Zed Head

There's a gauge on the adjustable FPR. Watch the gauge after you prop open the throttle blade so that the engine will stay running. Once the engine is running, many things can be learned and understood. Fuel pressure, ignition timing, throttle response. vacuum leaks, etc.

You should read the Engine Fuel chapter in the FSM so that you understand how things work. And, for whatever reason, you don't use the advice you get and do something completely different instead. Nothing wrong with experimenting but people will lose interest if their advice is ignored. Good luck.

I forgot a bunch about what you were doing. I see also that you already had the idle screw opened up. There are other possible reasons why it won't run unless it gets lots of air. Maybe there is a big vacuum leak and you need more AFM vane movement to supply more fuel. You could test that by propping open the AFM vane. Maybe ignition timing is off. Maybe valve timing is off. If it was mine I'd probably prop open the throttle blade after I got it started, or before I started it, so I could keep it idling while I messed around with ignition timing and the AFM. Either have a friend hold the throttle open or prop it open na dbready to shut the key off it starts to rev too high. Once you get it to idle so that you can work in the engine bay then you can move the AFM vane more or less open to add more or less fuel through the injectors. The effect will be a clue. Actually, if it was mine I would take the valve cover off and verify cam timing, then adjust valve lash, then set ignition timing as close as possible, check the air flow path including the filter for obstructions (mice, etc.), then start it, let it idle, and start fine tuning. Lots of ways forward.

FAIL! Didn't mention hot or cold.

Ask it something technical, like how to adjust valve lash on a Datsun engine. Or change a tire.

If the vane (blade) was stuck open there would be too much air and the einge would rev too high at idle. The whole point of the blade is to keep the air out so the engine does not blow itself up. If you can keep it running with your foot on the throttle pedal (it's called a throttle because it throttles the air from the engine) then you should be able to keep it running by opening up the idle speed screw. Once you get it to idle you can mess around with timing and the AFM vane and other things. You mentioned the AFM and it sounded like you thought that somebody had messed with it. Removed the glue blobs maybe, and adjust the spring tension. That would be bad.

Actually... it is bad. Bland. It leaves me empty, devoid of emotion. Not bad for a grade schooler though. And, 240Z's aren't known for power or roaring. The AI being must have scavenged from Hybridz.

You can re-mark the damper pulley since you're using a piston stop to determine TDC. A 78 should have the degree marks on the tab on the cover. Make a new mark and then you can use a timing light to set timing. Assuming that somebody just put a damper from a different model on the engine. If the damper rubber is bad then it might just move again. Anyway, that's kind of how working on the EFI engines goes. A long list of small things that need to be corrected. Once you get them all correct it will run like a top.

Maybe I didn't understand what you were saying here. Did you assume that the piston was at TDC because the rotor was pointing at spark lead #1? Or did you use a piston stop or at least something in the spark plug hole to determine TDC? The spark jumps across a gap as it gets close to the terminal so you can't really use the rotor to guess at timing. The leading edge of the rotor terminal is what you would want to look at if you're going to guess.

Racer X has a good point. You have so many different issues though it's hard to figure out where to start. On the EFI throttle bodies there is a screw with a big round head on it that you can turn by hand. That is the throttle blade bypass screw that controls idle speed through air supply control. You could try just opening that up, (unscrewing it to let more air in), and see if that will allow you to start the engine and let it run by itself. On the EFI engines there is also the auxiliary air regulator (AAR) that lets air past the throttle blade when the engine is cold. On a properly set up system the AAR keeps the idle up when cold, and the idle speed screw determines warm idle RPM. If you know that the piston is at TDC then the mark on the damper pulley should be at zero. If it's not you might have a bad damper. The rubber degrades and the pulley slips. So a timing light won't help you if that is the case. I'll circle the two parts I mentioned from your pictures and you can check them out. Idle speed bypass screw - AAR -

Is the T plug at the alternator plugged in? Check for continuity to ground through the bottom leg of the T on the alternator pins if it is. The alternator is the ground for the two circuits.

I've heard it as GIGO. Garbage in, garbage out. When I think of "shite out" it starts with food. AI plus the Google ad algorithm will be when things get really bad. Artificial people talking about crap you really don't care about. Can't wait!

There is a fuse that is on the supply wire to the charge lamp circuit. Seems like the most likely place to start. Does the Brake light light up when you turn the key on? That is the other part of the circuit. Don't forget to check your grounds too.

Weird that you said Amp light and not Voltmeter. USA cars from 1976 on had Voltmeters, not Ammeters. Maybe you meant the Charge lamp in the Voltmeter. Is it a USA market car? You didn't say if it has EFI or not either. The more details the better. Maybe @EuroDat is out there and can help out in Dutch, if it makes a difference. No offense intended.

Is it a 1975 280Z? Is it fuel-injected? It could be the power supply to the ECU. There is a ground wire and a power wire, both at the battery terminals. The power wire has its own fusible link. Don't get them backward.

Did things work correctly before? Supply some history of the vehicle. What is it? Did you disconnect the battery before doing the work?

Found it. This is from the 1982 FSM.

The AC belt idler pulley bearings are known to go bad. AC compressor clutch is a possibility. If you have AC. Your video was pretty short. Couldn't tell if it happened on every rev or only the start up. Seems to be starting on just a few cylinders too. Thumpa thumpa thumpa...

I thought that there was a flashing light involved on the ECU somewhere. Vague memory. Might be mentioned in the FSM troubleshooting section.

The auto parts store refrigerant cans are a gamble. I'd take it to a pro. Or at least buy the proper gauges, high side and low side so you know what's what. https://www.amazon.com/Orion-Motor-Tech-Conditioning-Maintenance/dp/B08V5JWJSB/

The pump power probably doesn't matter at Start since the bowls should be full.

The test is best done with all of the plugs out so that you get good engine speed from the starter. If you have a slow cranking speed you'll get lower numbers.

His problem seems to be oil-fouling of the #4 spark plug. And maybe #6. His pressure numbers don't show that #4 is different from any of the others. #3 and #4 are 19% higher than #1, which is at 73 psi. But #1 spark plug and cylinder work okay, apparently. #1 plug actually looks very clean in his picture above. Not sure that anything will become obvious anytime soon. Cylinder #4 has the highest pressure of all, along with #3.

jalex should put the engine specifications in his signature. Carbs, ignition system, etc. Can't remember the details. A multi-spark ignition system might help for something like this. MSD. Cheaper than an engine rebuild. The low cylinder pressures could also be caused by an adapter on the gauge. But those are very low, as stated. I think that I used an adapter once and got 125 instead of 175. 80 psi is waaaaay low. I thought the numbers were higher, in past posts. If those numbers were found with a good gauge on anybody's factory stock engine you'd say that the engine was worn out and needed a rebuild.

Have you examined the voltage regulator? Just to be sure that nobody has messed with the wiring. It should be under/inside that shelf that the fusible links blocks are attached to, protected. A small metal box.