Page 1 of 2 12 LastLast
Results 1 to 15 of 30

Thread: GM MEFI Computer / Crate 502 Engine Computer

  1. #1
    Super Moderator dave w's Avatar
    Join Date
    Feb 2011
    Posts
    6,268

    GM MEFI Computer / Crate 502 Engine Computer

    I'm wondering if anyone has information, links, write ups, or internet form posts about the GM MEFI computer used with a GM Crate 502 engine?

    I've found MEFI Scan & Tune, which really stresses the budget. http://www.aldlcable.com/sc/toplevel.asp?cat=32.

    I'm hoping to find wiring schematics, and how to pull trouble codes. The engine is up and running, but very poorly. Maybe something is wired wrong, but without schematics I don't know. I'm thinking I need to wire a SES light? I'm trying to figure out how to pull trouble codes, without an expensive scan tool.

    Thanks,

    dave w

  2. #2
    Fuel Injected!
    Join Date
    Apr 2013
    Posts
    121
    You didn't mention if this was a friend or a customer ... so some varying options are available.

    If it is a friend ... then perhaps a referral ... high-end marina's or custom boat builders often have MEFI tuning software.

    If it is a customer ... the easiest course of action for you is to treat this as an 0411 swap (just like with an older Vortec truck). The 502 as the plastic front timing cover - but the CKP hole will be plugged (or solid). Add a 4x CKP reluctor, CKP sensor, a Vortec style distributer, rework the wiring harness, and you are good to go.

    The resultant tune will be 100% custom, but if you have a WBO it shouldn't be a problem. If you have a RoadRunner even quicker to do.

  3. #3
    Super Moderator dave w's Avatar
    Join Date
    Feb 2011
    Posts
    6,268
    Quote Originally Posted by Buzz View Post
    You didn't mention if this was a friend or a customer ... so some varying options are available.

    If it is a friend ... then perhaps a referral ... high-end marina's or custom boat builders often have MEFI tuning software.

    If it is a customer ... the easiest course of action for you is to treat this as an 0411 swap (just like with an older Vortec truck). The 502 as the plastic front timing cover - but the CKP hole will be plugged (or solid). Add a 4x CKP reluctor, CKP sensor, a Vortec style distributer, rework the wiring harness, and you are good to go.

    The resultant tune will be 100% custom, but if you have a WBO it shouldn't be a problem. If you have a RoadRunner even quicker to do.
    It's potential customer ... I'm wanting to pull trouble codes if possible. If I can't pull codes, I might as well leave with my tail between my legs.

    0411 swap seems like a distant option at this point in time.

    Thanks,
    dave w

  4. #4
    Fuel Injected!
    Join Date
    May 2011
    Location
    Pocono's PA.
    Age
    50
    Posts
    370
    Quote Originally Posted by dave w View Post
    It's potential customer ... I'm wanting to pull trouble codes if possible. If I can't pull codes, I might as well leave with my tail between my legs.

    0411 swap seems like a distant option at this point in time.

    Thanks,
    dave w
    Dave ,

    I have sent a few emails / texts to some people I know in the Marine field who might / might not deal with this.

    If I can come across something I will report back.

    TOM
    1994 3500 Dually , 502 (509) , 264HR , Edelbrock MPFI , PFI '7427
    1992 S-10 434 SBC/Tremec - '7427
    1986 Monte Carlo SS
    1984 S-10 , SAS, 496/700R4/205 , D44/14BFF -'7427
    1980 Z-28 496/700R4
    1979 Corvette 496/700R4
    1977 Olds 98 Regency 403/700R4

  5. #5
    Super Moderator dave w's Avatar
    Join Date
    Feb 2011
    Posts
    6,268
    I found this link: http://www.pirate4x4.com/tech/billavista/MEFI/

    Has information for Trouble Codes.

    dave w

  6. #6
    Fuel Injected! roughneck427's Avatar
    Join Date
    May 2012
    Location
    Fresno CA
    Age
    48
    Posts
    271
    Lyndon from westers had mentioned i forgot where on a forum that the interface is the same as the obd1 LT1 i was going to make a crossover connector to use on a mefi aldl setup but the guy never got back to tune it so i never pursued it. I did find some schematics online on some marine forums for the data wire and whatnot on the mefi aldl. I know on efi live forum a guy was building a def file to scan with efilive V4

    http://forum.efilive.com/showthread....efinition-file

    http://www.marinepowerusa.com/download-delphi-mefi.php
    Last edited by roughneck427; 01-25-2014 at 12:19 AM.

  7. #7
    RIP EagleMark's Avatar
    Join Date
    Feb 2011
    Location
    North Idaho
    Age
    63
    Posts
    10,477
    I think they come with TunerPro RT definitions, so who ever bought that system should have the files needed? Cable is another story...

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
    -= =-

  8. #8
    Administrator
    Join Date
    May 2011
    Location
    Lakes Region, NH
    Age
    54
    Posts
    3,847
    Dave...

    I had MEFI 2 in my Chevelle. I have some info. I have some software. I have some wiring diagrams.

    Here's a page from my old site with info to get codes from MEFI 1 and 2. Might work with MEFI 3, 4, 5. Learned much since that page was put up.

    lmk if this works. lmk which version of MEFI.
    http://www.grolen.com/shannen/efistuff/

  9. #9
    Super Moderator dave w's Avatar
    Join Date
    Feb 2011
    Posts
    6,268
    Quote Originally Posted by 1project2many View Post
    Dave...

    I had MEFI 2 in my Chevelle. I have some info. I have some software. I have some wiring diagrams.

    Here's a page from my old site with info to get codes from MEFI 1 and 2. Might work with MEFI 3, 4, 5. Learned much since that page was put up.

    lmk if this works. lmk which version of MEFI.
    http://www.grolen.com/shannen/efistuff/
    Thanks 1project2many!

    The question I have is about what to use for a MIL. Do you have manufacture / part number that will work with MEFI?

    Maybe the LED light I've been using for a MIL with the '0411 PCM will work with the MEFI? http://www.k-four.net/Product.aspx?pid=68

    dave w

  10. #10
    Fuel Injected!
    Join Date
    May 2011
    Location
    Pocono's PA.
    Age
    50
    Posts
    370
    Here are a couple of links I was forwarded . Marine based , but might be of some help

    http://www.boatfix.com/merc/techbk/96/96hgd4.pdf

    http://www.michaelstractors.com/foru...p?TOPIC_ID=199

    HTH

    TOM
    1994 3500 Dually , 502 (509) , 264HR , Edelbrock MPFI , PFI '7427
    1992 S-10 434 SBC/Tremec - '7427
    1986 Monte Carlo SS
    1984 S-10 , SAS, 496/700R4/205 , D44/14BFF -'7427
    1980 Z-28 496/700R4
    1979 Corvette 496/700R4
    1977 Olds 98 Regency 403/700R4

  11. #11
    Administrator
    Join Date
    May 2011
    Location
    Lakes Region, NH
    Age
    54
    Posts
    3,847
    I used an expensive test light from Snap-On. It's only about $30!!!

    The LED should work. So should the same #194 bulb that's used in most dashboards. Even a low impedance light will work if you put some resistance in series.

    My understanding of MEFI3 and up is that when the calibration is password locked it can't be read without the same password, although it can be overwritten at any time. I have a single calibration here for a 502 from a MEFI 1

    MEFI controllers that I've tuned are different than automotive counterparts. They don't bother calculating airflow or AFR. You enter the desired injector on time based on MAP and RPM. The MEFI 1 BPW vs MAP and RPM table begins at 40 kPa and goes to 100 kPa in 20 kPa increments. There is not as much resolution for tuning. There are several safety switch options such as engine overtemp, low oil pressure, low coolant flow, and emergency stop that can all affect your success. MEFI controllers are able to use O2 sensors in closed loop and can receive input from a VSS. They also use a trim sensor although I have never considered how that affects off-water use or how it can be modified to help road going applications. AS&M used to charge big money to "convert" an open loop cal but as most of use know, there isn't much involved in flipping a bit and adjusting a temp setting or two. The big thing they offered was the schematics to connect the sensor. Again, this may not apply to MEFI 4 and 5.

    In the 1 and 2 controllers, code is stored in the controller and only calibration data downloaded / uploaded for adjustment. I'm told the upload/download process is very similar to programming an OBDI LT1 or the 92-94 Cavalier 2.2 with manual trans. I'll upload some calibration data I have for a specific MEFI1 calibration as it should be with the caldocs data. This info could be used to make a very complete TP definition file.
    http://gearhead-efi.com/caldocs/MEFI9321.pdf

  12. #12
    Administrator
    Join Date
    May 2011
    Location
    Lakes Region, NH
    Age
    54
    Posts
    3,847
    Here are some additional documents that apply to MEFI. The Mercruiser scan tool manual gives trouble codes and scan tool functions for anyone attempting to make an ADX for TunerPro. The two .jpg images are wiring connections for MEFI 1 and 2 showing, among other things, the connection points for an O2 sensor (J2-16 is LOW and J2-17 is Signal). Once upon a time, you could download TTS scantool software for MEFI. I don't know if it's currently available or if it works with other ecm's but it did allow a free trial period.
    Attached Files Attached Files

  13. #13
    Super Moderator dave w's Avatar
    Join Date
    Feb 2011
    Posts
    6,268
    I visited with the MEFI 502 vehicle owner yesterday (56 Cadillac). I thought I'd share some pictures. The computer is either MEFI 3 or MEFI 4.

    Thank you to everyone who helped me with information!

    I found two trouble codes, 34 & 81. I found the wiring for the stand alone 4L80E TCU was not correctly spliced into the MEFI harness (5 volt reference). The engine runs, but the idle is 2800 ~ 3200 RPM's! I need better diagnostics. Maybe the MAP or TPS was fried with the incorrectly wired 5 volt reference.

    I used one of the high speed printers from work to print the 300+ page .pdf files (2 minutes 14 seconds print time for double sided print) and gave printed pages to the Caddy owner.


    dave w
    Attached Images Attached Images

  14. #14
    Administrator
    Join Date
    May 2011
    Location
    Lakes Region, NH
    Age
    54
    Posts
    3,847
    Wow... That's a nice looking project.

    I have a copy of the free-to-download version of TTS Datamaster if there isn't one currently available. I've never tried it but if you need a copy lmk. There used to be a copy of the converter circuit used with the Diacom software. You can build simple circuits well enough... Old software works on DOS / LPT port if you have a machine that can run it.

  15. #15
    Fuel Injected!
    Join Date
    May 2011
    Location
    Pocono's PA.
    Age
    50
    Posts
    370
    Quote Originally Posted by dave w View Post
    I visited with the MEFI 502 vehicle owner yesterday (56 Cadillac). I thought I'd share some pictures. The computer is either MEFI 3 or MEFI 4.

    Thank you to everyone who helped me with information!

    I found two trouble codes, 34 & 81. I found the wiring for the stand alone 4L80E TCU was not correctly spliced into the MEFI harness (5 volt reference). The engine runs, but the idle is 2800 ~ 3200 RPM's! I need better diagnostics. Maybe the MAP or TPS was fried with the incorrectly wired 5 volt reference.

    I used one of the high speed printers from work to print the 300+ page .pdf files (2 minutes 14 seconds print time for double sided print) and gave printed pages to the Caddy owner.


    dave w
    Wow , that's sweet

    TOM
    1994 3500 Dually , 502 (509) , 264HR , Edelbrock MPFI , PFI '7427
    1992 S-10 434 SBC/Tremec - '7427
    1986 Monte Carlo SS
    1984 S-10 , SAS, 496/700R4/205 , D44/14BFF -'7427
    1980 Z-28 496/700R4
    1979 Corvette 496/700R4
    1977 Olds 98 Regency 403/700R4

Similar Threads

  1. 454/4l80e/203/205 - Which computer and harness?
    By caddyrodder in forum GM EFI Systems
    Replies: 2
    Last Post: 08-19-2013, 07:59 PM
  2. Is my computer shot?
    By volkerc in forum GM EFI Systems
    Replies: 40
    Last Post: 06-06-2013, 12:13 AM
  3. need computer
    By cooterb78 in forum Buy - Sell - Trade - Wanted
    Replies: 2
    Last Post: 03-28-2013, 06:40 PM
  4. New computer, got questions
    By JeepsAndGuns in forum Gear Heads
    Replies: 9
    Last Post: 01-06-2013, 02:58 AM
  5. I put Fuel Injection on my Computer
    By EagleMark in forum Gear Heads
    Replies: 0
    Last Post: 03-17-2011, 07:40 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •