SteveJ

Make it a 6 pack of Diet Dew. I don't drink alcohol like normal people.

I have a feeling that it's wear on the contacts on the ignition switch allowing bleed over somehow. Maybe I'll run a test at the switch some day.

Oh, so you want a video? Now I'll have to charge you.

I did some testing with the wires swapped. While there should not be voltage at the coil while starting with the wires swapped, I did read a little over nine volts. That may be from slop in the contacts with a switch that is almost 50 years old. I also pulled the negative off of the battery and checked resistance between the black/white for ignition and the positive post of the battery. At first it was just a couple of ohms with the key in ON and about 50 ohms with the key in START. However, I noticed some fluctuation in the readings with the resistance with the key in ON increasing when I released the key from START. That is why I think there could be some slop in the switch. However, I was not seeing any continuity between the black/white wires no matter what position the key was in. I'll test some more later.

That is called a hinge. I can take some photos later today.

I will verify this evening. It will only take a few seconds with a meter. I still have my doubts about being able to start the car with the black/white wires swapped.

Yes, I have my doubts about the swapping of the wires. I'll have to test that this weekend. Anyway, I believe the OP has his car wired correctly, so I hope he didn't swap wires.

It's one of the most rust-free cars you'll find outside of the southwest US, but the frame rails have been beaten up completely from idiots using them as jacking points. The funny thing is that I set the valve lash, changed the oil and balanced the carburetors before the seller bought the car. And I got advice on setting the carbs at high RPM from the person the seller hired to set the valve lash, change the oil and balance the carburetors. The only thing he didn't mention is setting the dwell, which I did as well.

Here is one that personally worked on. I know the seller and previous owner. https://bringatrailer.com/listing/1971-datsun-240z-179/

When you did the continuity measurement, was the tach plugged in?

You missed a key detail in my video. I said ALL the wires were disconnected. You had the ignition wire connected to the ballast resistor along with the green/white wire. That's why you had voltage on the black/white at coil positive. Anyway, all the wires are connected properly. Post a photo of the back of the tach if it's still out. Let's make sure it's a 240Z tach. It would take some rewiring to mate a later tach to a 240Z, but with the other surprises on your car, we don't know what we're going to find.

You are correct about it not looking stock. It looks more like a 260Z housing. (I just went down to the garage to look.) For reference my 73 does not have that fitting, but my 74 does. @Captain Obviousmay have the size memorized. It could be a BSP fitting. Anyway, the fitting is for the water temperature switch for the 260Z EGR control. If you are really curious, see page EC-16 in the 74 FSM. The switch is still on my 74, doing nothing. When I needed to install a coolant temp sensor for the fuel injection I put on that car, I used the fitting on the side marked below. It's 1/2inch BSP. I found the right size BSP to NPT adapter for the coolant temp sensor. The 74 already had the coolant hoses removed from the carburetors. I plan to remove the coolant hoses from my 73 soon. I just have a BSPP plug for the side fitting. I bought an elbow fitting from Napa to replace the three-way coolant pipe on the passenger side of the block.

Load test the battery to make sure it is good. Make sure the battery is fully charged. Download the FSM if you don't already have a copy. Focus on the EE section. Use an ammeter (not the gauge) to look for any drains on the battery. Hint: unplug the voltage regulator to see if that kills a drain. Test the charging system components, using the FSM as a guide. Make sure you are making notes on what & how you test with the readings/results so you can share with us along with details of what you have worked on/modified. If you're not sure of how the charging system works, then I would advise against modifying the wiring. Especially with the 260Z, if you don't know what you're doing, you'll quickly wind up with a car that does not start.

It could be the voltage regulator. Also, make sure you charge the battery fully. Running the car with a battery that is too weak/low can damage the alternator. Do you know how to use a voltmeter? You may also need to use an ammeter. This type can be helpful if you learn how to use it. https://www.amazon.com/Current-Auto-Ranging-Digital-Ammeter-V-Alert/dp/B094R8CB4W Until you can take some measurements and diagnose, you're just throwing parts at the problem. While you may be able to solve it that way, it tends to be more expensive. Also, following what @Zed Headsaid, go to Account Settings (Click on the dropdown at your username if you're using a computer to access this site.) and then go to Signature. Put your car information in the signature. That will help people know what car you are working on. There are wiring differences between the years.

I believe RockAuto will ship to Mexico. In the US, they are usually cheaper than the parts stores. Anyway, if you are still using points, you need the ballast resistor, or you will burn up your points. Depending upon the voltage you need for the electronic ignition, you will probably bypass the ballast resistor later. Ballast Resistor: https://www.rockauto.com/en/catalog/nissan,1972,240z,2.4l+l6,1209169,ignition,ballast+resistor,7052 (Helpful hint, if it comes with a jumper wire like what is shown on the photos of the resistors, throw the wire away.) Ignition Coil: https://www.rockauto.com/en/catalog/nissan,1972,240z,2.4l+l6,1209169,ignition,ignition+coil,7060 This coil has the same specs as the one you saw on the Autozone site: https://www.rockauto.com/en/moreinfo.php?pk=931800&cc=1209169&pt=7060&jsn=1758

Motor Trend listed the color choices. I hope you like 2-tone. https://www.motortrend.com/news/2023-nissan-z-trim-comparison-sport-vs-performance/

Based on a hint from Chris Karl, I figured it would be called Z. Am I the only one who felt they cut the reveal short? They could have shown us more details of the car.

If he can't, I can.

I hope this clears up some confusion about which wire goes where.

That's the high/low beam selector. Two wires return from the headlights, and this switch will connect one of them to ground.

I'll see about shooting a short video after I'm done with work today.

No black/white wire goes to the negative on the coil.

This evening was a short one. I replaced the sealing washers on the banjo fitting of the rear carb. After cranking the starter to run the fuel pump, I verified that it had no leaks, but then I noticed a little fuel on top of the float bowl on the front carb. After changing out the same washers on the front carb, I was ready for an attempt to balance the carburetors. I started with both at 2.5 turns down. I got the engine warm and checked the engine speed. It was about 650 RPM. I bumped up the idle screws and balanced the carburetors with an idle of 750. I then held the engine around 1000 RPM. The back carburetor was pulling according to my air flow meter, but the front didn't budge. I fiddled with the balance screw and a few other things, but nothing changed. I called a Z friend, and we went through a few things and decided that I should test the front damper. Just as I was about to hang up the phone, I noticed that the vacuum advance was still unplugged from when I was getting it out of the way earlier. Oops. Well, with the vacuum leak gone, the front carb seemed to respond MUCH better.

The white/red wire in the dash harness should have a female connector with soft plastic insulation over it to keep from shorting against the body. It connects to the male connector on the white/red wire that is attached to the switch. The red wire in the dash harness should have a male bullet connector that fits in the female connector on the red wire on the switch. The female connector again should have soft plastic insulation to protect it from shorting.