GM MEFI Computer / Crate 502 Engine Computer

[EagleMark]

I think they come with TunerPro RT definitions, so who ever bought that system should have the files needed? Cable is another story...

[1project2many]

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/

[dave w]

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

[Nasty-Z]

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

[1project2many]

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

[1project2many]

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.

[dave w]

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