Robsevo9 Posted December 31, 2022 Report Share Posted December 31, 2022 Hello, I am having a fuel issue with my evo where the white oem power wire isn’t getting any power to start the fuel pump. I am just going to use the g4x to trigger the relay. Aux 10 and 11 are already being used idk on what previous owner hacked all these wires and I do not want to touch anything. Does anyone know how and where can I connect a wire to trigger the relay for the fuel pump? Quote Link to comment Share on other sites More sharing options...
Adamw Posted December 31, 2022 Report Share Posted December 31, 2022 Only Aux 9 & 10 on the expansion ports can be used as outputs. Can you not use the existing fuel pump control wires - Ign 3 or Aux 12? Quote Link to comment Share on other sites More sharing options...
Robsevo9 Posted December 31, 2022 Author Report Share Posted December 31, 2022 4 hours ago, Adamw said: Only Aux 9 & 10 on the expansion ports can be used as outputs. Can you not use the existing fuel pump control wires - Ign 3 or Aux 12? Thanks for the reply, on the ecu harness I am getting power for that wire that goes into the g4x, a direct wire from the ignition might work but I would need to relay and fuse it. I am trying to keep it oem and not hardwire anything. I’m going to look at aux9 to see if it’s taken up thanks Quote Link to comment Share on other sites More sharing options...
Adamw Posted January 1, 2023 Report Share Posted January 1, 2023 Note the ECU only outputs a ground signal that goes to the fuel pump relay, it does not supply power to anything. It sounds like you are expecting something different? I have stitched together a few pages from the factory wiring diagram to show how the stock FP circuit works in the pic below (click on it for a bigger version). 12V comes from the battery at top right to FPump relay 1, this relay turns on with the ign switch - it is not controlled by the ecu. When ign is on 12V will come out of FP relay 1, pin 1 and supplies 12V to pin 4 on FPump relay 2, when the ECU grounds the Ign 3 pin this relay closes and the fuel pump will run. FPump relay 3 just controls whether the power from relay 2 goes straight to the fuel pump for high speed mode (green route) or through the fuel pump resistor for low speed mode (purple route). Tim M 1 Quote Link to comment Share on other sites More sharing options...
Robsevo9 Posted January 1, 2023 Author Report Share Posted January 1, 2023 13 hours ago, Adamw said: Note the ECU only outputs a ground signal that goes to the fuel pump relay, it does not supply power to anything. It sounds like you are expecting something different? I have stitched together a few pages from the factory wiring diagram to show how the stock FP circuit works in the pic below (click on it for a bigger version). 12V comes from the battery at top right to FPump relay 1, this relay turns on with the ign switch - it is not controlled by the ecu. When ign is on 12V will come out of FP relay 1, pin 1 and supplies 12V to pin 4 on FPump relay 2, when the ECU grounds the Ign 3 pin this relay closes and the fuel pump will run. FPump relay 3 just controls whether the power from relay 2 goes straight to the fuel pump for high speed mode (green route) or through the fuel pump resistor for low speed mode (purple route). Thank you so much! I found out that I do have power at the ignition wire (black and white)#2 but somewhere in the middle it gets lost and my relay isn’t getting that power on #3 for my first relay… and same for the 2nd relay but it has very lil light and my tester is very dim….. here’s the crazy part. The both click when I turn the key to On pos, so somewhere from the ignition to relay 1 pin 3 there’s a short….Previous owner hacked a lot of wires in the car. I was thinking of using pin 21/ing3 as a trigger to my double pumps. Which is the oem output for fuel pump Quote Link to comment Share on other sites More sharing options...
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