As advised by Zed head, I'm going to start my own thread to document everything I've troubleshooted while trying to get this car started. This is my first EFI car, and I'm learning as I go, but I believe I've narrowed the problem down to the EFI system.

• The fuel pump is running and generating good pressure within the fuel rail. I have found no leaks or vacuum leaks.

• The AFM (Air Flow Meter) appears to be working; I can see it moving while cranking. I checked the continuity at the ECU pins, and the readings are correct, one pin is slightly higher resistance but looks to be okay. Im not sure if the AFM has a connection that i can take off an clean. looks to be directly wired.

• The starter/injector relay on the driver's side is clicking over and functioning properly.

• I've installed a new ignition coil and verified that there is spark at the spark plugs.

• The car can start with starter fluid but will not continue to run without it.

Beyond this, I am unsure how to check why the injectors aren't getting a signal. I'd like to avoid removing the injectors and disturbing the fuel rail for now. My main question is how to troubleshoot why either the injector relay or the ECU is not sending a signal to the resistors, which in turn should activate the injectors.

I tested the voltage going to the injectors and I'm getting right around one volt or less.

Did you disconnect the Neutronics thing? The EFI computer is sensitive to the tachometer/coil - signal on Pin 1. I see a "Power/Tach" label on the box, implying that it's also connected to Pin 1 or the coil. If the Neutronics box is shorted it could cause a no-start. Plus, there's no guarantee that it ever worked.

Does the tachometer needle move when cranking?

I also see some open vacuum lines in your picture.

https://www.classiczcars.com/forums/topic/69545-1977-280z-ignitionfuel-system-neutronics/#comment-679115

p.s. did you measure voltage across the injector connector pins or from one injector connector pin to ground. The second way is the correct way.

p.s. 2 you're falling in to the "it measured good" trap. We need the numbers.

1 hour ago, Toiletduck34 said:

I checked the continuity at the ECU pins, and the readings are correct, one pin is slightly higher resistance but looks to be okay.

First thing - the AFM does indeed have a wiring connector, it's of Bosch design (as is the entire EFI system in your Z) and it's, like most Bosch connectors of that era, a PITA to remove. If your AFM is in place it will be difficult to see as it's underneath all that.

Second thing - you really need to make sure the injectors are opening. It's sort of easy if you have the right stuff, and can be done in place IF you know how to release and remove the BOSCH injector connectors... If for instance you HAD a spare Bosch injector connector with a pigtail, you could put it on each injector in sequence and use a 9-volt battery to quickly apply and remove voltage to the pigtail wires. Yes, a 9-volt battery will open an injector.

If you hear the distinct CLICK of the injector opening you can immediately rule out the "crapolla, the injector is stuck closed". (here I have to say: one side of the battery needs to be permanently connected, the other (doesn't actually matter which) needs to be loose so you can just tap the exposed wire end to the bare pole quickly. You DO NOT want to hold voltage to the injector except for a very brief period of time - that's how they work, milliseconds...

IF STUCK they in truth need to be pulled and cleaned (and flow balanced) by a professional shop OR replaced - BUT most of the time I can get a stuck injector opening again by rapidly tapping the wire for awhile (several seconds or more) until I hear it clicking. That may help you in your effort to get it running even if things are not all perfect.

The injector is a coil (an electromagnet) so both of those spade connectors are actually tied together by the coil. You should see that when testing with an Ohm Meter - leads placed on the two should show a steady Ohm value. If that circuit is OPEN, the injector is bad and you can't fix it.

Now, you can also test that the injectors are getting voltage - they should ALWAYS show battery voltage if the Ignition switch is in the ON (or Start) position. And, because it's a coil, you WILL see voltage on BOTH sides IF the harness wiring is connected to the injector. If the injector connector has been removed you will see battery voltage ON ONE SIDE of the connector an not the other. The ECU asserts a ground to the other side of the connector to open the injector and, like I said, this happens FAST. You will never see this activity with a meter (oscilloscope yes).

Because they are basically a coil IT DOES NOT MATTER which side gets power and which gets a ground signal. Most people wire the "hot" side consistently to one side of the connectors, BUT they don't have to! There is NO "+" side or "-" side. If there was, the injector would tell you.

7 minutes ago, cgsheen1 said:

If the injector connector has been removed you will see battery voltage ON ONE SIDE of the connector an not the other.

Actually (I think) this only true if all of the injectors are disconnected. It's a parallel circuit for the 280Z EFI. Batch fire injectors. CO pointed that out way back when I mentioned getting voltage on both sides. Or it might be if the injectors on the same transistor are all disconnected (there's two, either 3 + 3 or 4 + 2). The later sequential systems wouldn't do this.

Anyway, I have seen 12 on both sides, which was confusing. But can't remember the conditions under which I was measuring.

There are other tricks to test the injectors and the injector circuits. Like tapping coil negative to ground three times. But, it's best to do the simple stuff first, probably.

UPDATE:
Thank you for that information. I have unplugged everything I could from the Neutronics device, though I'm not sure if it's affecting anything.

However, I've made a big step forward: I can now get the engine running for a short period of time! I don't understand why, but hopefully it makes sense to someone here.

Here's what happened: I decided to clean the cold start sensor. While I was putting it back on, a neighbor came over to talk, and I forgot to tighten the hose clamp that connects to the fuel rail. I started the car, and it ran—but with a fuel leak. If I tighten the clamp back down, it won't start at all.

I checked the fuel return line to ensure it's flowing, and it's fine.

When the engine does run, the RPM is very low. If I increase the throttle to approximately 1500-2000 RPM, it runs perfectly for about 9-10 seconds and then instantly dies. This happens every time without fail.

17 minutes ago, Toiletduck34 said:

tighten the hose clamp that connects to the fuel rail. I started the car, and it ran—but with a fuel leak. If I tighten the clamp back down, it won't start at all.

Which clamp? And where is the fuel leak ending up? Maybe it's getting pulled in to the intake system.

At least you know that you have spark. Does the tachometer show engine RPM when it is running?

5 minutes ago, Zed Head said:

Which clamp? And where is the fuel leak ending up? Maybe it's getting pulled in to the intake system.

At least you know that you have spark. Does the tachometer show engine RPM when it is running?

its not near close enough to get into the intake. I did test the injectors and they are coming up with 12V now. When i tested them i was testing while cranking thinking both sides would be (+, -) but both sides are showing 12v. i can make it leak anywhere on the fuel rail and it seems to work. its really odd. i dont know how the fuel pressure regulator works but maybe i have too much pressure? Ill check the RPMs.

EDIT:

RPMs shows, i can keep revs around 800-1000+ and it runs for 10 seconds then stops every time. I engine has warmed up and I tighened the all the hope clamps so gas isnt leaking out and it still runs. Maybe whatever cobwebs were cleaned out since its been sitting for 10+ years.

will continue to read and troublshoot.

Edited 1 hour ago1 hr by Toiletduck34

Close up any vacuum leaks to the intake system. All air has to pass through the AFM so the computer knows how much fuel to add.

And the big screw with the wide washer head on the throttle body is the idle speed screw. It lets air past the throttle blade. You can adjust it by hand to raise idle speed while you troubleshoot.

I can still learn! Yay?

https://en.wikipedia.org/wiki/Toilet_Duck

Toilet Duck is an American brand name of toilet cleaner noted for the duck-shape of its bottle shaped to assist in dispensing the cleaner under the rim. The design was patented in 1980 by Düring AG from Dällikon, Switzerland.^[2][3] It is now produced by S. C. Johnson & Son.

The Toilet Duck brand can be found in the United States, United Kingdom and other countries around the world. In Germany, it is known as WC-Ente, previously produced by Henkel,^[4] and now by S. C. Johnson (Germany).^[5] In the Netherlands and Flanders it is called "Wc-eend", in France it is sold as "Canard-WC" and in Italy as "Anitra WC". In Hungary it used to have the name "Toalett Kacsa". Meanwhile, in Spain, it is sold as "Pato WC", in Portugal as "WC Pato", and in Mexico, Brazil, Colombia, Argentina and Chile as "Pato Purific" or simply "Pato". In Indonesia, it is one of the "Bebek" (duck) line of products, such as Bebek Kloset, Bebek Semerbak, Bebek Semerbak Flush, Bebek In Tank, and Bebek Kamar Mandi.

Edited 1 hour ago1 hr by Zed Head

How long since a new fuel filter up front on the passenger's side? Sounds awful familiar of a clogged up tank. You can run a hose before the pump to a gas can to bypass the tank as an easy test