Zed Head

You've probably lost vacuum at your vacuum tank. I had a hose that kept splitting at the tank's supply side. Cold air was the sign that it had split again. The mode door is vacuum operated. No vacuum, you're stuck in cold mode. You can see it in the illustration.

Yes, you should try to buy it.

What was the pressure before? And what is it supposed to be for your engine management system? Sorry, again, but there's no "yeah buts" that work. We've all made mistake in how we thought things worked. Best to absorb the new knowledge and move on. You can waste a lot of time trying to make wrong look right. Your statement has a lot of new wrong in it too. Seriously, it does. You might take a step back and ask yourself if the 1991 engine management system you're using is the most effective way to get what you want out of the engine. What you really need is the factory service manual for a car that used that engine. Looks like the Toyota Supra used it. https://en.wikipedia.org/wiki/Toyota_Supra#A70 https://www.amazon.com/Service-service-electrical-diagrams-specifications/dp/B005DGOLW4 Might be more effective to just use Megasquirt.

It's more pleasing to the eye than this one, for sure.

Seriously, I've only surfed some heating oil stuff recently. Or is this welding gear?

I had this same type of problem on a lawnmower. I think the hose delaminated because I had been using starter fluid to start the mower and overspray got on the hose, swelling it. Still, same effect. It would start but lean out and die after a few minutes. Not obvious by eye. Don't forget that the inlet side of the pump is under suction.

Your free-flow test seems to show that the pump flows fine. 25 versus 30. 25gph is a lot of fuel. I don't think anyone here has an engine that could burn that much. If you do decide to get a new pump, I'm with jonbill on the brands. Get an OEM brand, without the hypey name. Most of the old brand names like Holley have been sold and the quality level minimized for profits. You're buying an expensive name on a cheap product. "Sniper"? What does that have to do with cars and fuel? Hype. I didn't read the whole thing either but where is the pump mounted? Was the flow test with it mounted in its normal spot? Position can affect performance.

The key finding is that they are even across all cylinders. Unless you plan to take the engine apart there's not much to gain by measuring again. It's just a number.

Good luck Fast Sarah. You know that it's okay to come back and share some knowledge even if you don't have a Z...

The numbers are so consistent that your test method seems fine. I think that "racing" cams can give lower cylinder pressures because the valves close later, to get more charge in to the cylinder. The gauge hardware can give lower numbers also. The tubular extension that makes it easier to reach the plug hole will give lower numbers for sure. Is it an L28 head or modified L24? You could have dished pistons under a head designed for flat-tops.

Sorry. Not right. It's just not what the O2 sensor produces and not how they're used by the ECU. https://www.autozone.com/repairinfo/common/repairInfoMain.jsp?targetPage=productsHowToInspect&leftNavPage=productsHowTo&pageId= 0996b43f80a01215&subtitle=test http://www.autodiagnosticsandpublishing.com/feature/o2-sensor-testing.html 91 is going to be the simple narrow band sensor. And, 91, just like all of the EFI control systems, needs all of its sensors intact, connected and working correctly. I doubt that it has a limp or fail-safe mode. The engine is just running poorly because the inputs to the system are bad, including ignition timing and fuel pressure probably/maybe. At least it runs though. Good luck.

Consider buying an OBD reader. It will tell you the codes that the computer is generating, which can come from feedback or just damaged components. Some OBD readers can also scan live data. With an app on your phone or a computer program and a USB cable, tou can see the senosr values, and how the computer is respnding. IT's a great diagnostic tool and very educational. I have the BAFX reader, and the Piston Android app. Many other options though. Not sure what year your engine harness is but it's probably OBD-II. https://www.amazon.com/BAFX-Products-Bluetooth-Diagnostic-Scanner/dp/B005NLQAHS

Good luck. They all produce a voltage. https://www.fixdapp.com/blog/oxygen-sensor

I second this also. The 044 is a high volume pump. Known for overpowering fuel lines. The ECU/PCM works on an assumed base fuel pressure. It can only adjust so much.

I cobbled together your basic facts. It's not really clear what you're using for engine management, the ECU and harness. Also looks like you're just connecting things up then seeing what happens. Not a great idea, especially with a turbo engine. Most modern engine management systems have a fail-safe or limp mode to protect the engine when things aren't right. Timing is retarded, and/or cylinders are shut off. Also looks like you're not 100% on the O2 sensors and how they work, and the different types. You need to get the right ones, guessing and getting lucky is iffy. I'd get the pinout for your ECU and wiring harness and spend some time checking every circuit. Adding extra grounds is kind of pointless. There's no magic, just get the right parts connected the right way. Good luck. Looks like it will be a lot of fun when it's running. Be careful too, you'll have enough to be spinning in circles before you know what happened.

I posted a picture of the 77 18:1 below the 76 15.8:1, in my post #13. By "as you found", I meant what you found in the early FSM. I was trying to say that maybe you have an earlier rack, 1976, with the 15.8:1 ratio. 1977 was a change year. I wonder if the gear changes might show up on somebody's parts CD? It's not shown in carpartsmanual.com.

That's a good one. Looks like the last change was 7/73 though. http://www.carpartsmanual.com/datsuns30/Datsun-Z-Index/Axle/Front-Axle

I only looked at the years in question on the rack specs and they are the same by FSM year. But, maybe, as you found, you have a 15:1 (actually 15.8) instead of 18. Here's 1976, and 1977. Maybe you have a 76 rack. I don't feel so wimpy anymore. I assume the higher number is higher mechanical advantage? Not sure.

I made something like jonbill did from an old piece of trailer hitch hardware. Same concept, get a strong piece of metal that will jam in to a tooth. Be aware that Nissan used some pretty strong threadlocker from the factory install. Either that or somebody else did when they worked on mine. If it's never been off those bolts might take some real effort. The bolts should have been torqued to 100 ft-lbs so will need at least that to break free.

Wiggle, wiggle, pull usually works if all of the bolts are out. Grab the tail, work it back and forth and pull. Or push it back in and get some inertia going, it might pop free. They do get stuck, so that's normal. Make sure it's supported. They're heavy.

The pilot bushing and pilot shaft can wear and get stuck. Also the splines on the clutch disc can get crud buildup and/or rust. Did you get the two small bolts on the bottom removed? They attach the dust plate to the trans. Easy to miss they're small, on the bottom, and usually covered in greasy grime.

Tire air pressure? Probably have to swap wheels to be sure it's a car difference and not a tire/wheel difference.

Odds are you'll never find a "kit" for what you're trying to do. If you removed your 77 bumpers and took the car and the 260 bumpers to a shop they could probably get it done for not too much. You could mock it up at home with zip ties and assorted hack stuff to see what it might look like. Take a picture if you like what you get and take that picture to the shop.

Since you have a 73 it's probably a good bet that the carbs and parts are from 73. Doesn't matter that it's an L28. There's a chapter in the FSM called Emission Control Device. Download the FSM and start there. You won't find removal instructions but you can figure out how things work. That's the key. https://www.classiczcars.com/files/

Hey David F I think that you might not be understanding what we're telling you here, and maybe you're not clear on how the early tachometers work. They don't sense voltage, they sense current. A blast of current rushes through the circuit for every spark. The tachometer "senses" it and "counts" it. Current, generally, causes heat. Too much current can cause too much heat. Lower resistance allows more current to flow. That's why the coil's are fairly high resistance on the primary circuit, and why there is a ballast resistor to lower it even further. And that's why the primary circuit resistance is so important. So, the "help" is - measure the primary circuit resistance of both coils and post them up. If they're correct then maybe your tach just died. If they're incorrect, then making them right might get the tach working. Good luck. The part about super conductors was a joke. Your coils do have some resistance, I'm positive. You just need a decent meter and some time to get it.