MEFI 3 to 4 Conversion-repin

E

eaton1989

Recruit
Joined
Jan 21, 2020
Messages
3
I have a 2000 Tige with a 98 Merc Mag 5.7L MPI EFI. I am replacing MEFI 3 with a 4 unit. I can not find repin information for several of the circuits. I have been looking for days. I know this used to be done often but cant find the info. Most links do not work anymore. I do not want to purchase a conversion adapter harness. I think this is a much cleaner way not to mention way cheaper. I have several 3 and 4 pin outs but I need specific circuit information location. The MEFI 4 will be sent out for reflash for this motor.

98 5.7L Merc MPI EFI with Merc distributor (2 wire-thunderbolt IV I think) and 2 wire coil (typical old style coil)

Current questions for repining.

MEFI 3 has 2ea 5v references used by TPS-FPS (J2-4), MAP (J2-19). MEFI 4 shows one location J2-2. Can all three be linked together and connected to J2-2 on MEFI 4? Thats the way one of the pin outs I have seen indicates

MEFI 3 has a J2-10 Distributor reference circuit (430 ppl/wht). Not known where to pin on MEFI 4

MEFI 3 has a J1-2 IGN coil circuit (121 white). Not know where to pin on MEFI 4

MEFI 3 has a J2-20 Load anticipation circuit (208 BRN). Not known where to pin on MEFI 4

MEFI 3 has a J1-26 Audio warning circuit (29 DRK GRN). Not know where to pin on MEFI 4. Is it to J1-8 Buzzer circuit?

All pin outs seen have shown MEFI 4 with a different distributor and coil set up (GM EST distributor). This distributor was included in the version of motor combo for the year along with the thunderbolt IV. Its shown on the parts list both ways for this engine but the thunderbolt has a simple 2 wire connection vs the 4 wire on the EST. All others pins are believed to be known locations.

Im sure this information has been discussed before but a search came up with either 2 options or another came up with over 700. I looked for awhile but I am not getting what I need to finish the repin. So I need someone to point me right if possible.

Any help would be appreciated.

Thanks
 
E

eaton1989

Recruit
Joined
Jan 21, 2020
Messages
3
Thanks for the response/links. I have seen both of these when searching. I used the BillaVista article for most information. This is why I asked. The circuits above in first post are different than in the article. It is using different style distributor. Also showing cam sensor-crank sensor-8 coils etc. Page 175 of the manual with wiring schematic 6 of 9 for the 5.7 shows this. It has a wiring detail that is more involved. I basically have 4 wires on the coil and distributor for my engine and only 2 currently go to ECM. Im not certain but maybe I need to change to a different distributor and coil for this set up/MEFI 4?
 
alldodge

alldodge

Moderator
Staff member
Joined
Mar 8, 2009
Messages
43,326
There has been a couple which tried to change pins on OSO and the last write up was something like
had an expert rewire the connectors and when motor was first fired it filled the cylinders with fuel, so we bought the conversion cables
Click to expand...
 
S

scoflaw

Ensign
Joined
Jun 2, 2010
Messages
962
That conversion cable was NLA 2 years ago. when I was looking for 1.

AS&M will repin your harness and reprogram the MEFI-4
 
E

eaton1989

Recruit
Joined
Jan 21, 2020
Messages
3
I will look into AS&M. I really don't think its necessary to buy a $450 cable. That's $90 per remaining pin (5) locations. Harness is still available from GM I believe as well. They used on the RAM JET Engine for same reason 3 to 4 conversion. They also sale a complete MEFI 4 unit and wiring upgrade for $980. includes some additional sensors.

Thanks for the reply's so far!
 
You must log in or register to reply here.
Top