Resolved 2g It completely cut out, MPI relay is clicking fast

[okm12346]

So I've never had any problems with the wiring, but the other day got really cold (-15) and the car didnt wanna start. It cranked but no start. I popped the hood, moved some ground cable around and it started. As I drive down the road, about 1 mile from the house, it completely cuts off and it dies. Dash lights and all still works. Tried to start it and nothing. I get this fast clicking from the MPI relay and no start.

CEL is on, OBD scanner and ECMlink do not want to connect.
It doesnt do the 8 sec delay after the key has been turned off.
The relay from the fuel pump rewire clicks along with the MPI relay.
TACh is bouncing at around 1k whe i turned the key on.
Changed the CAS (1g)
Redid all ground wires.
ECU looks good, no burnt circuits or leaky caps.
TB doesnt have an IAC.


Im charging the battery right now and I'll test it again. Im about the change the ignition key as well


Any suggestions are appreciated

 

[AllanL]

if your ecu is e-prom'd, any chance it's gotten loose from the e-prom socket?

 

[renovatdkitchen]

I had a similar problem back with my first Talon.

Try checking the wires around the ECU and ensure its getting a good ground. Then open the ECU, check for loose eprom (as said above), as well as for burn marks on the main board or any bad smell. I believe mine ended up being a faulty board.

 

[okm12346]

pins 13 and 26 are the ground pins for the ECU, correct?

I inspected the ECU board and pulled the EEPROM out. Everything looks normal, no leaky caps.

 

[okm12346]

so I disconnected all 12v plugs in the engine bay. No difference.
Pulled the the Fuel pump harness plug out - no difference

I started testing the ECU pins for voltage:

Grounds 13,26 - good
Power +12V 12,25 - good

Now where I have an issue with.

Fuel pump relay is controlled by pin 8.
MPI relay is controlled by pin 38.

When pin 8 wire is connected and I turn the key the ECU disconnects completely. IDK if this would be the correct term to use. In other words, from having 12V on pin 38 with key off, it drops to zero with the key on, and the fuel pump relay starts buzzing.

When I pull pin 8 out of the plug, I can cycle the ignition key on and off pin 38 always stays at 12V and the fuel pump relay doesnt buzz.


Again, the ECU doesnt have any visible cap leakage or burnt circuitry.

How possible it would be if the chip lost its ROM?

 

[luv2rallye]

MPI relay always has +12v on the other side. This side which connects to pin 38 is pulled to ground (0v) by the ECU to turn the relay on. So when the key is off (ECU off), pin 38 will float to +12v.

Fuel pump (FP) relay has +12v on the other side when ignition key is in ON or START. This side which connects to pin 8 is pulled to ground (0v) by the ECU to turn the relay on when the ECU is completely powered up (and key is ON or START). The ECU only powers up when MPI relay is on and it passes it's internal power on tests. When the key is in OFF (ECU off), pin 8 will read 0v since no voltage is on other side.

 

[okm12346]

Just to follow up on this, the ECU was a toast, not sure where exactly tho. Still cant see any damaged components or circuits.

Just received another ECU in the mail and she fired up.

Thanks for your help!