Dead ECU, 12V on 5V circuit

[ostlar]

Hi!

I've got a 1990 Galant GLSi with a 2,0L 4G63 with the EFI Multi.
This is not a VR4, but I wasn't able to register on The Galant Center, so I will try my luck here.

It was running fine, parked it in the garage, and just a couple days later it wouldn't start at all.
It cranks with no sign of firing, except with starter fluid.

Here's what I've diagnosed so far, in somewhat chronological order:

• It cranks and starts with starter fluid, so spark and air is present, just missing fuel.
• Fuel pump works, good pressure at the rail.
• Sounds like good compression.
• Crank sensor in the distributor works, I get pulses from the hall sensor.
• Injectors are all tested and work individually, but doesn't seem to get any pulse from the ECU.
  They have +12V on pin 1 (on the injector connector), and the ECU grounds them with the NPN transistors.
  These seem to have proper ground, I opened and measured them. Unfortunately I don't have an oscilloscope to check the pulses.
• Sensors like the MAF get power, but at 12,5V instead of 5V in the service manual?
  • This is most likely due to the ECU having 12V at the 5V outputs, more on that further down the list.
• Diagnostics code signal on pin 1 is constantly on, which reads ECU fault.
• Check Engine Light is on, and does not shut off after 5 seconds as it should
• MPI Relay has power and works as it should, checked continuity
• ECU has both power and ground where it should
• ECU looks completely fine inside
• Changed out the capacitors, made sure to clean the board. No sign of leaking from the original caps.
• Measured voltages on the ECU, and I get no 5V at all, only 12V. This is concerning, and according to this tutorial on a Russian site, I should get 5V at the 100µF cap: https://autodata.ru/article/praktika_remonta/mitsubishi_blok_upravleniya/
  

Does anyone have any experience with repairing these ECUs, or any schematics?
It's an MD155679 E2T14474 with the MH6111 E822 chip.
There's also a M9104J 924002 chip that gets reasonably warm. ECU draws 200mA in 12,5V.

There seems to be a fault in the 5V power supply, and my conclusion is that the ECU is toast because of that.
I'm trying to find what could be the culprit for the increase to 12V, if it's the green 5V stabilizer transistor, capacitor, or a short.

I could send it to repair for about $350, but my fear is that it cannot be repaired due to the 12V on the 5V rail?

 

[ostlar]

Update!

Finally got the ECU working, mostly thanks to the Autodata tutorial I linked.
I thought the solder joint under C016 looked fine, but I measured it and didn't find continuity across.
Most likely the capacitor has been leaking a tiny bit down the leg, and corroded away the solder pad on one side, just enough that there's a break:



This is right by the green 5V stabilizer transistor that I talked about.
However, the damage is done, and I have fault on four sensors:

13 - Intake temperature sensor
15 - Idle speed control motor position sensor
21 - Engine coolant temperature sensor
25 - Barometric pressure sensor

I haven't been able to properly test the sensors themselves yet, but I've tried switching over the Engine coolant temperature sensor from my Galant GTi, and I still get the same error after code reset (battery unplugged for >10 sec).
So I think some of the inputs on the ECU is dead.

Anyways, this is progress, and I hope this thread can help others in the future.
The car is at least running, although poorly when it's cold.

Oh and also, go and replace your caps before it's too late!

 

[yubh8tn]

ECMLink charges in 20 minute chunks for repairs. Might try them and maybe it'll be cheaper than $350, although I also doubt that it'll be repairable. That being said, I have no experience with pcb repair and have no idea what i'm talking about

 

[ostlar]

ECMLink charges in 20 minute chunks for repairs. Might try them and maybe it'll be cheaper than $350, although I also doubt that it'll be repairable. That being said, I have no experience with pcb repair and have no idea what i'm talking about

Thanks for the tip! Although I'm located in Norway, so it won't be cheap sending it abroad.
I've found an MD167736 E2T14474 on eBay for about $300, and the Mitsubishi ASA software says it should fit my VIN.
That could be a solution if I can't get mine to work properly. I'm going to contact the seller and ask for a picture of the inside to check if the chips are similar, just to be sure.