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Bypassing ignition module on coiplacks?

EFI Wiring Fundamentals

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Discussion and questions related to the course Motorsport Wiring Fundamentals

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Good day

I hope someone can help. iv been battling with my GTO/3000GT for long time now.

i have a stand alone ECU in it but for some reason i cannot get the Coils to fire. everything else works. i have checked every single inch of wiring and diagrams and voltages and continuity and the things still wont work.

the coilpack needs to get 12V from Supply, earth connection and then signal. the Ignition module and coilpacks definitely work as they are all new.

so from my understanding the Coilpack should receive 5V from ECU as signal and then the transistors work their magic and the coils should fire. but they dont. everything is correct the relays and fuses are correct everything works except the coils and i cant figure out why and no one i know can figure out why and the technicians also cant figure out why nor can the ECU supplier figure out why.

possible issues could be:

the ignition module receive 5V+ from ECu to itself OR the Ignition module must earth to ground to complete circuit and make the coil fire. its currently set to Earth to ground as per manufacturer recommendation.

alternatively, since i know there is 12V+ on the system so i could perhaps take the signal wire directly from each of the 3 coil packs (1&4 2&5 3&6) and bypass the Ignition module and that should make it work right? this requires 12V+ from battery positive to pass through coils and then into the ECU directly where teh circuit is earthed. That does not sound right or safe.

I am really out of ideas here. any input will be appreciated. thanks

Car in question:

1991 Mitsubishi GTO

3.0 V6 6g72 N/A

4spd ATX AWD

ODO: 52 170 km

You've provided a lot of information, but no details on the standalone ECU. What brand / model? Is it setup for external ignitors/smart coils or is it counting in inductive coils (some ECU have build options so you need to be using the compatible version).

What does the 5V signal to the coils look like? Is it rising edge to charge, and falling edge to trigger? What did the OE Ignition System do?

What does the trigger going to the Ignition Module look like? Is it falling edge to charge, rising edge to trigger?

It sounds to me like you have an external ignitor (the ignition module), and are trying to use that with coils that have a build-in ignitor. Assuming the ECU is configured for external ignitor, then I would go straight to the coil triggers, without the ignition module.

I can't believe the ECU manufacturer can't help you sort out a working ignition system, or recommend an example of something that works with the ECU.

ECu im using is a Spitronics Orion 2... i think its an unkown brand on teh global scale so didnt mention it.

the main issue is that the GTO here is not a very well known car. people have no idea what it is or how it works. So the suppllier does not have a lot of experience with it. they run it off the colt v6 which is not the same even though its the same engine. Those engines in the colts run with distributors and are SOHC. the entire ignition system is void on the colt. The problem is my car is unknown. Thats why im thinking the ignition module is the issue cause the other cars dont have that.

This car hasnt driven since 2019 and i know im so close its one little wire or something small that im missing here. there are at least 2 other GTO owners whose cars got scraped. no one has managed to solve the issue. they got to the same issue as i have now.

To be fair my supplier have supplied me with all the information iv asked for. Their technology is working the issue is making it work on my car.

I even get a signal for firing form the ECU at 12deg BTDC. I know its working and believe the issue is the wiring. mainly the ignition module.

but im scared if i take those wires straight to the ECU bypassing the ignition module it could damage the ECU.

i cant seem to find information on ow to wire the GTO. it sounds straight forwards but it isnt which means there is a parameter i do not know of.

how the GTO coils function with factory system:

everything is powered up on startup. its all controlled by MFI relay this activates the fuel pump the injectors coils CAS TPS and AFM.

focusing on ignition system 12V is applied to the coils. 3V is applied to pin 3 (coil 1) and th transistor earths at pin 4. 12V flows through pin 6 and pin 13 (coil 1). all 3 coils are charged up and then by earthing pin 1 2 or 3 to pin 4 (the earth) the coils fire. i have attached image. as i find the transistors confusing.

how Stand alone ECU works

ECU activates 4 pin relay with 12V (85+86). Then power goes to all coils (87 +30). ECU earths the required signal wire creating a spark.

Attached Files

here is a diagram on how to test a Power transistor unit or ignition module.

Attached Files

here is the diagram the ECU manufacturer gave me... the instructions are very clear.

Attached Files

Do you have the 3.0L twin turbo model with the 6G72?

The Misubishi GTO/3000GT has an external ignitor in the factory configuration. They run a 3 channel ignitor from factory, which has 2 plugs, one with 3 pins and the other with 6/7

If your ECU can run your coils directly, as it contains an inbuilt ignitor assembly, you should be able to wire them like your colt v6 diagram.

If not, you need an ignition module to be fitted (like the factory unit, or an aftermarket one). Chances are if you have been trying for long enough to run these coils without a required ignitor, you may have damaged the ignition driver circuitry on the ECU.

Yes thats the one

I phoned the supplier again and they said the ECU can handle the coils directly. The ECU can handle it. I think this should do the trick.

so im gonna do that today and hopefully the car will start up for the first time since May 2019.

UPDATE:

its working now. \8D/

so if anyone ever has issue with 3000GT or GTO with a stand alone system. remove the ignition module.

Thank you for all the help