No ECU power. MFI Relay Help

[Kyogie12]

Been searching around and couldn't find specific help for my issue.

This is on a 97 GSX that just finished a rebuild. Went to connect the battery last night to start it up and break it in and my roommate connected the ground terminal for the battery to the positive post. That blew the 100amp Alt fuse in the hood. I had the MFI (motor) fuse pulled to prime for oil anyway. However there is no CEL on acc key turn. Checked the ecu and nothing looks burnt (95 eprom with ecm link). However i'm not getting power from pin 12.

This lead me to believe this blew the MFI relay out. I've found info on the 95 relays and how to test. But this being a 97 it has the two mfi and fp relays next to each other. Just wondering if anyone had specific info on how to test that mfi relay and see if I can restore power to the ECU.

Thanks. Other thoughts on what else might have blown out would be appreciated too.

 

[92AWDHX40]

http://www.dsmtuners.com/forums/tun...6496-fuel-pump-power-mpi-mfi-relay-issue.html

How to Check MPI Relay (DIY DSMers)

try these

 

[Kyogie12]

Found both of those earlier. Those are for the 95 relay. I need the 97 where it's two 4 pin relays. One is FP other is MFI.

 

[92AWDHX40]

I would ask steve he would probably know.

 

[Kyogie12]

What's his username?

 

[92AWDHX40]

steve hes on here from time to time the wiring guru.

 

[Kyogie12]

Nice update. I have power again to the ECU, MPI and FP relay are good now. All fuses good. Took another look at the ECU and I blew the track at D103. Just the track though, the black electronic component (can't remember what its called right now) is fine.

So i'm on the hunt for a new eprom ecu. Last question is do you think that blew out the ecm link eprom chip? I'm really hoping all I need is just a new socketed ecu, and not have to buy link again....expensive :/

Final update.

I was able to resolder the track at d103 (pin 12 for power) and got the ecu back online. I really lucked out with this one. Also the ECM chip was fine, car was tuned quickly and start-up went great!

 

[erkitner]

Looks like you got lucky, there. I wasn't so fortunate. Diode 103 was blown and the adjacent track was in tact on mine. Blown ECU altogether due to idiots who tried to jump start my car and reversed the polarity. In situations like this, the ECMTuning chip is fine.

Good to see you got it fixed.

 

[redi4axion]

Question, did you have the key in the ignition when the battery was hooked up backwards?

 

[erkitner]

Ahem. No. "I" did NOT. My car was being moved across the country and they didn't see the note I left by the ignition that said, "my car has a "push-to crank" button in the center console". Bastards missed it and figured I had a dead battery. Fried my whole system.

 

[redi4axion]

Oh ok so "THEY" still had the key in the ignition when it was hooked up backwards. The ECU is unharmed with a reverse battery hookup unless the key is in the ignition. Usually when the D103 is blown from that or in general the ECU is done. But my initial question was directed to OP but I should have quoted him to not cause confusion.

 

[Kyogie12]

Oh ok so "THEY" still had the key in the ignition when it was hooked up backwards. The ECU is unharmed with a reverse battery hookup unless the key is in the ignition. Usually when the D103 is blown from that or in general the ECU is done. But my initial question was directed to OP but I should have quoted him to not cause confusion.

Sorry I haven't been on here in a while. I bought a Miata for a toy car and have been working on that a lot lately.

The key was not in the car. It was the last hook up during the engine rebuild. When we went to crank we were very confused why there was no fuel pressure. Which lead to figuring no CEL > bad ECU > blown track.

pm me if ya want some more details.