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Thread: Help identifying ECU/Mods?

  1. #1
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    Help identifying ECU/Mods?

    Hi everyone,

    I have a project at the moment with a GM EFI unit that had some physical modification done to it. Can anyone help point me in the right direction of what this might be traced to? It's mid 80s, and had some physical wiring done to the ECU... I'm not getting ignition spark at the moment, and I hadn't had a chance to try to tackle this 'Clone the ECU so you have a backup' project before getting into this predicament. Car was running fine for about a year, went into storage for a year, and now it's making me pay for it! :)
    EFI1.jpg

    Thanks!
    Pete

  2. #2
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    My guess is that someone has changed the injector sense resistors for peak and hold injectors with a different impedance than stock. Does the engine have multiple TBI units or a 4bbl TBI?

  3. #3
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    Quote Originally Posted by 1project2many View Post
    My guess is that someone has changed the injector sense resistors for peak and hold injectors with a different impedance than stock. Does the engine have multiple TBI units or a 4bbl TBI?

    No, it's a 4 cylinder turbo with injection...no multiple TBIs or 4 barrel (if I'm answering that correctly)...nothing too fancy. Is there any schematics or anything that's been reversed engineered on the design of these boards? I may be looking at trying to duplicate the chip, but I'd really love to know why there was all of that manual rework as it would perhaps have to be duplicated....

    Pete

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    Hi Pete,

    It's been years since I've looked in an ecm case and I think I'm forgetting items. I realized that is not an injector resistor change.

    What part number is that ecm, and what are the modifications to the vehicle or engine? Is the small board in the picture normally plugged into the memcal socket?

    Edit: I've found your post mentioning that it's a Lotus. So that's probably a 1228707. There are schematics floating around for much of that ecm: https://web.archive.org/web/20070208...schematic.html

    The 8708 is similar to the 8707 which I believe you have. The add-on board is likely a custom built memcal with an eeprom or flash chip for a custom tune. It will have a resistor network for when the memcal has a problem. It should also have a knock sensor filter. The small chip with the wires may be clock? If you give the part number I can try to figure out what it does.

  5. #5
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    I'll try to get some better pictures together...the outside of the case doesn't have any real numbers, just prototype numbers - Basically it's the setup from the mid 80s that GM used to retrofit the fuel injection to...so even though the 'stuff' is earlier, it became prod (and thus far seems compatible with everything i've run across for a 1989 non-SE version Lotus Esprit which uses the 1228707...or at least something similar with it, that they modified to get working with all this stuff. :) I wanted to understand the mods a bit better and perhaps match it up with what I have, before throwing replacements at it and hoping for the best, especially moving that memcal to something that's not modified and knocking everything out :)

    The 1228708 actually has four separate yellow connectors on it and was used on 1989 SE version Lotus Esprits...different setup overall and not the same connectors I have

    I'll see what I can pull together for better pics/detail

    Pete

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    The 8708 was an underhood, water resistant version of the 8707. Inside the two cases you could find the same chips doing the same jobs. In the US we had a similar case with the 1227727 ecm in Corvettes, which are under the hood, and the 1227730 ecm in Camaros, which is mounted inside the vehicle. The 727 had four connectors and the 730 had three. Another consideration is that the 8708 and 8707 were also both used here in the US. The 8708 was mounted under the hood of "W" cars and the 8707 was used with "N" body cars. These ecms were installed when the car was equipped with the Lotus designed 2.3l Quad 4 engine, and both used the same program to control the engine.

    http://www.gearhead-efi.com/Fuel-Inj...ation-6B-8B-A8

    What you have is definitely from the same family of computers, called the P4. I have a 1227749 apart at home and I would be happy to send pictures later of the circuits. Minus the resistors, you will see much similarity. The 8707 and the 7749 were both used with Quad 4 engines. When the 8707 was used there was an additional input from the ignition module. Investigating both ecm's it is noteworthy that at least one additional piece of hardware is present in the 8707 which is not in the 8709. That piece is a small chip in the area of the board where the chip is in your ecm which has wires attached to the legs. I have never finished investigating the differences nor am I aware of anyone else who has. But I would love to know more about them.

    I have been involved in helping a few people who have acquired unique or one-off vehicles that were built by GM. I have been surprised at how easy it is at times to recognize parts used on the vehicles. Then I have been surprised at how much the owners want to believe what they have is unique in every detail. But the fact is that GM folks are just as likely to use what's "laying around" as a backyard builder. The difference of course is that the backyard guy has a much smaller pile to pick from. ;)

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    Here is a link to good information about the 7727. There are many similarities between the 7727 and the 7808. Again, I realize that it is in a different case and form than the 8707 but the 7727 is very close to the the same ecm functionally. You should see many of the same chips as what is called out in the ECM Map.
    https://www.w-body.com/oldsite/insid...f/ecm-pcm.html

    Here is a link to a page with photos of an in-the-car P4. This ecm could be one of several but I believe it is the 7730. The 7749 and 8707 have additional hardware installed. Specifically, the chip with the resistor and diode glued to the top in your ecm is not present in the 7730.
    https://www.dynamicefi.com/EBL_P4_Install.php

  8. #8
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    Thank you for all the detail - I'll start digging in and checking out some of these areas out! I'm really more concerned with finding something that can replace what I'm looking at in front of me, and keep the car running... I took a few more pictures if it's any help. I backed up what was on the chip with an eprom reader but wasn't sure what this other chip was, or if I can somehow pull this info into a standard memcal (copy it so I don't have this one custom made memcal thing.... On the main module, some of the chips are marked prototype...so that's a bit concerning too...but I do have another module, part 16198267. Would it be safe to swap the memcal into it, or I need to account for all this custom stuff? Just getting into the whole efi scene.

    Pete
    Attached Images Attached Images

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    I am thinking the parts in the first picture are a handmade version of a memcal. You might be able to use information on this page to help figure out how that circuit is wired. If you do, I'd love to hear more.

    There are more pieces here: http://www.gearhead-efi.com/Fuel-Inj...your-Memcal-ID
    Some of the links in the above thread are broken now. The exatorq link brought you to the schematics I posted earlier. Diy-efi.org is an old mailing list. You can follow the thread mentioned here. Also note the picture of the prototype ZR1 Corvette memcal. The ZR1 used an engine designed by Lotus and what we can see of the memcal in the photo looks very much like what you have.

    I have found a better archive of Ludis site (where the schematics I linked originated).
    https://pcmhacking.net/ludis/1227749schematic.html
    This archive contains the schematics for ecm's similar to the 8707. It's been years since I've dug into this so I would have to look at notes on another pc to be of more help.

    At least you have more information, although it may be more distraction than help. The question is "What can replace this controller I am using." My hunch is that a later stock 8707 will be the correct replacement. The reason for all the additional work is to try and help devise tests to prove or disprove the 8707 will work.

    Also, if you have read the calibration we may be able to compare the mask ID with a stock file from a later vehicle to see if it is the same. Same mask id indicates most likely they used the same ecm.

  10. #10
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    OK, digging into more now... Is there a way to analyze the EPROM data I have? Just curious where I would find that data from the chip itself..is there a specific location I would look in the data?

    Great stuff...checking the links now! Thank you for assisting!

    Pete

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    The typical file begins with calibration data. There is a program ID known as the Mask ID which can be found at location $0008. If your chip has a mask ID other than $AA we may be able to determine which program was used. This would be a big step in determining whether or not a stock ecm could easily replace it.

  12. #12
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    I have the file, just trying to figure out how to track it down... I tried an online tool and it couldn't find the mask...poking around in my eprom programmer buffer now to find it...

    Pete

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    Location is the eighth byte after the first. Could be C008, 0008, You could load the definition into Tunerpro with one of the $0E definitions and it will show the mask ID.

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