and plug in the T connector on the alternator while you listen for a relay clicking in the passenger footwell?

I have a habit of researching parts when I hear of people having problems in case I have that problem later or to come up with improvised fixes should original style parts not be available. Recently I was researching vacuum solenoids in case someone with factory AC in a 260Z or 280Z needs replacements. I saw some Infiniti vacuum solenoids that may be adaptable for that.

If you decide you want a new radiator, this one is closer to stock than an aluminum radiator. https://www.rockauto.com/en/moreinfo.php?pk=8609984&cc=1209170&pt=2172&jsn=575

Can you not locate the fill plug? It's a little above the drain plug at the red arrow. You should be able to get an open end wrench on it. I'm not sure if it's 17mm or 19mm. There is the chance someone installed the later fill plug. Those might take a 1/2 square drive. The problem there is the cross member could be in the way of accessing it. You should be able to fit a short extension from a ratcheting wrench into the square plug to remove it.

Does your air cleaner look like this: Or this: The air filters for the top one are pretty hard to track down anymore.

I remember you mentioning that, and while I suggested it to my friend, he wanted the pad instead. 😆

A friend called me saying his brake lights would not turn off. Long-time members of this board are probably thinking that it's the the brake light pad at the pedal. That's what I guessed, too. And all of you would be right. Since he's an older gentleman, he asked if I could fix it for him, but he couldn't bring me his car for a couple of days. With that delay, I decided I could do an experiment. I bought a Dorman 74025, brake pedal stop pad kit from Amazon because it's designed for Nissans. I wasn't too worried about Amazon saying it wouldn't fit. My friend drove up to see me this morning, and I had the clear pad in my hand. As soon as he got out of the car, I leaned under the steering wheel to press the brake pedal and pushed the clear pad into the hole. I picked up the remnants of the old pad off the floor mat and handed it to him to show him that it basically rotted and fell apart. The nice thing about the Dorman 74025 is that I verified that it's frequently in stock at O'Reilly's, Auto Zone, and Advance Auto Parts. Napa has the part number 74025, but I don't know if they use the Dorman packaging. If you have Amazon Prime, you can probably get it overnight or the day after if you can't make it out to the parts store.

Thank you for caring enough to try to get it right.

@LeonV I agree with you about crush washers being better than teflon tape, but there is teflon tape designed for use with gasoline and oil, such as Gasoila YT70.

You are correct.

Several members of the Georgia Z Club went to a charity car show. It turns out we were a significant percentage of the cars that showed up. Unfortunately, no one brought a Z31 or Z34, but we had good representation otherwise.

No, we secretly decided you're the guinea pig.

Yes. These circuits are powered off the ignition relay.

Did you install new calipers? If so, make sure the bleed screws are at the top of the caliper. It wouldn't be the first time someone swapped left and right calipers.

The purpose of this post is to help give people an idea of how I approach diagnostics to assist with their own troubleshooting. Scenario: 78 280Z with no low beams Background: My friend was working on another person's 280Z and found that the headlights were not working. He checked the high/low beam switch and found it need of repair. However, after repairing the switch, he could only get the high beams to work. He asked if I could assist with the diagnosis and repair. Diagnostic process: First I verified the problem description. The high beams would work, but the low beams would not. I backprobed the connector (inserted the meter probe on the back of the connector) at the steering column with the other probe connected to the negative post on the battery. I checked for resistance to ground and found both the high and low beam positions showed acceptably low resistance on both sides of the connector. Note: Since the resistance to ground readings were good on both sides of the connector, it lowered the probability that the problem was corrosion at the steering wheel harness connection. Next I split the connector at the steering wheel and confirmed that there was not an issue with corrosion. I turned on the headlight switch and confirmed I had good voltage to ground at the red/black wire (low beam circuit). I then connected a jumper wire to the red/black wire in the dash harness and grounded the other end of the wire while monitoring the voltage. The voltage dropped to zero, but the low beams were not illuminated. Thanks to @Captain Obvious, I knew that meant there was corrosion in the circuit obstructing current flow. (As he has mentioned in other threads, voltage readings show potential, but that doesn't mean the path can support the current flow.) I referred to the service manual to find which connector linked the red/black wire from the engine harness to the dash harness. I found it was connector C-2 (see below). (The 260Z and 280Z manuals have great break downs of the lighting circuits in the Body Electrical section.) This connector is located near the firewall in the passenger footwell. I found that the size of the connector would not allow me to backprobe with my full-sized meter probe, so I opted to use the back probe kit I got from Harbor Freight to take a voltage reading at the connector. I inserted the probe on the engine harness side of the connector and operated the headlights. There was still voltage to ground. Since this wire is the path to ground, it should not have voltage. That indicated there was an issue at this connector. I confirmed by connecting the back probe to ground and turned on the headlights. I could see the low beam, so this validated my theory. I opened the connector and found many terminals were green and white from corrosion. Polishing the terminals with a Dremel and wire brush did not remove enough corrosion. Unfortunately the AMP style 1 connectors/pins are no longer available, so the solution was to remove the affected wires, put on 6.3mm open barrel spade terminals, and insert those terminals into a new connector. When I was finding the issue at C-2, my friend noticed that only the passenger headlight illuminated on low beam. We tested the headlight bulb sub harness and confirmed that the other 2 wires at the connector were good. He had another sub harness, so we installed that and confirmed that the issue was with the sub harness. He depinned the low beam terminal from the headlight connector, but I could not see any issue. That left me to believe that the problem was at the connector between the sub harness and engine harness. I depinned the red/black wire from the connector and installed a new terminal on the wire. We re-tested and found that both low and high beams were working.

Have you verified gap and dwell on the points? Have you measured voltage to ground at coil positive with someone else holding the key in START? Also, you may want to check for voltage to ground at the blue arrow with the key in ON and check for resistance to ground at the red arrow (key off or on). The screw at the red arrow should be grounded.

You may need electronic flashers for the turn signals and hazard lights after switching over to LEDs.

Since you say your hazards work, I suggest you focus on the connector between the dash harness and body harness. First verify you have voltage to ground on both sides of the brake switch with the pedal depressed. If so, keep moving down the line. Connector C-2 is most likely good in that case since the wires on both sides of the brake switch go through it. If the connector I circled is together, take it apart and measure voltage to ground on the black/yellow wire on the dash harness side with the pedal depressed. If it's good, put the connector back together and see if you can get your meter probe on the back side of the body harness connector at the black/yellow wire. If you still don't have brake lights when you have voltage at the connector, move down to the connectors at the tail lights and repeat the process.