Resolved 1G Found a kill switch linked to MPI. It's the cause of my issues? (Resolved)

[Malrun]

Issue has been resolved by removing the killswitch and repairing the connection

Car: 90 Talon TSI

This stimmed off of 1 sometimes 3 injectors firing but never 4. Took off the CAS with ignition on and spun it to just one injector firing. Before that Zip tied 4 new injectors into the rail and cranked the car over, firing fuel into a box. 4th never fired. After research I looked at the MPI. I'm going to assume the MPI is smoked due to some damage on the wires. Pictures below

When I flip the switch and turn the car on, check engine light does not come on. Switched back, engine light pops up for 5 seconds and boost gauge goes to center.

I'm going to just replace the MPI, but my questions are:
What's the chance these wires are damaged throughout the harness? I can get a pinout and chase the wires but I'd like to know a little bit more before I dive into this never ending rabbit hole. What kind of test other than continuity to make sure the wires are 100% start to finish? Resistance?
I have a ECMLink V3 that will not connect to my laptop. After research, I'm still 50/50 if it will cause it not to link to the ECU. (No visual issues with the ECM)

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[19Eclipse90]

I’d focus more on the injector for now. While that wiring doesn’t look great, it sounds like the switch is allowing the ECU to power on and the fact you get any fuel to the rail suggests the fuel pump is getting power so the MPI relay is working.

Have you tried swapping the non-firing injector to a different position on the rail (different harness connector) to see if the problem moves with the injector? If it didn’t, it’s fairly simple to check the wiring back to the injector resistor pack and back to the ECU. If the injector issue does move with the injector, then it’s the injector.

This is a thread worth reading and bookmarking: 1G basic ECU MPI relay circuit function

 

[Malrun]

I’d focus more on the injector for now. While that wiring doesn’t look great, it sounds like the switch is allowing the ECU to power on and the fact you get any fuel to the rail suggests the fuel pump is getting power so the MPI relay is working.

Have you tried swapping the non-firing injector to a different position on the rail (different harness connector) to see if the problem moves with the injector? If it didn’t, it’s fairly simple to check the wiring back to the injector resistor pack and back to the ECU. If the injector issue does move with the injector, then it’s the injector.

This is a thread worth reading and bookmarking: 1G basic ECU MPI relay circuit function

I checked the resistor pack yesterday and they read 5.6-5.8. Injectors have continuity back to the ECU. I also checked if the one wire was getting voltage from the battery and they were.

Ok, A lot going on in that link. I'll try to repair the wires at the MPI and starting working from there.


The car runs after the repair to the MPI!

 

[19Eclipse90]

Glad to hear! And thank you for following up to let us know!