kairojya

I have a 97 240sx SE with an early-gen S14 SR. Car was originally an auto, and the person I bought the car from had a shop perform the motor swap. This was years ago...

Anyhow, I recently have done some work to the harnesses as I have bought an AEM Series 2 for this engine. I added in IAT and MAP sensor wiring and removed the stock 02 sensor wiring and MAF sensor wiring. Something I have found that's weird as hell has to do with the fuel pump ...

In the 'original' wiring since the swap, the black/yellow wire from Pin #18 @ the ECU, which is considered "fuel pump relay control signal", was cut coming from my ECU connector. The black/yellow wire in my harness was then butt-connected to an added piece of wiring:



That wire ran over to a junction as shown below (it's the wire coming from the bottom left of the picture next to the red/clear thick wire). From here it split, going up and to the right along with some other GND wires (not sure where exactly this wire comes from, I can verify it tomorrow):



The other wire, as shown below, goes to a group of grounds coming off my F3 plug as far as I could tell.




Now, here is where shit gets gangster as fuck, the other end of the black/yellow wire coming from my ECU connector (it was cut at that end remember) runs along the engine harness to the F3 plug, where it is spliced into a thicker Gray wire at the top right 3 pins down from the top (the thicker part of the plug). This pin itself (on the chassis side of the connector) has 12v with the ignition switch to ON. In effect, 12v is sent through this directly to a chassis ground (with a grouping of other GND wires).

This wire, is a switched +12v from the fuel pump relay on my driver's side footwell. Without it wired this way, my fuel pump does not prime when the key is turned to ON.

Question: Why the fuck would any shop wire this in this way? And how the hell am I supposed to wire it? My AEM Series2 expects to use this pin @ the ECU as an OUTPUT to control my fuel pump relay.

kairojya

So here's some better information. This is the pin on my F3 connector that I was talking about above (spliced into the black/yellow wire, that was then grounded):






This is the relay on my driver's side, and I'm pointing to the pin that runs to the F3 pin I was showing above. The bottom pin goes to the fuel pump I believe, the right and top pins have 12v with the ignition ON. When the relay is connected, the pin I am pointing to has 12v, going over to my F3 which was spliced into a GND wire (wtf?).

b4l

did you fix this already i know this i kinda old