what could cause the ecu not to ground the fuel pump?

[JaredP]

alright, so i put an rb20 into my s13, and did a wire tuck at the same time, trimmed all the useless stuff out of the chassis harness and stuff that i wasnt using. fast forward a few months, had the rb in, wired, fluids in it and ready to go..but the fuel pump wont prime when i roll the key over.

now when i jump terminal 18 on the ecu (fuel pump) to ground, the relay clicks and the fuel pump works just fine but the car still wont work. what could cause this? other random facts that may help:

-lower harness is not hooked up, was jumping the terminals on the starter to try and get the car to start
-car was an auto before, and the park/neutral switch and inhibitor relay were NOT bypassed
-put ecu in friends r32 gtst and his exact words are "your ecu runs my car better than my own" so ecu is fine.
-with fuel pump running, car will still not start. did NOT check spark.
-all accessories ie. lights, horn, turn signals, stereo..pretty much everything i kept in the car after the tuck, still works so im not sure if the chassis wire tuck has anything to do with it
-batt was relocated to trunk

alright, thats everything i can think of. all the wiring is out of the car again as i trimmed some more stuff and actually am working on putting it behind the dash. just trying to figure out what could be the issue

[Boostin240sx]

There are a couple of potential issues, if the ECU is 4 individual connectors use the RB20 side if it is a single plug I think you can use the RB25 side:

RB25 ---> RB20
pin 50 (C/U ground) ---> pin 36/28
pin 108 (C/U ground) ---> pin 107/ 108/ 116
pin 49 (const 12V) ---> pin 34
pin 45 (ign sig from key switch) ---> pin 25
pin 16 (ECS relay ground) ---> pin 40

It uses these to properly engerize the ECS relay. Make sure this relay gets energized. The RB20 harness also uses the ignition signal for the ignition circuit and the injectors directly.

[JaredP]

so my ecu is one large blue connector, so id be looking at the rb25 side of that list? or should i just make sure the ecs relay (the one in the fuse box?) is getting power

[Boostin240sx]

There is a relay in the fuse box that does power the pump but the ECU tells it when to turn on.

The ECS relay is one of the two next to the ECU, make sure they energize.

Sounds as though your connector is the same as a RB25 so I would say yes but you should double check the FSM to be sure.

[JaredP]

alright, i'll make sure both those relays are good when i put all the wiring back. do they turn on with ignition power?