NocturnalEmber

I actually pulled the hose connecting the AFM to the box completely off to open up the airflow, unfortunately it didn't change the problem either. I thought I checked the coolant temp sensor and thermotime switch bullet connectors when I installed the new coolant temp sensor, but I'll double check again to make sure they aren't connected wrong.

I'm fairly certain the throttle is opening. I've manually actuated the linkage by hand more often than I've used the gas pedal, and that muscle feel I get through pushing on the linkage directly feels like its opening (difficult feeling to describe, but if you've ever manually operated a throttle linkage you know the feeling and resistance you get when the throttle plate opens and closes.) The black cover of the AFM actually fell off a few times while the engine was running, and I can see the internals moving as the engine would take in more air. I suppose I'll move onto the ignition timing next. I don't' remember the distributor having uneven gap on the left or right of the securing bolt (it looked even I want to say.) but I'll get into it tomorrow and give it a good look through.

Okay, so I followed the procedures in testing the AFM after I pulled it off the car. I tried cleaning the pins with deoxit and some scrubbing action, and after that was done I reconnected the plug to the afm and had the same issue, no change. The first test on pins 8 & 6 was 205.2 The second test on pins 9 & 8 was 114 Third test I disconnected the battery from the car and ran the positive and negative leads from the battery to the respective terminals the manual specified and probed the other two terminals with my multimeter and got 6.xx volts with the plate fully closed, and as I pushed the plate open, the voltage dropped. I wasn't able to reach in with my fingers and push it all the way but it got down to 2.xx volts as far as I could push it, and it had more left to go.

@Zed Head I probed pins 6 & 8 per the instructions. I know it says "approximately" 180 ohms, so I don't know if my reading was out of spec or not, but my reading was 205.2, and it fluctuated to 205.3. Would you consider that within spec?

I forgot to mention I did check the connection at the AFM physically, and it seems, well, pretty snug on there. Would I still be able to probe the pin on the ECU connector plug with my multimeter and check for something like varying resistance by moving the AFM flapper?

Well, for those of you watching the thread, I apologize for the delay. I got hit with a sinus infection and wasn't operating at my best, so it took me until now to find some motivation to get things done. I took a video that I uploaded below of the car after I installed the fuel pressure gauge inline in between the fuel filter and rail. The fuel pressure I believe is on par with what it should be, but you can finally see/hear the current state of things. The picture of the fuel pressure gauge is after the car had been shut down. EDIT: I'm very sorry for the shaky camera! V_20231022_225059_ES0.mp4

That was one of the first things I've checked to be honest, On the Z its somewhat difficult to get at, but its just a clip thats under it that locks in place with that little bend of metal that wraps around 3/4 sides, right? At this point I'll pull the AFM out and ensure the connector is seated, I swear I felt back there, but I could very well have felt wrong. I'll get out there and verify the connection and report back today. Sure thing @SteveJ Coil - New (NGK) Cap - New (Standard) Rotor - New (Standard) Wires -New (NGK) Plugs - New (NGK Platinums) Very much fouled now. Regarding the ignition it is completely stock to my knowledge, I don't believe there is anything different from the factory distributor.

It does not have a cat (car is a 1978 federal.) I will say that when I had let the car idle for a few minutes, touching the gas pedal could then cause it to immediately die, and THEN it will move onto the whole "cranks, will fire and try to restart, but will not restart, further cranking is an effort in futility." After it has some time to itself, (I haven't determined how much time that is) it will start again, and the process repeats. Giving it gas when it starts up from cold though will result in the whole situation I described in my last post.

@SteveJ, I pulled up info on my fuel pump at the bottom (I've linked it) Does anything about that seem off? Regarding the baseline on the fuel pressure and in 500 RPM increments - The only thing I will be able to measure is fuel pressure at idle, and then whatever the engine speed happens to be after I apply about 15-20% increase in throttle ( want to say the tach shows less than 1,000 with the throttle increase.) The car won't rev more than a few hundred RPMs regardless of how much throttle I give it. I can give it 10% - 100% throttle, and the engine speed will only increase by (and hold at) a small amount until I let off the throttle. There is no visible smoke coming from the exhaust (blue, black, etc.) I've replaced the Cap, rotor, plugs, and wires before I started the car up, so all of those components are new. I verified that everything is snug with the ignition system to be sure. The fuel pump I installed was I believe a Delphi pump from Rock Auto. Here are the specs: https://www.rockauto.com/en/moreinfo.php?pk=1112295&cc=1209260&pt=6256&jsn=837 Does anything seem off about those numbers to you?

Hey Steve, thank you for continuing to provide insight, it's been critical to getting the car to where it is. In regards to your suggestions: 1)I have a fuel pressure gauge and a T on order that should be here by Friday. To re test the fuel pressure. However, the way the car has been behaving, I've never actually driven it on the road, and its never ran for more than 5-7 minutes at a time inside my garage and all of those times the hood has been open. 2) The problem has been consistent I want to say since I have gotten the car to be able to start after I put in the fuel pump and lines (car didn't have a pump when I got it.) It will start (takes a few seconds of cranking if its sat for weeks), runs very rough, but will generally stay running until shut off and then will not restart when hot (will crank all day and try when hot though, and you can hear it fire but not enough to start.) During this time I can give it throttle, and the rpms will raise a small amount, but after about applying 15-20% throttle, the revs stop increasing for the remainder of the accelerators range of motion. So after it hits what it revs to, it will not rev higher regardless of how much more you push the throttle down, though it will hold that increase until you let off. Plugs have maybe 1/2 hour runtime and are black. 3)I will try the percussive maintenance. All of your diagnosis and troubleshooting suggestions have helped tremendously. I now have fully working gauges, the issue of the interior warning lights intermittently working has been solved, and the brake light on the cluster and signal now works (with the exception of the left signal which stays on, but I believe that to be the signal switch itself.) So the car has come a tremendously long way.

@SteveJ Hey! How are ya! I thought you had disappeared! I looked at those online, too, and they look like they are lacking the tab cutout in the center of the bottom of the female piece that sticks up to lock them into the factory plug, Maybe its just a stock ish photo, and the ones with that part number actually do have the locking tabs on them? Based on what's changed in my thread, did you have any suggestions Steve on what you would recommend I look into to get the engine running better and actually able to rev more than 20% without hitting an invisible wall? (and of course the no hot restart). Much appreciated!

Another random sidenote: I replaced the green fusible links today (the ones on the harness near the battery) with ones I got from Zcardepot. Does anyone happen to know of a better supplier for these? They lack the locking tab on the ends of the fusible links and as a result they come loose from the connectors very easily. I'm really worried about these just dislodging from the connectors and breaking the connection when the car becomes roadworthy. So if someone can recommend a place I can buy the oem green fusible links on the wiring harness near the battery that have that locking tab to hold them in the factory plugs, that would be awesome! The car has come a long way since I have gotten it, but this running issue is definitely a tough one.

I took a look at the AFM vane and thought I'd snap a picture in case it tells a story for anyone. Nothing looked out of place (to me), but I've only worked on a total of three cars in my life that have utilized an AFM. The large grey piece and its respective component moves smoothly back and forth when you apply pressure. Just seems kinda weird how theres three copper prongs that just don't move or go to anything, though.

I think I'll break out the FSM and go over it, I know I remember seeing the page for testing the ECU pinouts with a multi meter, I just have to find it again. Edit: Yeah, I did read that the ECU's are the same and the extra pins aren't connected to anything. Much appreciated! I do remember coming across that thread and I think someone suggested they were all compatible, but I was skeptical because the earlier ones I believe distinctly lack pins on the ecu side plugs itself.

Looking into it closer, they are refurbs. I've noticed some distinctly have less pinouts than others; Assuming the ECU ends up being what is at fault, am I limited to a certain model year, or are any 280 Z/ZX ECU's compatible ?

I wouldn't say I smell raw fuel in the sense of it smells like gas coming right out of the pump. The car doesn't seem to smoke at all (especially not black smoke) but the exhaust does smells. This isn't a rotten egg smell like a bad cat, it just smells like..strong exhaust. I just chalked it up to the car being 45 years old with a lack of emissions standards and it running poorly. The tach definitely doesn't jump around, but I want to say a time or two it seems like it got stuck around 500 (when I turned it off it took a bit of tapping to have the needle drop.) I don't remember it doing this recently, though. I'll give it some shaking and rapping on the ECU cover and see if that makes any difference. Edit: On the off chance the ECU is suspect, Would a second hand one be a safe bet? I noticed they can still be had new..which is surprising.

I do indeed have the Fram G3 inline coming out of the tank. Gas looks perfectly fine. I did, and it was correct, but I thought there wouldn't be any harm in re testing. The Airflow meter's cover has fallen off on me numerous times when I got the car to first start, so it wasn't held on there by much, and I think in the for sale pictures when I bought it the cover wasn't on and the vane was exposed. So it could have been tampered with? To summarize: When I got the car I replaced the following with new parts: Fuel Injectors & seals. New aftermarket fuel pump. IGN ignition coil Distributor cap Plug wires Plugs Soft fuel line from tank to pump and from pump to hard line. (5/16") Fuel filter in engine bay Soft line from and post fuel filter inside engine bay. (5/16") All fuel injection clamps have been replaced, no leaks. fuel injection relay (under the dash) has been replaced with new at SteveJ's suggestion. (I measured voltage numbers with key ON/Off at the plug for the fuel resistor under the dash as SteveJ requested, and all of those I believe were within spec, hence the replacement of the relay.) Fusible links on passengers side strut tower have been replaced with new. Ignition Switch has been replaced with new (Beck Arnley.) Oil Pressure Switch has been replaced with new Beck Arnley unit. I also went and replaced ALL of the fuses on the passengers side kick panel. Every single one tested fine with a fuse tester, but on closer inspection, they were almost all oxidized internally and I suspect this was building up resistance and heat because when I replaced them all with fresh, new fuses, problems went away (some of the three pod gauges in dash started working), my BRAKE light in the dash went from being dim to full brightness.) Turn signals started working, etc. I suspect these old fuses were causing extra resistance because of how old/oxidized they were. Fuel pressure has been verified as okay, but I am retesting on the off chance the gauge could have just been inaccurate. So my current state of affairs are, the car will start when cold. Sometimes with no effort at all but a key flick, sometimes after some cranking. When it does start, it will run like it doesn't want to be ran (can only rev by a few hundred RPM regardless of how much throttle is applied, and generally once its been running for a few minutes, if you touch the gas or shut it off, it won't restart again until for a few hours.) On the bright side, all the gauges now seem to work and respond as they should, and the car will start on its own without any kind of starting fluid, but its just..rough when it does. Plugs have maybe (on the extreme guessing side) 30 minutes of runtime on them and are all black. I have no idea if it's misfiring, if the distributor timing is off (though it looks secure), or what. I've checked the grounds, to my knowledge they all look clean and snug.

Another update! I apologize for the long delay, but I can say the thread is now back on its original track. I managed to get the ignition switch replaced with a Beck Arnley one. As for changes, The key positions definitely feel more noticeable moving between them. The car now consistently will click the relays when turned to ON, The BRAKE light in the cluster shines brightly and the seatbelt warning light will also come on and shine brightly and will then will go off after a few seconds. Unfortunately, the main problem hasn't changed. I attempted to start the car. I flicked the key to start, the engine rumbled to life and for a half a second then died. I attempted to start it again, and within a second or less of cranking it started, doing its usual pattern of behavior of "why did you wake me": Running rough, Tachometer reading barely above 500rpm. I attempted to give it gas, and just as before, it would increase the revs by a few hundred (not breaching 1,000 according to the tach) and after about 15-20% throttle, the revs would stop increasing but they would hold at their current state as long as I kept the throttle pressed. If I continued to apply more throttle past this 15-20% mark, the revs would stay the same like I had mentioned, like hitting a small wall. At this point I turned the car off again. I am currently waiting for my fuel gauge to arrive, but as of now, the oil pressure sensor has been replaced as I notated in my last post, and the ignition switch has now been changed out. Does anyone have any ideas of what I should pursue next? I honestly thought about looking at the AFM per the FSM, but all I managed to do was check the ground thats bolted to the AFM bracket, and its clean and snug.

I think i was looking around but I was having a difficult time finding one that would fit inline, I supppose one from a company like glow shift would work with an inline T fitting/barb? Also, finally an update for everyone! @SteveJ, I did install the BeckArnley sensor, and it threaded in like what I would think a tapered thread would (worth mentioning, the Duralast one only made it in a few microturns before resistance, so it MAY not be the proper thread for anyone reading this, as well as the size being way off.) I attempted to start the car, and after a few cranking attempts (to re build fuel pressure is my guess) the car slowly stumbled to life, idle was reading about 500 rpms...and...the oil pressure gauge actually rose from zero! Now I have no idea what the actual reading was, but the gauge is actually reading now with the sensor. However, I am still having that previous issue where when I would give it gas, it would only raise by a few hundred RPMs and then hold there with throttle, even if I pushed the throttle further. Was slow to rev as well. Sounded like trying to rev a car with the distributor timing retarded by a large amount if I had to try and put a sound and behavior to it. When I let off it would return to its stumbling "why did you wake me" state. I turned it off at that point not wanting to push my luck further; I still need to install the ignition switch.

I haven't had the opportunity to order one yet, but I will likely order the T for a standalone oil pressure gauge. As for the fuel pressure after the main filter, probably wouldn't hurt, but judging by how black the plugs were after half an hour of run time max, I think they are getting fuel lol (though I do understand that its a wise choice to have one tee'd in for diags.)

Sorry for the delay all, but I finally was able to get a Beck Arnley oil pressure sensor sent to me. I figured while I had the two (Duralast as well) that I might as well do a little comparison between them. Body wise the Beck Arnley looks to be alittle larger, and there seems to be some sealant over the bottoms of the connector terminals on the Beck Arnley that the Duralast doesn't have. Perhaps the biggest difference is the sheer size of the opening for the oil to flow through. The diameter is huge compared to the Beck Arnley. Would this have an effect? I honestly can't say if it would or wouldn't myself, but I'm going to be putting the Beck Arnley one in and I'll report back with hopefully a smoothly running car so this thread can get back to the electrical side of things! Photos below for comparison for those that are interested:

I've got a bit of a conundrum here I'm hoping someone can help me solve (I apologize enough for this being off topic the past page or so related to my oil pressure sensor stud.) So anyway... The thread size for the oil pressure sensor is 1/8" BPST based on what I've looked up and what Yarb has confirmed for me. I have a replacement Duralast sensor (I was able to get it locally, and its a two prong for my 78) that I mentioned, but something just didn't feel right when I tried to thread it in; The sensor threaded in a few micro turns, then hit resistance. While it is tapered like @Captain Obvious mentioned, that would explain it, but something in me just couldn't shake the fact that something may be "off." (Maybe its paranoia.) So I went online and ordered an adapter that to my understanding (if someone wants to check me feel free) goes from the 1/8" male BSPT, to 1/8" NPT female. My reasoning here, was I wasn't sure if since its a Duralast sensor, if most cars would be NPT and not BSPT, so I wanted to check before I started threading this thing into the block. The verdict? The Duralast sensor will thread into that adapter probably a good 2-4 full turns before it meets resistance, so a lot. If I try and thread the Duralast sensor into the block, it will go a few micro turns like i mentioned before it meets resistance (maybe this is because its tapered.) I guess my end question is, how can I tell if this Duralast sensor is NPT or BSPT? it will thread into an NPT female adapter much further before it meets resistance than when I try threading it into the engine block. Out of an abundance of caution, when i meet resistance I stop to avoid damaging threads. Is it possible this sensor is NPT and not BSPT? Some pics below for thought; I'll also have my report on the ignition switch replacement after I get this situated. Adapter is supposed to be 1/8" male BSPT to 1/8" NPT female Adapter and sensor side by side Gauge screwed into the adapter. The point at which I stopped here is the second I started to feel slight resistance. Threads are fine on both; The sensor threaded in a good few turns fine. If it was BSPT like its supposed to be, wouldn't it have an issue going into an NPT female thread?? I can't tell if the adapter is tapered on either side' One of the comments on amazon did say it threads into a 280z block though. So there's that.

I can't seem to find a thread chaser in 1/8" BSPT...anywhere. I can find a thread tap in that size though. Would it be safe to run a 1/8" BSPT thread tap through the hole in the engine to clean it out? Link below: https://www.amazon.com/RC-HSS-BSPT-Pipe-Taper/dp/B07C73SG99

If you have the part number that would be great!

While I'm at it, does anyone have any experience using the duralast oil pressure sensors? That is the only brand I could find (locally) that is the two prong sensor meant for the 78's. I just want to make sure those have the same thread size before I chase that thread and then try to screw it in.