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What are the facts about 280z ECU compatibility and differences

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    It sounds like your A11-600.... unit has a problem.

    My first WAG would be a blown output transistor and you're running on three cylinders. You should be able to check those big TO-3 buggers in-situ. They're Darlingtons, but you should be able to check them with the ol' Simpson.

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    2 hours ago, Captain Obvious said:

    It sounds like your A11-600.... unit has a problem.

    My first WAG would be a blown output transistor and you're running on three cylinders. You should be able to check those big TO-3 buggers in-situ. They're Darlingtons, but you should be able to check them with the ol' Simpson.

    has a schematic of those ever been found?

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    I've never seen a schematic for the entire ECU. I've reverse engineered a little bit of it (very little).

    One of the sections I DID do however, is the output transistor section. Pretty self explanatory. I'll see if I can dig that up.

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    There's a reference to a Hybridz page in this thread that cygnusx1 supplied a while ago, that shows what some of the components do.  Not in schematic form, but better than nothing.  It's near the bottom of the Hybridz page.  The link still works!

     

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    And about that HybridZ page...

    "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."

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    I really want to get a scope hooked up to the injector so I don't have to fiddle around with the stethoscope and listen for it. Think the process will be to leave the good ecu hooked up, run the scope and video capture that. Then install the bad ecu and scope again to see if there is anything going on up until I manually override the AFM flap. If I had been thinking I would have tried disconnecting the temp sensor just to see if that would have allowed the bad ecu to work (I know that is of little value as far as using it, but would be interesting to see the effect. besides in a road side emergency, it could be something to try, if the defect is overcome by that).

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    You can get the ECU to open the injectors just by triggering three sparks, with the key on.  If the circuit works.  You could probably build a testing device with just power to the ECU, some lights on the injector grounding transistors and a voltage pulse to Pin 1.  People often run their engines with the AFM unplugged.  The base pulse is very basic, apparently it doesn't really need any sensor data.  It's the starting point and all else is an addition to its length.

    Just saying, it's a simple input-output device.  A scope would tell you base pulse length but might be more than needed to see if the ECU works or not.

    image.png

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    The FSM implies that the AFM signal is necessary but it must not need to be generated by the AFM.  Since the engine will run with the AFM unplugged.  The ECU just uses whatever is on those wires at the ECU connector.  Open circuit seems to be enough.

    image.png

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    The three spark test supplies higher voltage to the EFI system than using the starter.  Might be a clue.  Plus it's quieter.  Easier on the brain waves.

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    is that when I just make and break the pin 1 signal from the coil? so I do a make break 3 times and I should hear an injector click. Will give it a try with the working ecu, then again with the non working ecu.

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    Breaking the Pin 1 circuit might work but the standard method is to make and break the coil circuit.  Create a spark at the coil.  Pin 1 needs to be connected to the circuit, of course, like it would be on the engine.

    Somewhere out there I think that there might be an actual Nissan write-up on it.  Can't remember.

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    ok so on my spare engine I will go with ign on, jumper the neg side of the coil to ground (tap tap tap go ground that is), that will simulate what the spark module does and create the pulse in the primary side of the coil (and generate a spark for that matter). I don't think I would need to disconnect the spark module for this. Heck I even have a spare dizzy that I just installed a new reluctor on, could just hook it up and spin it! check my spare dizzy and look for the injectors firing as well.

    The spare dizzy is really nice, good working vacuum advance, zero play in the shaft, nice smooth feel to it. the old reluctor had some chips in it like it got too close to the coil.

    Edited by Dave WM

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    Here's the FSM test procedure for 1978.  It still uses engine cranking, but distributor spinning gives the same effect.  I still think that there is another test procedure out there, maybe in the EFI Guide.

    image.png

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    todays test:

    small ge47 light in stalled in place of an injector (just unplugged the harness from the injector, then plugged in the light to the harness) started the spare engine, starts right up with obvious miss, but light is flashing so I know that works with the good ecu. turn off engine.

    Next hook up spare dizzy in P with the existing one (I have the installed one hard wired to the  module so I left it in circuit. with ign in the run and the fuel purged via the fuel pressure gauge so as not to squirt gas into the engine from residual pressure, I manually spin the spare dizzy by hand, can hear the injectors fire and can see the light flash. That test the spare dizzy. ign off

    install spare bad ecu, ign back on, spin dizzy light flashes. hard to say if it was noticeably not as bright a flash or a duration of flash, but it did and the injectors were clicking as well. So the bad ecu def is functional just seem way to lean. I test this by trying to start it again,m would run for a few seconds (fuel pressure good, light flashes, spark there) then stop. If I depress the AFM flap manually.it will idle, if I throttle up  while manually depressing it can transistion to running on its own but will forward fire (back fire thru the AFM) if I start to back off the throttle. It actually launched my poorly attached AFM, nearly hitting my parked Z.

    Clearly it wants to run lean. I wonder if I need another sensor/s input for this one,. it appears to use all the pins (they are all there and soldered to pads with traces). Maybe an O2 and/or a altitude sensor? I wonder if its seeing a high altitude (I am at sea level) with NO sensor and leaning the mix out?

     

     

     

     

    Edited by Dave WM
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    You might check the PCB circuits in the ECU that are connected to the sensors that control fuel enrichment.  Coolant and air temperature sensors, for example.  The AFM pins.  If I had it sitting in front of me I might just check continuity from the PCB trace to the pin at the connector, for starters.  Broken solder joints at the connector have been found and fixed, in past threads.  If those are solid, then the components at the ends of the traces.  Depends on how far you want to dig in to it.  Could be fun.  Finding that it starts lean. too lean to keep running, is a big clue.

    Edited by Zed Head

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    will be digging in. for starters I am going to see if the 78 FSM has any mention of other sensors as well. I think that is the year that the ECU pins were all connected. I don't know for sure what year this ECU is from. I do know it has large alum guide ears on it if that is a clue.

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    Some of the ECU's have all of the pins but many are not connected to anything.  There's been a discussions about it.  Chalked up to manufacturing "efficiencies" or overstock or things along those lines.  

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    Yea I read that, but visual inspection IIRC had traces to all the pins, all soldered and going somewhere (not just pads). I will be confirming that.

    I just read up on the alt comp, leans it 6%. Also if I read the 1978 FSM correct I should NOT have continuity between 12 and 9 for low alt (sea level). The wiring harness I have does not support a alt comp device so I presume "as is" there is no continuity, therefore should NOT be an issue. That and a 6% even if I am wrong does not seem to be enough to require such a large deflection of the AFM flap. I don't know how the signals are coupled to the circuit, I assume since the sensors are DC, then no capacitor issues, possible a resistor has gone out of spec, but without a schematic its like shooting in the dark. I don't want to go around probing with a multimeter set to resistance and end up frying a IC. Besides that the parts look to be high reliability so will have to stick with just a visual and look for an obvious defect. The fact that it works at all make me think its a base signal issue, the AFM flap effect it, the trigger is working. I suppose I should try it with the engine completely warmed up to see if the cold enrichments could be the problem (air/water/start). Still would not know how to effect a fix if one or more of those was the issue.

    IF its a base signal, IC2 seems responsible for setting that up, Not sure how the freq is derived, been a while since I messed with IC wave generators, IIRC I made some up as a kid from 556 and resistor/cap values.. CO HELP!!!! I don't even know if the IC's have marks on them, they are the round can types not DIP.

    If it had vacuum tubes I would be more comfortable....

    Edited by Dave WM

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    oh and the 78 did NOT have an O2 sensor either. Guess that came on the later ZX. Again since all my pins "seem" to go somewhere I really don't know what I have in the way of an ECU.

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    I am going to try hooking up my AC analog simpson and see if I can get a voltage reading instead of just the lamp. will do with good and bad ECU. I recall disconnecting the temp sensor trying to get it to run, but I forgot to look a the light to see if was flashing brighter (FSM check for correct operation of ECU). If that is inconclusive (the simpson) I will get out the scope. That should give me some clarity on the signal for comparison. I will do this with the spare dizzy so I don't have to spin the engine over for testing.

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    9 hours ago, Dave WM said:

    If it had vacuum tubes I would be more comfortable....

    LOL!

    The IC's have numbers on them, but there's no info (that I can find) anywhere about what's inside. My assumption is that they are parts made by Hitachi for use only inside Hitachi produced devices and they didn't publish datasheets for them outside their own business.

    So you put a lamp in place of one injector and it blinked. That tests one output transistor. Can you move the lamp around to the other injectors and make sure the second output transistor is "working" too?  If the wiring harness hasn't been messed with, I believe the injectors are grouped 1-2-3 and 4-5-6. You can pull the ECU off the harness and Ohm out the wires to the main ECU connector if you have to.

    As for the altitude compensations and stuff like that... The cars that did not need that stuff (non CA?) simply did not have them installed. My assumption is that the ECU defaults to "normal" non-altitude corrected if the other stuff is just left as no-connects. In other words, I strongly assume that you can just leave all the altitude compensation pins unconnected and it should work like a 49 state version.

     

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    The engine will run on three cylinders.  Somebody actually cut one in half and ran it that way, if you recall way back.

    The Kent Moore Analyzer manual has more info that might help understanding.  There might be a pdf file on the site but in the meantime there's this web site, broken down by single pages.  - http://datsunforum.com/efi-troubleshooting-kent-moore-j25400-analyzer/

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    I can check the other bank, but I am pretty sure they are working, I can get it to idle fine (no missing) IF I manually deflect the AFM vane about 20 degrees. Once I open the throttle up, it runs normally (no manual deflection of the AFM required), so the problem seems to be isolated to low throttle or idle. I know the TPS is working since the other ECU works fine in the test stand. I maybe wrong on "runs normally at high throttle though, I did not run it very long that way, and as soon as I let off the throttle it backfired and blew the AFM completely off the throttle body.

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    47 minutes ago, Dave WM said:

     as soon as I let off the throttle it backfired and blew the AFM completely off the throttle body.

    Now that would have been a good video.

    • Haha 1

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