Zed Head

Seems like the CA ECU would have a unique part number. Maybe @chaseincats could share his and compare it to yours. If you wanted to consider that possibility and for anyone who can't take the time to open their ECU. Seems like it must have its own identifier. One possibility would be to create a device that alters the temperature sensor signal. A resistor inline is the simple way to add fuel by making it look colder. I wonder if one of today's microcomputers could be used to take the real signal and make it look hotter to the old analog ECU.

I wrote a bunch of words but I could have just said put a bigger filter back there. Like this one.

The engine only needs about 1/2 of what the original pump produced, ~30 GPH, to produce maximum horsepower of 150. At 40 HP it only needs 4 GPH. So the engine could run just fine while the pump is slowly losing rate as it tries to push through the filter. https://deatschwerks.com/pages/fuel-pump-calculator So, what are you finding in the filter? Have you cut one open?

Not clear what part with which you disagree. I'm suggesting that the filter is restricting flow causing the pump to fail early.

Do you mean the filters are getting clogged? I think that makes the pump work harder, electrically, and might even cause cavitation, which can wear things out faster. It might even do that before getting clogged, I think that those filters are designed for carburetor flow rates. I've had the thought that if I had a dirty fuel tank but didn't want to replace it or clean it that I would use a larger filter with a high flow rate between the tank and pump inlet. I'd probably look at using a filter like the one in the engine bay. I don't know if it's a high flow filter if used on a low pressure side though. Easy to test though, just fill it up and see how fast it drains.

Be careful with the AI. It's a GIGO tool, collecting, combining, and summarizing all of the garbage along with all of the valuable stuff, like some sort of information stew that also has all of the scraps in the pot. The results it provides are inherently contaminated. And it makes your brain weaker if you don't analyze the results. No offense intended. AI is just a turbocharged search engine. Really, a person should never repeat an AI summary. They should only click through to see where the agent got the results. You'll be surprised at the turds that AI will find and polish and present as "intelligence".

I would just go directly to the potentiometer. It's simpler and more precise, I'd guess, than adjusting the spring. Plus, adjusting the spring doesn't increase fuel at full AFM vane opening. It just lets the vane get there faster. Good idea on using the AFM to richen things up. I'd forgotten about that. I did notice that your idle RPM is lower than spec but it probably doesn't matter much. The automatic is at 700, but it's in Drive, under load.

You could even leave the cover off and run some jumpers to the pins. They are labeled on the inside.

Here's a good thread about ECU's and their pins. CO describes pins to nowhere at the bottom of the first page. https://www.classiczcars.com/forums/topic/60678-what-are-the-facts-about-280z-ecu-compatibility-and-differences/

If I was trying this I would use the wires on the back of the connector, if they are there, and use a switch or manually connect and disconnect the bare wire ends, to see if there is an effect while the engine is running. I'd guess you would hear a change at idle RPM. I might also take the cover off of the ECU first and see if the two terminals are connected to the circuit board. If not, there's no point. These old analog computers don't really have programming (except for maybe that one chip that has come up in discussion in the past), they have circuit schematics that are implemented in the ECU. You get whatever they soldered on to the board. If you don't have a functional CA ECU you might be able to find one out here somewhere. Interesting project, good luck.

Is your distributor vacuum advance connected to ported vacuum on the throttle body? And is the valve at the carbon canister also connected to ported vacuum, with an intact valve? The carbon canister could be a hidden vacuum leak.

There's probably some sort of physics fluid dynamics explanation but I don't know it (viscosity and flow? air is low viscosity compared to gasoline. Nerd 🤢). Since your original problem was a cracked diaphragm, and since most of these old EFI systems seem to run lean for whatever reason, you might be better off with that extra two psi, if it's real. If it starts well and runs well maybe just keep that problem in the back of your mind while you get the car back on the road. It looks like it's now just a distraction. Although, there is still the question of which gauge is correct...

Go here, click "Start new topic" and start your own thread - https://www.classiczcars.com/forums/forum/27-fuel-injection/ Then go here and download the 1980 EFI book. It has all years from 1975 through 1980. Go to EFI Troubleshooting - https://www.classiczcars.com/files/file/32-efi-book-1980/ As CO suggested, you'd really have to force that connector on to the ECU to get that wire squashed in to place. It's also in the way of pins 8 and 9. Not clear how you accomplished that. And, re CO, the compensator was only present on California models.

I assume that it's sticking open? Probably not going back to the stop, resulting in high idle RPM? Or is it sticking at open throttle? I had to adjust the length of the individual rods on my 280Z to get smooth throttle body operation. It was hard to get started off-idle, causing poor control. You might check yours to see if you can change the leverage angles. Mine was too far over-center. Each end is adjustable. The throttle return springs have to pull all the way back to the pedal. Run it through its range and see how the angles look.

The main reason I wonder about the distributor shaft mounted wheels is because the big manufacturers are still using multitooth wheels directly on the crankshaft, like linked below, and even Nissan went with 360 signal slits in the 90's distributor systems. Computers might not have been as powerful then. When I see the smaller wheels with fewer teeth it just makes me wonder. I'm not criticizing, just talking. There are many different types of systems out there. It can get messy. But it will be satisfying when you're done, I'm sure. https://www.michiganmotorsports.com/ls-performance-parts/58x-crankshaft-reluctor-wheel-12586768-fits-ls3-l76-l98-ly6-ls4-4-8l-5-3l-5-7l-6-0l-58-t/