Captain Obvious

The only time the BCDD does anything to decrease emissions (reduce HC) is when you are coasting and have a high intake manifold vacuum. So unless they measure the HC while they are decelerating driving the car, or blipping the throttle and seeing what the HC's do while the RPM's are coming back down to idle, then the BCDD won't make any difference to your emissions test. Under steady state conditions like idle or 30mph steady cruise, the BCDD doesn't do anything and has absolutely no effect on performance or emissions or anything at all. Under steady state conditions, it's just a closed valve. However... Don't get me wrong. I'm a tree hugger at heart and am glad to hear that you are proceeding with a plan that keeps your BCDD intact. Just clearing up some of the technicalities about the operation. Oh, and Wayne is the man.

Hmmm. Other things to consider... In the later (latest?) years, 78 I think, they stopped putting the altitude correction nubbin at the bottom of the BCDD. Probably except for CA. So I don't know how detailed your visual inspection is, but you might need one from 77 or one from a CA 78 car. The final version still has an adjustment screw underneath, but doesn't have the bellows inside for altitude correction. Seems like the kind of thing that every state except CA would not have let them get rid of. There's one of those stubbier BCDD throttle bodies sans altitude correction for sale right now in this thread: https://www.classiczcars.com/forums/topic/61556-280z-oem-parts-fuel-ignition-door-stuff-grill-etc/ Other thoughts? Again, not knowing how rigorous your CA inspection is, but the energetic Z owner could be able to disable the BCDD internally and prevent any leaks while still having it appear externally as though it's fully functioning. Not that I would encourage such behavior, but if it's a trade off of selling the car out of state or driving it...

Cool tool. It's not a direct measurement of airflow (like the flowmeters are), but it's better than nothing. I assume set them to zero (or at least the same between the two) to match them before starting the engine? There's no guarantee that the distance from the top of the carb dome to the piston inside is the same between carbs. I would also be a little tentative about driving around with those on the car. You won't have any suction piston damping and will lean burst when you press the gas pedal. One backfire (front fire?) and your dial indicators will likely be slammed to the limit and probably damaged.

Pretty much every Z I've messed with is in this category. AFM's adjusted to account for vacuum leaks. Idle speeds adjusted to account for BCDD leaks. Etc...

Well don't get all hopeful yet guys. It's just a theory. The simple (the Obvious) one to look into. Hopefully it's that easy, but it's still a potentially failed avenue. However, in the end of all this, I do hope you completely clean up all the wiring going to the sensors in the throttle body. Clean, shiny, well packaged.

Well to me, that's a tiny bit of "consolation". Consolation that your car isn't absolutely perfect and incredibly cheap. I was starting to get sore from kicking myself.

Glad to help in my own little way!

Try this... Make sure your battery is up to top charge (after all the fruitless cranking) and disconnect the connector to the CSV (which will disable the CSV). Then hold your foot on the pedal "a little bit" (like where your foot would be when you are cruising on a flat level road) and then crank it to see if it will start. Now, don't expect instant operation... I removed my CSV a while ago and I can definitely tell that it takes longer to start without it. Not enough to make me want to put it back on, but definitely longer. Might take me five to ten seconds of cranking to get it to fire if the temp is 40 or lower? Doesn't sound like a lot of cranking when you read it like that, but count "one-one thousand, two-one thousand, etc" for six seconds and picture yourself holding the key while you do that. It's a significant amount of time and longer than what you've been doing in your videos.

Well I don't have any hard numbers for you, but IMHO that cold start valve looks perfect. I took a quick look through the FSM to see if I could find some real numbers and came up empty. There may be some flow measurement numbers in there somewhere for the CSV, but with a quick review, I didn't find any. Only thing I DID find was in the FI manual... On page 16 where they are describing the operation of the CSV, they say "the fuel injected Z-car needs a choke system which supplies very large amounts of fuel only during starting." So the factory expected amount of fuel is "very large". I think you nailed it.

No technical input (at this time), but props for the Predator reference.

And that color scheme... Deep blue with a wide white stripe? Makes me ill. Who would do that to a Z???

Figure out why about what? Why the cold start put out a lot more fuel than the individual cylinder injectors? Because it's designed that way. Seems completely normal to me. I still think the obvious explanation is that you are flooding your engine by trying to start an engine that was working properly when there was a significant bypass around the throttle plate (the AAR). You removed that bypass and didn't add extra air from somewhere else, but you kept the fuel the same. Did you try holding the gas pedal down a little bit while you cranked the engine? That might not be it, but it's so simple to try!

As expected, I don't see an obvious smoking gun, but here's a couple things to think about and/or look into. First, all that TVV thing does is block the vacuum to the EGR system until the engine warms up. It should be a closed valve until the engine warms up and this disables the entire EGR system. You can "manually" disable the entire EFR system by pulling the tube off the underside of the throttle body and capping it. This won't work for you when inspection time rolls around, but just for troubleshooting this current problem, it would be easier if that thing wasn't hanging off the engine. And as a caveat (1a) to the above... The vacuum source for the EGR system comes off a ported source from the throttle body that presents no vacuum at idle anyway, so that whole thing shouldn't be doing anything at all unless your foot is on the pedal. It's similar to the distributor advance vacuum... Nothing at idle, nothing at WOT, but highest at light cruise position. Second, the simplest suggestion would be to try pushing down on the gas pedal a little bit while you try to start the car. Your AAR looks to be open a significant amount and once you took that off the car and blocked the holes, you have removed that amount of idle boost. Your car may simply be completely clamped shut now and can't get enough air to even idle. Try holding the pedal down a little and see if it'll run. Third, I see the rubber stopper in the intake duct for one side of where the AAR used to connect, but I'm not sure what you did with the other side over on the throttle body top. Looks like aluminum foil or something? The point is... The AAR connection side coming off the throttle body is the high vacuum side and needs to be sealed very well. Even more important than the side coming off the intake duct. They're both important, but because of the high vacuum on the intake manifold side, that side needs to be even better. Fourth... All that wiring going to your potentiometer and the water temperature sensors in the thermostat housing? Ewwww.

I saw the pipe, but didn't know what it was. Miles and miles away!!!

@Jeff G 78 Wow... That is many many miles away from what I consider a good time. Woof!

Can you take a decent res pic or two of the engine? Maybe someone will spot something?

Forget the dash... Are those un-rusted original frame rails? Don't drive it like you stole it. You totally stole it. Just don't drive it like that. It'll give it away.

Well since this all started when you messed with the AAR, the logical conclusion is that the AAR work is related somehow. Of course, there's always the possibility of a completely spontaneous unrelated failure, but let's just mess with the idea of the AAR being involved somehow. I don't know what's going on, but I'm just gonna poke around a little. At the beginning of the thread, you said you took the AAR off. What exactly did you do? You detached the electrical connector off the AAR and then what? I assume you loosened a couple hose clamps and took out the bolts that hold the AAR to the intake manifold and pulled the AAR off the manifold. Did you cap the connections that used to go to the AAR (right way)? Or did you put in a piece of tube to connect the two ends where the AAR used to be (not the right way)? Did you take off any other electrical connectors as part of the job? Cold start? Throttle position sensor? At the beginning of the thread, you said you had spark. Are you sure?

The tip of the plunger doesn't really stick out of the end during normal operation? Like this? There's normally something else covering the outlet end of the injector, isn't there?

What's the latest on this? With the sudden onset and complete (not intermittent) failure, it seems like it should be a simple issue to find and fix. "Should be." If I were anywhere near you, I'd be happy to come over and help figure it out.

Back when I had my Z32, I dissected a couple failed 300ZX injectors (different style), but I've never done any autopsy work on a 280Z injector. I'd be happy to do so if you (or someone else) wants to send me a surplus injector or two. I would have to dig out my Z32 injector box to be sure, but I don't think they used stainless steel. I think it's carbon steel, and therefore susceptible to rusting. I assume they believe that situation won't occur as long as the internals of the injectors are constantly bathed in dry fuel not containing any water. Just like the gas tank. But if the car sits for a long time with the system open, water can accumulate where the fuel is/was. Just like the gas tank. The point is... If they didn't make the internals out of a magnetic stainless, then there may be some rust inside inhibiting movement.

Excellent. Make sure the brass connections on the car are really really clean (600 or 800 grit emery cloth) and make sure you get the links in the proper locations. Biggest one on the passenger fender side of the block closest to the radiator:

Pics of the underside or it didn't happen!

I didn't see this before. Yeah, I don't remember all the details, but I went through the same thing with the first door lock I opened up. I know I used a couple little screwdrivers and other pointy tools, but I don't remember how many times I stabbed myself. I do know that I used screwdrivers and little chisels that I ground to shape to try to make the job easier, and while I did succeed, the face caps were a little ragged around the edge. The current set of tools of my pliers combined with the anvil holder have produced results good enough to re-use the face caps.

Sorry. I was off-line for a day. Just sent you PM.