Zed Head

I kooked for something on the first pages of the engine control chapter and didn't fnd 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

Makes sense. I think that they advertise it as an addition or as a standalone. Seems odd that the user would need to choose though. Maybe they knew it was failure-prone, and provided a switch so customers wouldn't get stranded. Or for the people nervous about new technology. p.s. without the AI sources linked the results can't be trusted. What you found seems reasonable but...it's AI. Could be a hallucination or rationalization.

Maybe a local parts store has a loaner. If the FPR is really giving that pressure it seems like you'd be running pretty rich. Which might be why your intake vacuum readings are low. But you should be smelling gas in the exhaust, and getting dark plugs.

The fact that the pressure drops to 34 with vacuum on the FPR shows that the pump and fuel path can go lower. If I was ZCD I'd demand that you try a different gauge before refunding. You can't just go off of a company's reputation. Stuff happens.

No picture. I'd still check with a different gauge. In today's world anything can be of poor quality or counterfeit. Damaged in shipping. Who knows. Everything needs to be checked. Even a cheap parts store gauge might tell you something. If it reads 41 also, that's a sign.

Never heard of WebTV. Interesting. I think we were still watching MTV on cable back then. https://en.wikipedia.org/wiki/MSN_TV