1995 Mighty Max 1G ECU Conversion Help Needed

[JJCross1994]

I've been fighting this for a while and I'm so close to being done. Any help is appreciated!

Basically I've wired a 1992 1G Turbo ECU into my 1995 Mighty Max running a Turbo 4G64 8V setup. I'm using factory distributor with the 1G CAS trigger wheel in the base. I'm on a dual coil setup with appropriate PTU. I have re-pinned my factory ECU harness to match the 1G and the MPI relay.

I have spark, crank signal, RPM signal, and injector pulse on the scantool. Base timing is set @5⁰ TDC w/ light. The problem is even though the ECU is showing the injectors are pulsing, it's not actually grounding the injectors. Verified harness is good and appropriate wires match in the ECU connector. Verified all chassis ground and ECU grounds are good. I do not have the resistor box wired in yet (sitting on my tool box), but unplugged from the injector I still get nothing on a noid light, even though the ECU says they are suppose to be firing.

Only fault code is for the knock sensor (haven't added one yet). I'm using the truck TPS/ISC. I haven't quite figured out where Pin #2 on the trucks stepper motor for ISC should go in the ECU pinout as I'm not aware of it's a 12V, 5V sig/ref, or ground wire. I had to remove it from it's original slot to make the sensors ground pins match the 1G ECU. TPS and Stepper motor are reading on the scantool as well though.

I'm lost here.

Update: Just looked over my notes for the 100th time and I forgot to add pins 63&66 to the ECU to the MPI ground circuit. I'm guessing this may be my problem? Anyone know what 63&66 actually control?

 

[steve]

https://www.dsmtuners.com/threads/1g-basic-ecu-mpi-circuit-function.435961/

Those are the pins the ECU uses to activate the power side of the 1G MPI relay.

 

[JJCross1994]

https://www.dsmtuners.com/threads/1g-basic-ecu-mpi-circuit-function.435961/

Those are the pins the ECU uses to activate the power side of the 1G MPI relay.

hmm. Well the MPI relay is functioning properly without them it "appears" considering I have everything working but the ECU actually pulling ground to pulse the injectors.

 

[steve]

If things are working without 63 and 66 being connected it appears you have something wired incorrectly. Perhaps you have Pin 8 of the MPI relay connected to ground so it's always on?

How are you powering the injector connector since you haven't wired the injector resistor in yet?

 

[JJCross1994]

So the trucks do not use a resistor box. I was running off the stock ECU temporarily with the 550cc's until I wired in this 1G ECU with the box. Power from injectors comes from the MPI relay.

And that is correct. Being the truck is an 8 pin relay I just swapped the ground (originally pin 7) to pin 8.

 

[steve]

So with the injector unplugged you should see battery voltage on one side and nothing on the other.
With the injector plugged in you should see battery voltage on both sides until the ECU tries too fire it when it should go close to ground. You should see the same thing at each of the 4 ECU pins four the injectors. These measurements expect key on engine off and again while cranking.

It's been too long for me to remember from the ECU code if the scantool reports IPW's it would use or the actual IPW while actually trying to fire one. The difference being some condition disabling actual process while reporting that it thinks there should be activity.

A bit of speculation since I don't know offhand what's causing you issue.

* Correction *
I'm reminded that the circuit in the ECU for the injector drivers also sits at battery voltage when it's not trying to fire the injector so one would see voltage on both pins of an injector at rest.

 

[JJCross1994]

So I actually get 12V on both sides of the connector with it unplugged, which I thought was odd. With the injector unplugged I do get the Code 41 (If I remember correctly) for the injectors. So the ECU is aware if there is a direct issue with the injectors, but for some reason still does not pull them down to pulse.

 

[turbotom]

I recently bought a 92 Mighty Max with a 4g64 2.4 SOHC and I have a spare ECMLink v3 I would like to put in because I do have a CEL and I'm not sure why. My buddy let me use his scan tool but for some reason would not communicate to the ECU. I tried to find a pinout of the Mighty Max but can't find nothing at the moment.

Keeping the truck NA and stock for the most part but would like the comfortability to use my laptop to check for CEL. Could I use whatever the truck has or I have to change things around? Keep it stock so honestly no need for DSM injectors or a knock sensor, it does have a 2g style MAS. If anyone can help me out, that would be great.

 

[19Eclipse90]

These are from https://charm.li/Mitsubishi/1992/Pickup 2WD L4-2350cc 2.4L SOHC/Repair and Diagnosis/

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I also feel like I was able to get some manuals from https://www.mightyram50.net/vbulletin/forum.php but cannot confirm right now.