Zed Head

Yes, move it down to the return line. You should not get much pressure at all after the FPR but if you do that means you have a restriction back toward the tank on the return line. When you have it off just eyeball the size of the hole in the T. If it's comparable to the hose it's not going to be the problem. You should be able to see right through the T fitting.

Also, is there any chance that your gauge is causing a restriction? Where is located? If the adapter "T" is small diameter is might cause a problem.

The damper should be on the inlet side so would not cause higher pressure. Maybe somebody plumbed it in to the return line? It looks like you have a restriction in the lines somewhere after the gauge. Try moving the gauge to the return line, in the engine bay. If the pressure stays high that means the restriction is between the engine bay and the tank. If the pressure drops that means the restriction is between where you had the gauge before and where it is in the second location. You need to find the restriction to get the pressure corrected. Pump > damper > filter.

Good luck. You're way off spec.

You might be able to get a generic replacement. Those types of seal are sized by inner diameter, outer diameter and thickness. I took an old seal to a bearing house and they had no problem finding a generic part. Here's an example of the huge number out there. https://www.powerindustries.com/catalogs/US_Seal_Mfg_Catalog_2012.pdf

Cut your own is probably your best option, or use a light coat of RTV. Some people say that their bars don't have any gasket. We've rambled on about them in the past...

A little compressed air shouldn't hurt anything. You can probably knock some of that dent out with a broomstick too. I would do as much testing as possible before dropping the tank. You don't know what the root cause is. You could put it all back together and be in the same spot.

My mistake, they don't need to be high pressure. They should be fuel rated though. I don't know if automatic transmission fluid hose will swell in the presence of gasoline. The one on the other side of the fuel pump needs to be high pressure EFI hose though. I've found that when people start using the wrong hose in one place they tend to do it in many places.

SAEJ1532 is transmission fluid hose. I would do that flow test in the engine bay, get your numbers written down so you can study them, then maybe tear your system down and get the right hoses on it. https://www.sae.org/standards/content/j1532_200503/

I would disconnect it in the engine bay by the filter. It's easier to access and get a container in there. A clear two liter bottle would work well. Plus you can watch the gauge. You'll have flow and pressure right in front of you. Are those hoses high pressure EFI rated? You should check. They might be splitting internally. Even the return line could be failing. You can still run the pump and report pressure before you do anything. Ideally you get all of your measurements at the same point in time. You have your pump voltage and weird fuel flow above, but no pressure readings.

You should get a constant flow. Pretty strong too. If you want to be sure, remove the return hose and put it in a container, then run the pump again. You have odd things happening with your fuel supply. Maybe your fuel pressure regulator (FPR) has foreign material in it. Your pressure fluctuates from too high to too low. You might have crud in it blocking the outlet, raising pressure, then holding it open lowering pressure. Who knows. Let the pump run like you just did and report the fuel pressure. Sorry for the weird quotes. Turns out you can only "multi-quote" from one page at a time. Not the whole thread.

The description you copied is for a diff fluid. Maybe you were on a multiple item page. Forgot to say the "10-4014" part number got me here. Here's a few links. That Scoggins Dickey price looks good, I might buy some. Watch out for shipping costs. https://sdparts.com//i-24093516-acdelco-friction-modified-synchromesh-transmission-fluid-1-qt-10-4014.html?gclid=EAIaIQobChMIyMf-nYfb4AIVkxx9Ch2ZJA0HEAQYASABEgKnX_D_BwE https://www.summitracing.com/parts/ado-10-4014 https://www.amazon.com/ACDelco-10-4014-Friction-Synchromesh-Transmission/dp/B0026JK8FK

Different for automatic transmissions, same for manual. The chart is manual, M/T, on the left, auto, A/T, right. I think any differences are tiny and probably tied to emissions. I've tried 75, 76, and 78 in my car and they all worked the same.

I'm using Synchromesh in a Ford transmission and it's good stuff. I've been thinking about using the Friction-modified for a little more. It's a notoriously notchy transmission. The Ford spec. Mercon V was terrible compared to the Synchromesh.

Maybe it's between 5 and 6, about here.

I missed that and I was looking right at it. Maybe an E88 head then? The block is still N42. The stamp on the #6 cylinder will tell displacement. Might be an L24 or L26. Sorry AChev, we have confused your sale. The stamp on the #6 cylinder will tell much.

One key is to know what you're trying to fix. High RPM synchro problems and notchiness are different things. Many people use plain old 75-90w and do fine, while saving some money. If you want to get fancy use Swepco 201 and ATF at a 3:1 ratio. I use it on my old worn ZX 5 speed and it fixed all of my problems. That's a JMortensen suggestion, except he mixes at 1:1 I think.

Nissan's own ECU document says that the Federal models use the same ECU for the manual transmission cars, even some auto cars. The document is in the Downloads area.

It has the N42 head and N42 block, so probably dished pistons. 75-76 engine. You might pop the valve cover and get a shot of the camshaft. Probably help your sale. Good luck.

Pennzoil Synchromesh is popular. Chickenman and others around the internet say that Friction-Modified Synchromesh is good also.

I think that the valve can get stuck open too. That would have an effect. You might just take the bolts out, lift it off and inspect it like 246 says, then make a temporary block-off plate if it's intact inside. Beware, the bolts tend to break.

If you know someone else with a 280Z maybe they'll let you put yours in to their car. If the problem follows the ECU there's your answer. People have been known to actually see the defects in their ECU's. Burnt parts or cracked solder joints. Might be worthwhile to remove yours and take it apart. It's very easy to do.

One of these - http://datsunforum.com/efi-troubleshooting-kent-moore-j25400-analyzer/

This is another sign that something's wrong in the ECU, I think. Most engines will go full rich, maximum temperature-based fuel enrichment, and die immediately if you disconnect the sensor. If you can find a spare ECU it would be worth a try. Maybe you can borrow one.

So at 4 minutes it died, then you got out and disconnected the coolant temperature sensor to restart it, then you reconnected the sensor and drove away? This is a stretch but it sounds like it might be related to the ECU, at the coolant temperature circuit. The ECU failures lead to either running rich and dying or just plain immediate dying. Disconnecting the sensor stops current flow through that circuit in the ECU. I wonder if that's the basic reason the ECU's die, the coolant sensor circuit goes bad. I had a 78 ECU go bad, and it would restart also after it died. If you wanted to try a weird experiment that might even keep you going for a little while, put a switch in the coolant sensor circuit. Just run a long wire in to the cabin from each side of the bullet connectors and install a switch. It could even be a momentary push button switch. Then you can break the circuit as soon as it starts to die instead of stopping, getting out, and disconnecting it under the hood. It might help you keep going and offer a clue to the real problem. It sounded pretty good until it crapped out.