Zed Head

Looks like the dimensions are the same, but the drain pet-ckok is in a different spot. Pulled out a 76 and an 82. https://www.rockauto.com/en/catalog/nissan,1976,280z,2.8l+l6,1209226,cooling+system,radiator,2172 https://www.rockauto.com/en/catalog/nissan,1982,280zx,2.8l+l6,1209350,cooling+system,radiator,2172 https://www.rockauto.com/en/moreinfo.php?pk=10332348&cc=1209226&pt=2172&jsn=384 https://www.rockauto.com/en/moreinfo.php?pk=10332540&cc=1209350&pt=2172&jsn=391

Somewhere out there, either in the FSM or the Owners Manual there is direction by Nissan that the pump might need to be primed if you run out of fuel. I took a look at what I have but couldn't find it, but I'm sure that I've seen it. I remember worrying about it when I ran out of gas on my 78 parts car. But it had an aftermarket pump and fired right up after I put a couple of gallons in. I assumed at the time that that the OEM pumps must be different.

What pump is it? Brand and model.

Where's the unboxing video...

Sounds like your AFM is not connected, electrically. Might be that the connector/plug fell off of the bottom. It happens. You can can check via the pins at the ECU connector to be sure.

I looked around a little bit and it seems like the manufacturers generally went to computer control of a simple fuel pump relay instead of integrating the timer. But it is a hot topic, so of course, people have filled the need. https://www.ebay.com/itm/174274213748?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=NmzUBVTDRzy&sssrc=2047675&ssuid=bBzFtXzvTQO&widget_ver=artemis&media=COPY This on Amazon, below. The words in search should find it. I don't like to copy their links they seem full of extra stuff. Could probably be made to work.

Define long-term. Hey, you're having fun. Just keep going. There's probably a fuel pump relay out there somewhere with an integral timer. Or try that timer thing in your first post. My 2003 Ford has a timed prime but I think it's controlled by the PCM (aka ECU/computer). EFI is all about emissions so the manufacturers went to great lengths to get everything perfect from the first crank. Have you measured the leak down rate on your system?

My good FPR's (edit - and fuel pump check valve) would hold about 20 psi for days. The bad ones would leak down to zero. Carry on.

I hope it's not so but that sounds little bit like a bad ECU. When it's running poorly do you smell raw fuel from the exhaust? One test/fix that people do is to bang on the side of it while it's acting up. There can be broken solder joints inside that lose connection. A few kicks or knuckle raps can remake the connection. It's not a permanent fix but it's a clue. Could also be the ignition module. The clue there is the tachometer needle. Does it jump around or read higher than it seems it should?

Didn't you check fuel pressure using a temporary gauge in the past? And it was correct? If it was mine, I'd pop the cover off of the AFM and make sure the vane is moving with air flow. Simple stuff, no tools required. Any chance you could summarize everything you've done so far with measurement numbers ? Too many pages to go back and read through them all. I see suggestions that I'm pretty sure have already been made. Plus your problem is different now. The title says "when hot" but now it's when cold. The main problem has changed.

The forum's search engine is terrible, if you've been trying to find things using it. Go straight to Google to get better results. I know that Fastwoman had discussed it in the past. It's not hands-free but it's close. https://www.google.com/search?q=site%3Aclassiczcars.com+fastwoman+momentary+fuel+pump