Zed Head

No offense, but once you understand how they work they're not bad when properly installed. Your case sounds like poor installation. It's not the thread insert itself, it's the way it was installed. So, you're right, it was a "half fix" but it's a very common fix. That's why they didn't tell you, probably. You might find thread inserts in some of the other holes that didn't leak. Wouldn't be surprising to find them in the Posi-Quiet calipers either. "Original equipment" just means it started on a Nissan, before they rebuilt it. They didn't cast and machine their own calipers. Notice that they show new pistons, but not new calipers. Better check. Sorry. I'm a bubble buster.

How does it "ruin" it? Might be a clue. But, if you just don't like helicoils, or any repairs at all, it doesn't really matter. Helicoils are just normal repair for any screwed up threaded hole. Screwed up threads are common, that's why "helicoil" is a well-known word of the trades. The other thread insert guys probably hate that. https://www.google.com/search?q=helicoil+definition&spell=1&sa=X&ved=0ahUKEwj2irG9h8nZAhVC3WMKHXvqAPUQBQgkKAA&biw=1496&bih=727

No need to run a jumper wire to the coil if you already have this. As SteveJ said, just make sure you also have it at Start. Stand your meter up where you can see it or have somebody turn the key for you. Not sure that you're thinking through the things that happen when you turn the key. 12.3 isn't a very well-charged battery. If you have a charger you might top it off.

The Scarab 240Z's are unusual and of higher value than the common 240Z to many people. Especially if they were built by the guy that designed them (I think that's the guy, right, Brian Morrow?). Here's a link - http://www.zhome.com/rnt/v8.html

Might be that you actually have two problems. Have you tried starting fluid? If you have power at the coil and still no start, check for spark. If you have no spark consider the igntion module.

He only has two posts. And I think his avatar is a Porsche. Maybe he was being ironic.

I've read about the drive gear slipping on the shaft. It's not common though. Doesn't look like you're actually measuring and there are other things that could be wrong. Seems like verifying where things are at would be easier than dropping the oil pump and moving the drive gear over a tooth. That's what you'll have to do to get more adjustment. I was just describing how the distributor drive works, above. It's not like a Chevy or Mopar where you just lift the distributor up and re- "stab" it a tooth over. It only fits one way, in one position. Good luck.

If there is power to the coil and the engine turns over it should start or at least pop a few times, assuming that everything else is right. But, I think that you need to tell us the whole story of the car. You're starting in the middle and there are many things that could be wrong. You could spend weeks on here, giving small details, when there is something simple that will solve the problem. Tell us a story. It's not clear that the engine has ever even run one time.

Stumbling and popping back through the intake manifold at low to mid-range throttle openings.

It can't be a "tooth off" unless you removed the oil pump. Or you have a US V8 engine installed. The Datsun distributors use a slot and a tang to tie the distributor shaft to the drive shaft. It can only install one way. Just curious, but what timing are you running now? What's the light say?

Patcon makes an excellent point. There is definitely a few degrees of extra on the other adjustment. I dinked around with mine when I was trying to clock my rotor for better centering over the electrodes, when I was trying to run more advance. Funny though, eventually I got tired of trying to squeeze out a few more HP fractions and set everything pretty much back to stock. The FSM shows it with the bolt still in it. You can't see it from the top. I marked the slot that you can see also.

It doesn't look like you've done much testing besides turning the key and listening and looking. And you said "intermittent" which would mean that sometimes it starts normally. That suggests a bad connection or a stuck relay. Best to get a meter or test light and see where the power is, and where it isn't.

There are other ways to get a "tad" more. You could file the slot open a tad more. Nobody can really answer a should question. Should is in the brain of the doer.

Is it an automatic or a manual transmission? Automatics have an inhibitor relay.

Can you give a description of what happens when you turn the key? What happens at On, at Start, etc. You haven't supplied much besides the fat that you're bypassing the ignition relay. Could be that that relay is bad. Here's a picture of mine. My car had a wire run all the way to the ignition switch.

I'm not 100% on that. The clip sits in the cap groove and I can't tell how much sticks out. The picture I looked at seemed to have a small edge available. My point was that if there was a force causing the clip to rotate in the groove that the tips might get levered out as it rotated. Like you do when you're removing them. Took a second browse and found another picture that doesn't look 100% either. Maybe a powder coat buildup? I don't know. The clips don't seem to fit the groove super-tightly. Probably not a problem. Makes me feel funny but I'd still run them. Edit - the Nissan parts are just so precisely done that they make everything else look "bad". Color-coded super-precise u-joint clip fitting procedures and all that. Probably why last 200,000 miles.

I vaguely remember conversations about the CSV pins in the ECU. I think that we decided that Nissan had made some undocumented changes. Many of the ECUs are missing quite a few pins that the wiring diagram shows they should have. The EFI and Fuel Pump relays were split but I'm not sure the ECU actually doesn't anything with them. Here's an old thread. Found it on Google and it's one of those vague memories. Looks like CO had some firm thoughts on it. Nissan developed an analyzer that plugged in to the ECU connector. In 78 they did identify AFM pins that had no function though, so don't know why they couldn't add a comment about those pins if they were for the analyzer. I could see, maybe, a BCDD difference between automatic and manual. Or the fuel cut function, which is controlled by the ECU. But, worst case, I think that something just works slightly differently, probably an emissions function. EFI, generally, was developed for emissions purposes anyway, to start. It's primary purpose.

If you cruise across the Nevada desert at 100 mph in summer heat could cause expansion. The clips are a good backup. You must have jinxed yourself when you posted about how "smooth" things went on the first one.

I think that they call those test lights "noid" lights. Not sure why. I've seen them with two prongs that you can just plug right in to a two wire plug. Any auto parts store would have them. The ECU swap would be a quick easy test. When my 1978 ECU died, it just died completely. I popped in at my house, started the engine, and took off down the rode to give it a run, and the engine coughed once and died about a half mile away. It restarted and I turned around to get back home. It died 2 or 3 more times then wouldn't restart. I was close enough to jog home and get the original to put back in. I'm not suggesting the the switch from 76 to 78 caused it to die. I replaced a part in the 78 ECU and it worked fine after that. Might be why the car sat for 10 years then was sold for parts. I bought it for $300 from a guy who couldn't keep it running. I've had several different numbers in my 76 since then. Maybe I'll pull the box down and list them. Here's an example of the light. But, you can make them from Christmas tree bulbs also, the small ones with two wires. Haven't done it but I've heard about it. FastWoman wrote about them. https://www.oreillyauto.com/search/1977/chevrolet/camaro?q=noid

If the clip is pushed around the slot, like it typically does over and over again when you're trying to remove one, does it hang anywhere? Doesn't seem like there's much driving force to pry it off otherwise. If you mentally/calculate the loads on the caps, they are in to the parts of the yoke that aren't cut away, rotational loads under acceleration. The clips just need to be as strong as the six weak stakes, to keep the caps from pushing out under centrifugal force. Looks sketchy at first glance but big-picture seems okay. A good thought experiment. I mentioned my early experiences with u-joints. They use a strap with a small nut and washer on the ends. All it does is pull the caps in to the seat on the flange. When you look at it it looks very weak. But somehow it holds up. Found a couple of examples.

Pretty sure I've used both of those ECU numbers on my car with no problems. 1976 4 speed coupe. I've collected several over the years and run them for a while to be sure that they work. I have a spare behind the driver's seat, ever since one failed on a test drive. But the ECU is at the end of the line for injector power. So until you confirm power to the injectors, you won't know what the ECU is doing. The relay controls power to the injectors, and the ECU lets it pass through.

Make sure that this ground has low resistance to the battery's negative terminal.

Those power readings are all correct. Your wiring to the EFI relay looks right. Should have power to the injector plugs with the key On. Like Dave said the dropping resistors are in a pocket underneath the windshield washer bottle, by the brake system. You'll have to remove the bottle to get in there. They don't really go bad though. Eyeball them and make sure they're plugged in. OR unplug them and check for power. Also, make sure that you had a good ground point when you were measuring power at the injector plug. And also, somebody (maybe it was you, I can't keep up) just had a problem with the ground on top of the intake manifold. It wasn't good. It's in one of your intake manifold pictures.

Is that with the key On? That's a good test of your EFI fusible link. You should have had power at 73 also. I think that fusible link is the Ign fusible link. It powers your ignition switch. Looks like you either have no power to the switch or the to 73 is broken. Here's a link to a bigger diagram. This progress, although it probably doesn't feel like it. The diagram might be hard to follow. But it shows that 73 gets its power through a path that goes through a couple of connectors, and also branches off to the ignition relay. But it starts at the fusible link. Might be that your Ign fusible link is blown and the source of many of your problems. Recheck the fusible links. ( p.s. Even with carbs you need the Ign link ). http://www.classiczcars.com/files/category/1-wiring-diagrams/

Here's a wiring diagram. Check your dropping resistors also. That's where the power goes right after it leaves the relays. You never what someone might have unplugged in the past.