Captain Obvious

Wow. That sucks that you had to pull the head just to get the pencil stub out. I've not done that, but I did drop a small bolt down the plug hole in one of my cars once. First attempt at retrieval was a magnet, but that wouldn't grab it because it kept getting stuck to everything else in there. Second attempt was with a shop vac and a small diameter piece of tubing stuck down the hole. Taped the small tubing to the end of the large shop vac hose and went blind fishing. Worked like a charm. That would have worked on your pencil too if you could have gotten ahold of one of the ends instead of the middle somewhere.

There's something I've been meaning to bring up with regards to your A/C install and I kept forgetting. Seeing this post again reminded me. You're looking for a Fast Idle Compensation Device (FICD) to boost your idle while running the A/C. That's the correct part to use. BUT... I don't see any reason why you couldn't repurpose the throttle opener servo instead to do pretty much the same thing. Instead of connecting the actuator hose to the vacuum control valve, you could run a tube over to the A/C vacuum switching solenoid instead. So here I've been trying to show you what the is FICD this whole time, but the more I think about it, the more I think it might actually be easier to find a throttle opener servo diaphragm instead. It's not the RIGHT part, but I think it would work and it's probably much more plentiful. I think every Z from 70 through 74 had one. Even the ones that didn't come with A/C.

Good luck. Sounds like Murphy is luring you into his trap..... You absolutely know that this problem is going to come back again at some time in the future, don't you? At the most inconvenient and inopportune time, right? When that happens, take some more measurements and come back here for some help if necessary. In the meantime, work on the next hottest fire!

I'm not so sure. I wouldn't think it would go intermittent. I would expect once and done. That link runs a bunch of other stuff as well including all the dash gauges. There would be other effects. On second thought... Wait a minute... You said the tach dies also?

No, no... It's great info. I was just adding some additional info to make things, ummm... "easier"? That FI combo relay system is a pain in the butt. I think it's a lot more complicated than it really needs to be, but I wasn't there when they designed it. The diode is between pins 36 and 76. Pin 36 is the fuel pump control from the AFM and pin 76 is the fuel pump control from the START signal. The diode OR's those two signals together so that either of them can power the fuel pump. In normal use, the signal from 76 is used first while cranking, and then once the engine spins up to speed and you stop cranking, the signal from 76 goes away, but by then the signal from 36 takes over instead.

Zed Head, About the info you posted above... Yes, you are right that there are actually FIVE fusible links on the EFI cars with the fifth one coming directly off the positive terminal of the battery. That's the one you identified as #4 in the sketch. But... That fifth link (item number four) runs the injectors and a bunch of other stuff related to the FI system, but it doesn't power the fuel pump directly. It DOES supply power to the AFM switch, so it does provide the primary side control power for the AFM signal once the car has stopped cranking, but other than that it has nothing to do with the fuel pump. The fusible link that directly runs the fuel pump and the AAR is the driver's side rear link located in the fusible link blocks. Also note that the link that runs the fuel pump and the AAR is the one in the schematic you posted. Also interesting to note that the other FI link (item number four) that comes right off the battery is not shown at all on that schematic. Haha! Don't mine me... I'm just trying to make things more complicated by making them simpler! On edit - I fixed an overextended statement I made prior.

I posted this in another thread where there seems to be fuel pump issues, but it's probably applicable here as well. So are you familiar with the numbers on the FI combo relay? Here's the pin numbers related to the fuel pump and AAR: - Pin 73 is power from the battery. Should be hot at all times.- Pin 76 is the control signal from the ignition switch. Should go hot only in the START position.- Pin 36 is the control signal from the AFM. Should be hot only when the AFM is passing air.- Pin 74 is power output to the fuel pump. Should be hot in START and when the AFM is passing air. The system works like this... Power comes from the battery through the driver's side rear fusible link to pin 73. When either control signal (pin 76 or pin 36) goes hot, the relay connects pin 73 to pin 74 which then goes to the fuel pump. So when either in START or when the AFM is passing air, pins 73 and 74 are connected together and that sends power to the fuel pump. So in your case, one or more of those four pins isn't working properly. Either because of a wiring or connection problem or a problem inside the relay itself.

The fuel pump control side of the FI relay does have a fusible link between it and the battery. It's the driver's side rear link of the four on the wheel well. If you've got 12V on both sides of that link while the problem is occurring, that's not the problem. So are you familiar with the numbers on the FI combo relay? Here's the pin numbers related to the fuel pump and AAR: - Pin 73 is power from the battery. Should be hot at all times.- Pin 76 is the control signal from the ignition switch. Should go hot only in the START position.- Pin 36 is the control signal from the AFM. Should be hot only when the AFM is passing air.- Pin 74 is power output to the fuel pump. Should be hot in START and when the AFM is passing air. The system works like this... Power comes from the battery through the driver's side rear fusible link to pin 73. When either control signal (pin 76 or pin 36) goes hot, the relay connects pin 73 to pin 74 which then goes to the fuel pump. So when either in START or when the AFM is passing air, pins 73 and 74 are connected together and that sends power to the fuel pump. So in your case, one or more of those four pins isn't working properly. Either because of a wiring or connection problem or a problem inside the relay itself.

Haha! CHIPS! I was thinking that the portion of the ECU case where the connector mates is an aluminum casting. I bet if you dropped it wrong, you could chip it.

I posted this in another thread where there seems to be fuel pump issues, but it's applicable here as well. The AAR (you know what/where the AAR is?) is wired in parallel with the fuel pump. You can pop the connector off the AAR and probe the connections inside to see the same signal that the fuel pump should be seeing. Put a little noid light across those two terminals if you get energetic. Something you can see easy from the driver's seat. So just like the fuel pump, the AAR should have 12 volts across it's two terminal connections: - any time the key is in the START position, and/or - any time the key is in the ON position and there is air flowing through the AFM. So, if you've got power to the AAR at the correct times, you're looking for a bad fuel pump or connection to it. But if you're not getting the correct signals at the AAR either, then you've most likely got a problem with your FI relay. Would be interesting to see what happens when your car shuts off from lack of fuel. If the AAR still has power but the fuel pump has stopped is a different issue than both the AAR and fuel pump losing power at the same time.

In case you want one other thing to check before you climb back under the car to take a closer look at the fuel pump... The AAR (you know what/where the AAR is?) is wired in parallel with the fuel pump. You can pop the connector off the AAR and probe the connections inside to see the same signal that the fuel pump should be seeing. Put a little noid light across those two terminals if you get energetic. Something you can see easy from the driver's seat. So just like the fuel pump, the AAR should have 12 volts across it's two terminal connections: - any time the key is in the START position, and/or - any time the key is in the ON position and there is air flowing through the AFM. So, if you've got power to the AAR at the correct times, you're looking for a bad fuel pump or connection to it. But if you're not getting the correct signals at the AAR either, then you've most likely got a problem with your FI relay. Just thinking it's easier to check for that signal standing up at the front of the car instead of laying on your back under the rear of the car. And, unfortunately, rossiz is correct that his trick with the oil pressure signal won't work for your year. That only works on 78's.

Good. You have to start from ground zero. Just remember that the ECU has absolutely nothing to do with whether the pump will run or not. The fuel pump should run: - any time the key is in the START position, and/or - any time the key is in the ON position and there is air flowing through the AFM. So step one... Pull the small black/yellow starter solenoid wire off the starter, turn the key to START and listen for the pump. If it doesn't run, check for power back at the pump and if you have power there, you need to check the pump integrity. If you don't have power there, then you need to start backing up to find out why.

I don't know how much of the design of the boards was done by Bosch or by JECS. I haven't researched the origins of the two parties involved, other than a quick snippet from Wikipedia: "JECS was formed in June 1973.[1] It was a joint venture between Robert Bosch GmbH, Nissan Motor Co. and Diesel Kiki Co., Ltd.. It enabled Nissan to use Bosch's engine control technology, and gave Bosch access to the Japanese market." I suspect the concept, original schematic, proof of concept demo board (probably with NO IC's at all), and of course patents were developed by Bosch, but the implementation (and integration of some of the electronics) was done by JECS. As for the portability of the resistor designations in the info you found back to our ECU's? Unfortunately I doubt there is any portability at all. I agree that it would be neat to have the experiments duplicated with our generation of ECU, but I've not seen that done. The closest I've ever seen is what you dug up. I've poked around a little and have done some reverse engineering, but just enough to be dangerous. I also agree that time spent on reverse engineering the old one might be better spent working on something newer.

cygnusx1, Not sure what you're asking about the knockoff version... L-Jet was used on lots of other cars other than the 280Z and some of those other cars continued to use improved versions of the L-Jet for a number of years after the first gen Z ended. I'm not saying that anyone is using knockoff versions. What I AM saying is that I've been through those docs you found and after study, it's clear to me that the ECU under analysis by the author is NOT from a 280Z. Why do I say that? - Because the pics of the boards are significantly different than the ones in our Z's and is clearly much newer production. I know that because there are several DIP IC's used and the board is CAD routed instead of the old hand routed boards that we use. - The component designations used in that old info do not exist on the boards used in our Z's. We do not even HAVE an R616 or R758 for example. - There are a few references to the use of a lamda sensor. They started including a lamda sensor input in the later years of the L-Jet, but that wasn't until the 280Z was out of production. So what I'm saying that I think the info you found applies to a newer version of the L-Jet that was used after the 280Z production ended. There are a few references to Alfa Romeo in the docs so if I had to guess I'd assume that's what he was working with.

cygnusx1, Thanks for that and that's some awesome info, but I don't think it pertains to the first gen Z's. I've been through that stuff from all angles and I believe the work done on those old internets pages is from a different ECU. Might be a ZX, but it's not a first gen. Haha!! Too bad Al Gore isn't a forum member. I bet he could help with tracking down the origins!

Thanks much for the pics of that ECU with the DIP packages. Unfortunately no new info. Those are the exact same part numbers that are on the original round heat sinked versions. Still custom, still no datasheets in the public domain, and still made from unobtainium. So have you tried that newer ECU in the car yet? Just to make sure it works?

I took a look for a tach other than the one in my dash and came up dry so I can't add any additional details there. Like you said... One of those puzzles. So yeah, if you get the opportunity and feel like experimenting it would be interesting to see what happens when you pull the tach resistor. My car is still laid up for the off season or I'd try it. C'mon Spring! Maybe your car WAS running the last time you tried it, but since the tach read zero maybe you just didn't know it? What kind of exhaust you got? ::

I took a look at the wiring diagrams and I can't provide any input as to if/why the fuel injection would work properly or not if there was something wrong with the tach or it's series plug-in resistor. I can tell you, however, that it looks like the ignition and fuel injection sections should work just fine even if you were to pull that resistor out of the circuit or if the tach were completely removed from the dash. Not saying it really works that way, but looking at the diagrams, that's how it SHOULD work. I also can tell you that the diagrams don't do an accurate job of showing what's inside the tach. I know there are artists liberties taken at that level of detail, but if the internals of the tach were constructed as shown, it simply wouldn't work. Doesn't matter for this discussion though. So I don't remember if I have a tach laying loose or not, but if I do, I'll take a look inside and see if I can add anything to the discussion. I've never been inside a tach before. They've always just worked for me. Also, Zed Head, you mentioned that the wiring diagram shows a dedicated ground wire through C1 for the tach. I know it looks that way on the page you referenced, but that's just Datsun's way of simplifying the sub-system being highlighted. The tach has no dedicated ground as that same ground goes lots of places. Datsun's thought is that when you are interested in the sub-system (tach in this instance) that you don't care about or need to know about where else those wires connect to. So they "simplify" the sub-system diagram accordingly and don't show all the other places the connections go. If you want to see where else a wire goes, you have to refer to the complete wiring diagram. I've found that scheme a help or a hindrance. Helps when you're trying to figure out how a sub-system works, but it's a hindrance when you're trying to figure out "so where else does this wire go".

Glad the shafts fit well. As for setting them up on the car, I think there are some great guides already posted in the carb sections of the site, but my words of advice would be to make sure: - The carbs are spotlessly clean. - The throttle plates are properly installed in the shafts and centered in the carb throat bores. In order to get them perfectly centered, you'll have to loosen up the stop screw on the linkage so the butterfly plates actually contact the carb throat. Remember to reset the screw after you've got the butterflies perfectly centered.. - The needle is properly centered in the nozzle and that the needle or nozzle isn't worn from contacting each other due to prior maladjustment. - The float bowl level is correct. - The nozzle enrichment function (choke) slides easily without any binding. - The oil level in the damper is at the correct level. - Set your nozzles two and a half turns down to start and make triple sure you don't have any vacuum leaks. Anywhere. At idle, the engine isn't sucking a lot of air and you need every last molecule going through the carb venturis, not around them. If all of the above works out as intended, the engine should run and then for the fine tuning, you can use one of the guides in the carb section. I think Blue has consolidated some good info.

Naa. It's not materials used or degradation. It's more the fact that these things were built as IC technology was in it's infancy and some of the standards that are ubiquitous today were not yet in effect yet. Things like "mmyy" date codes that are printed on almost all IC cases don't exist when you don't have IC's in cases. Prior to that standardization, there were other more cryptic methods employed. Usually three characters with coded info that is undistinguishable without the decoder ring that goes with it. Adding to the issue is that every manufacturer used their own Rosetta Stone for translation. For example, NEC's date code encoding wasn't the same as Hitachi's. So while I did find some three character markings on the transistors that are probably date codes, I don't have anyone's Rosetta Stone to do the translation into a date. The best chance for an easy to distinguish date code comes off markings from wheee's newer ECU with the DIP's. Oh, and we've gone full circle on the component markings as well... With the advent of tiny surface mount stuff, many manufacturers don't have room for full info on the parts anymore and have gone back to cryptic markings. More cryptic than ever before. In fact many times there isn't even room for a part number, let alone a date code. Full circle and beyond.

Shaft looks great, but you won't really know until you try it in a carb body. I use a little silicone grease on mine. It's supposed to be an interference fit of course. That's how the O-ring seals. Just a little interference, but there has to be some. Also, I can't tell from the pics, but make sure the groove corners are deburred. You don't want them chamfered, but make sure there aren't any brass burrs kicked up from the grooving operation. Some 600 grit sandpaper should take care of it. You just don't want any burrs that could damage the O-rings during installation.

Great. When you get a chance. On a related note... I popped the case on my spare ECU and went hunting for date codes on components and found nothing easily distinguishable. So remember when I said it would be likely that you could be able to closely estimate the dates of production by determining the manufacturing date of some of the parts used on the boards? Apparently not! I was planning to find a couple easy spots to guide you towards so you could do the same... That's not gonna happen.

Yes, there's no mystery there. It's not a version thing, it's a chronology thing. I've got one sitting in my driveway. An 83 ZX. The 83ZX has a later revision of the Bosch L-Jetronic that includes a Lamda sensor. The point wasn't that it was hard to find... the point is that the ECU they were tweaking in that HybridZ thread by changing the resistor values doesn't apply to us with the first gen Z's. wheeeeeeeeeeeee, Haha! I don't think yours is the holy grail of ECU's. It wouldn't have the same P/N on the outside if it were. I just think it's a newer produced version for the older cars. I'm thinking that in 1990 the factory still had to supply ECU's for people who needed them and there had been so many technological changes in electronics between 1975 and 1990 that the newer ECU's changed some with the times. Form, fit, and function identical to the old ones, but different inside. I'm just wondering if Hitachi decided to get away from the completely custom IC's used in previous versions for more readily available silicon. Or maybe they thought they could sell some of the components on the open market to other manufacturers and started offering them for sale outside Hitachi. I really doubt it, but it doesn't hurt to check into it.

Great, I'd love to have some better pics and some numbers from that newer ECU. No hurry... At your leisure. As for the Hellfire... I believe the only thing holding it up is available time. Lenny keeps fading in and out of consciousness. Maybe if I were to resurrect my somewhat similar project I was working on before he came along and seemingly made my project obsolete before it was ever completed. Maybe I should have never pulled the plug? Maybe if I just TOLD him I was going to resurrect it... ::

I've been through that EFI thread on HybridZ and I wouldn't put any credibility into the validity of the information as it pertains to the guts inside the Z's ECU. The discussion of things OUTSIDE the ECU case are valid, but all the stuff about changing resistor values and such inside the case are suspect. I've been through that info a couple times now and I believe he's working with a different ECU. Bosch L-Jetronic yes, but of a newer generation than what we're discussing here. Might even be a ZX, but I can tell you that it's not a first generation Z. If I remember correctly... The pics are wrong. The resistor designations are non-existent. And there's talk of a lamda sensor. All that spells different ECU. In other words, the overall system info by BRAPP is good stuff, but the resistor tweaking stuff inside the ECU case dug up by cygnusx1 doesn't apply to us. Unfortunately cygnusx1 didn't write it either, but dug it up somewhere else from what appears to be early internet days so it's very difficult to trace.