SteveJ

You could use a Holley red - https://www.holley.com/products/fuel_systems/fuel_pumps_regulators_and_filters/fuel_pumps/carbureted_fuel_pumps/carbureted_electric_fuel_pumps/parts/12-801-1 It would have enough flow. You should monitor the fuel pressure to determine whether or not you need a fuel pressure regulator to reduce the fuel pressure at the carburetors. You will need to mount the pump near the gas tank. The next thing to determine is whether or not the wiring is in place to power the fuel pump. Are you ready for a series of questions?

The mounting is different, too. You have to adapt the 260Z tach internals to the 240Z tach or adapt mounting brackets on the 260Z tach to mount it in the 240Z dash. The 240Z tach has studs on the left and right. The 260Z/280Z tach has a bracket at the bottom and a screw that goes through the top front of the gauge.

The 260Z and 280Z tachometers are interchangeable functionally.

But @kcpope jumpered out the ballast resistor, so maybe a higher impedance coil might help.

Look for vacuum leaks all around your intake.

There's a video for that. How it works on the wiring diagram: https://youtu.be/5eUMImOnfHc

Did you by the OEM version Z Car Depot sells, or did you buy the generic one. I'm pretty sure this is the Nissan part: https://zcardepot.com/products/ignition-switch-oem-240z-260z-280z-510?variant=19275160191089&currency=USD&utm_source=google&utm_medium=cpc&utm_campaign=google%2Bshopping&srsltid=AfmBOopH6VW3h4MxQaEG7pE62G-UpFxLVWe6672qDYb_WLqBrkGVJY-VnhA

Well for the bottom part, reach out to Junkyard Jenny. https://junkyardjenny.com/

https://zcardepot.com/products/door-latch-striker-catch-left-oem-240z-260z-280z-70-76?variant=39520640008305

My first guess would be a check valve issue with the fuel pump if it's a mechanical fuel pump.

Are you saying continuity by a meter tone or by a resistance reading of 0 (or almost zero)? Was the K18 relay plugged in? If not, did you just have the 1 jumper in between BY wires? Was the connector for the ignition switch connected to the switch, or was it off with no wires attached? The bottom line is that the BY wire is never grounded, but you have to make sure of your testing methods/conditions. If you don't control the methods/conditions properly, you can end up going down a rabbit hole. Been there. Done that. Many years ago I lost the fuse for the parking lights/gauge lights. In tracking down the short, I first guessed that it was probably around the gauges, and after unplugging the speedometer, the short went away. My method was flawed as the positive and negative wiring from the speedometer affected all of the gauges downstream. After realizing my mistake (and wasting about an hour or more), I resumed my search with a better methodology only to find that the positive wire for the light by the defroster switch (74 & later) had become detached from the socket. In other words, make sure you aren't shooting yourself in the foot.

You only need to jumper the ones you did to get continuity. Everything else can be left disconnected.

Okay, I had to dig through the 73 wiring diagram. That looks like the K18 relay. If the relay has failed or lost its ground, then the car won't start. That's part of the nag warning for the seat belts. While it's present in the 72, the circuit didn't make it into the wiring diagrams. You can get this connector from Vintage Connections (https://www.vintageconnections.com/products/6-3mm-connectors?variant=46131501236545) and make a nice, plug-in jumper.

First check the jumper. Make sure it's still in place. Next, you want to make sure you have continuity in your wiring harness between the ignition switch connector and the solenoid. You want to make sure the dash harness to engine harness connector is still connected firmly (and free of corrosion). This is the connector you are looking for: You might have to get some help to test the entire length. One way of testing is to take the BY wire off the solenoid and make a jumper wire to ground it. Then see if you have continuity to ground at the ignition switch connector. I cheat. I have long enough leads to test wires from the front to back of my Zs.

Year of car? Was it originally manual or automatic? Please go here and click on the link to create a signature. https://www.classiczcars.com/settings/ Include information such as the year of your car and any known modifications. It helps a lot with troubleshooting.

The key piece of missing information: What is the voltage to ground at the WR wire? If there is no voltage at the WR wire in a 240Z there are two primary causes: The fusible link is bad. The ammeter gauge is bad. Does your horn work? Do your hazard lights work? Do your brake lights work? If the answer to all 3 are "no", then look at the fusible link. Next: If the answer to any of those 3 is "yes", then do you have power at the cigarette lighter? Do your running lights work? Does the inspection light work? If none of those circuits work while you have hazards, horn, or brake lights, then it's quite possible the ammeter gauge is bad. (Note: I have seen a couple of real-life cases where the ammeter gauge blew because someone connected a battery backwards.)

When you get the horns back, look for my video I did on horns. It may aid in reassembly. https://youtu.be/oOHLgH1o-oE?si=Cle_9Ey2BWmjFxZU

The condenser served two purposes. It prevented premature wear on the points (240Z only) and it reduced electrical noise. Electrical noise is really more of a problem for AM radio than a modern FM radio. The ignition system won't even notice if the condenser isn't there.

And I just did a search on FB. Many people in the Georgia Z Club identified it as a scam.

Classic scammer tactics. Move on.

I finally remembered to upload the wiring diagrams from the FSM. There are some errors. The intermittent wiper relay wiring is wrong on the diagram. The 74 manual corrected the errors. I can't recall other errors off the top of my head, but Matthew Abate and I were running across them as he tried to rebuild his wiring harness. 73 Wiring Diagrams.pdf

I don't know if the 71 had the seat belt warning. I think the headlights may have constant voltage with the headlight switch completing the ground path. In the 72 & 73, the headlight switch connected the positive with the fuse box with a red wire. There may be some other differences that I haven't tried to determine.

The funny thing is that many people at work have seen my 260Z since I used to drive it in to go to club meetings immediately after work. A few people asked if I had painted the 260Z thinking the new Z was the 260Z. The two main roads that lead to my neighborhood both have construction going on in different places, so on my commute home, I might take a roundabout way home even if it takes longer so I don't have to sit in traffic. There are also more curves, so that is a plus.

I would still remove the valve cover. If you find signs of scratching on the cam, you can figure it also happened to the bearings on the crank.

To piggyback on @Captain Obvious's reply, look for debris on top of the head and any signs of scratches on the camshaft when you have the valve cover off. Like @Patcon, I was thinking bearings. I've been regularly watching the engine teardowns on the YouTube channel I Do Cars. When I saw the photo, I just heard the host of that channel saying, "Forbidden glitter". That's his phrase for finding the remnants of chewed up bearings. With the pan off, did you happen to check the rods for play?