Zed Head

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/

Just thinking it through in text. Good luck. I think that the crankshaft-mounted trigger wheels were developed and used for accuracy and precision, for fuel economy and emissions. Many of the things we deal with are for that purpose. O2 sensors, catalytic converters, etc. For a performance only vehicle you don't need them.

Sorry to clutter your thread. Since the stock 280Z system uses the same shaft and gears but only six lobes for ignition timing I'm sure it will be much better. As was noted in the Hybridz thread, precision of injection timing is mostly, maybe only, for low RPM emissions.

Actually, maybe it can. If the missing tooth shows compression stroke on number 1. I've wondered about it before. But it's still a camshaft position sensor. I wonder how accurate the timing is. Nissan combined the two sensors in the later ECCS systems. Here's 1993. With only a small number of teeth in the OneSix system, accuracy and precision of the pulses will be low. On top of any shaft/gear play. The concept seems solid but putting it in to practice is difficult. That's why so many of today's cars have a multitooth wheel on the actual crankshaft. Anyway, good luck.

The software can't know without a real crank sensor. It's a pretty common discussion item. https://diyautotune.com/blogs/tech-corner/crank-and-cam-sensors https://forums.hybridz.org/topic/126922-sequential-injection-with-only-crank-position-sensor/#comments

Looks like fun. Surprised that a company that's been around as long as OneSix would mislabel their cam position sensor though. Kind of weird. They should know better. They might be using the "close enough" definition. https://protunerz.com/collections/sensors/products/onesix-industries-l-series-crank-sensor-hall-billet-new https://www.onesixindustries.com/category/crank-angle-sensors Here's a real one. https://hokeperformance.squarespace.com/l-series-crank-angle-sensor

Looks like it might be a John Coffey car. I clicked through an AI overview and ended up on ZCar.com , see below. He used to be pretty active on the forums. He was part of Beta Motorsports, no longer in existence, I think. Unfortunately he died in a motorcycle accident several years ago. https://www.zcar.com/threads/found-another-interesting-z-for-sale.273766/?nested_view=1&utm_source=google&utm_medium=organic#post-1848748

I looked for something on the first pages of the engine control chapter and didn't find anything in that location. But I did find something when I dug in to the chapter. Location seems right in that description. Page EF&EC 63 of 1983 FSM. Shown here but location is wrong -

You could pull a vacuum on the FPR port and see what happens. If pressure drops it's not the pump overpowering the FPR. The FPR is just a valve with a spring behind it. The diaphragm works against the spring when there's vacuum. The typical pressure gauge can be damaged by exceeding its max pressure. There's a tube inside that gets deformed. Does the gauge sit at zero when there's no pressure on it? It's probably a Bourdon type. https://www.streatcontrol.com/a-closer-look-at-the-four-main-types-of-pressure-gauges/ https://www.bourdon-instruments.com/us/en/product-overview/pressure-gauges/c/36822 https://blog.wika.com/us/knowhow/8-common-reasons-for-pressure-gauge-failure/

Don't the two flanges contact and compress the inner races (edit - against the spacer) when the nut is tightened? Essentially creating a shaft with two ball races and preloading to a certain extent the balls against the inner portions of the outer races (the word inner serves two purposes here, axial and longitudinal). Depending on where the measurements are within the range. The distance piece/spacer could be shorter or longer than the housing, according to the table. It's a poorly written spec. Basically says that they're "about the same". Edit 2 - it's been noticed in the past that the procedure for seating the outer races requires the balls to press against the races. Risking Brinelling. Which is generally considered a no-no when installing ball and race bearings. Overall, kind of a crude bearing system.

You can measure to verify. L1 and L2 are in the table, but they didn't call them that. Might be that somebody ran it with a tight bearing in the past. https://www.classiczcars.com/files/category/13-280z/

Can you measure the stroke at the clutch fork? If you're getting full stroke then the problem is probably not with the control system. Could be mechanical at the pressure plate, or something binding the input shaft or clutch disc to the flywheel. Tight pilot bushing is a possibility.

New bearings? The FSM says yes to "??". They're called "distance pieces" after translation.

That's not spec. There's no rabbit hole here. I'm sure it will work just fine. I'm just going by the words people write.

Funny (maybe) aside - I came across a site apparently in the United Arab Emirates. "Desertcart". https://www.desertcart.ae/products/253969950-ngk-u1099-48776-canister-oil-filled-coil

He just wants to use the factory specification from the FSM. The other thread ended without verification of primary circuit resistance for the NGK coil. There's no information out there, ironically. But, a quick check with a meter should answer the question since you have one in hand. Trust but verify. Another option would be to use a ballast resistor in circuit with the Jacobs coil. ~ 0.4 ohms. There's one for a few Mercedes models that appears to be about right. Probably don't want OEM though. Yikes. https://www.authenticclassics.com/Beru-0-4-Ohm-Blue-Ballast-Resistor-for-Mercedes-p/auth-006506.htm

kcpope had a similar problem. About 4/5th's down this page - https://www.classiczcars.com/forums/topic/69986-picked-up-a-78-280z-today-pros-cons-with-some-pics/page/7/#comment-686577