Captain Obvious

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.

Hi Tamo, Great start. I got a couple comments: 1) The black/yellow wire to the starter connects to the solenoid pin on the starter, not the same place as the B+ connection. 2) You've got wire coloring mistakes on the 77 ignition relay. Also, this simplified diagram makes it clear how there's always some sort of current limiting device between the alternator and the battery. That's the point I was talking about in your other thread where you were talking about fuse and wire size upgrades. I didn't spend a lot of time on the 75 diagram. I've got a 77 so I'm much more familiar with that one. Hopefully someone with lots of 75 experience can chime in on that year?

Glad to help. Forgot to ask before, but to double check... What you were originally saying is that you've got three ECU's in your possession and all three of them outwardly appear to be identical. Same part number on the outside of the case and all three "should" work fine in your 76. But you took the case off and found significant differences inside (at least between two of them). And you're wondering "What the heck? I thought all three of these were supposed to be the same?" Did I get that right? I'm intrigued by the ECU you have there that has DIP (Dual Inline Package) components instead of the round ones with the finned heat sinks. The parts I'm talking about have sixteen pins each and have a big "1", "2", "3" on them. Can you take a closeup pic of one or more of those for me? I believe they are semi-custom (not available off the shelf) Hitachi parts, but it would be nice to have the numbers off the tops. If you get a chance?

The (C12-001 004 N) ECU with the larger rectangular multi-legged components is newer than the other one you have pictured. I wonder if it's aftermarket or a newer factory replacement. If it were me, I'd use the newest one you got that runs properly. The pics aren't clear enough for me to pick up any date codes, but it's 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. Also, it's academic, but... The components loaded into that white holder are not resistors They're actually inductors. They use a L-C (inductor and capacitor) as a filter to try to prevent high frequency interference from entering the ECU circuitry. Each pair of little L's and C's is a filter on a pin that enters the case. I bet they decided that some of them were no longer necessary as time went on. Better filtering elsewhere in the car maybe? I wouldn't call the more heavily loaded filter section "overkill". Noise is a tough and difficult to pin down opponent. And sometimes when the schedule is looming there comes a time where sprinkling some insurance in the form of some cheap components is the right course of action.

Rolf, Don't apologize for the description. I don't consider it bad and I doubt anyone else did either. In any event, glad your shop fixed you up!

I can't claim independent invention for any of those stupid kid tricks. I partook in lots of them, but didn't invent any of them. I picked most of them up from the kids in the neighborhood or from school. I have no idea where those other kids got them from. But the propagation of these tricks is astounding. I never knew they traveled so well.

I bet the stickiness with the replacement injector was a result of two things: 1) The fact that it had sat for so long without actuation, and 2) The lower current supplying capability of the 9V battery that you were using to test it. I bet that if you would have connected it directly to your big honkin lead-acid car battery it would have opened right away first time. My brain fart moments now usually result in "$^!#. My back just went. I'll see you in a couple days. I gotta go lay down."

Excellent. This kind of info is invaluable when you need it. You don't need it often, but when you do, it's great to have it filed away. Thanks again for sharing!

We used to mix up that gasoline/Styrofoam stuff as well! Add it to the list of stupid kid tricks! If there's a list, I know I'm certainly on it. This kind of stuff would make a very interesting social study, How (back before the internet) did all of these tricks travel? Could only have been word of mouth, because nobody was writing this stuff down! I'm thrilled that there are other people who have experienced this kind of stuff. And lived.

Excellent. Glad you were able to confirm the leak. It's always nice to find the smoking gun.

Forgive me guys if I'm incorrect, but I think there might be some confusion about what is being asked for here... Rolf, You're looking for a dimensioned mechanical drawing (a "blueprint") for the radiator, right? If that's the case, I don't have what you're looking for, but it might help others understand what it is you are asking about.

Chas, That's a great method for checking the flow balance.