sr20det computer will not send power to fuel pump relay

[sr20det_ute]

hi, ive installed a sr20det into my ute and im running a external fuel pump and its all hooked up to the relay but when i turn the ignition on the fuel pump will not prime or show any life at all. the fuel but works fine as i hooked it upto a power sorce and it ran mint and my engine fired but the fuel pump goes flat out. so the only thing i can think of is the computer is not sending power to the relay? i herd some thing in the computer can short out beacause of this or maybe is has some thin 2 do with the cas? any help would be great

[IanS]

Its possible that the ECU has an internal short causing it not to send power to the relay.

Are you using the Nissan relay/fuse block, or the OE one from the Ford? The relay design may be different causing a normal power on signal not to trigger the relay.

IIRC the ECU should command the fuel pump on to prime any time it is powered up, then it should run it continuously once a signal is received from the CAS.

i would suggest temporarily hard wiring the fuel pump on so you can run the engine. Make sure the engine runs normally. Make sure the ECU isn't throwing any codes. With the engine idling, use a multimeter to check to see if the ECU has power at the fuel pump relay wire. If not, you have a short.

In that case, you could get a new ECU, or just run a toggle switch to the relay.

Good luck.

[sr20det_ute]

yes ive already hard wired the fuel pump and the engine runs normaly but while driving it dyed wen it hit boost but i just think that to do with the fuel pump over fueling because it just goes flatout nonstop, but ill try starting the engine and testing to see if the black and pink wire shows and sign of power but it doent wen ignition is turned on coz ill already tryed. One thing I noticed though before a started the engine was that one of the wires on the cas was broken but lucky i found it befor I started the engine, would that have done anything?

[sr20det_ute]

and also im running a aftermarket relay, I do have a nissan fuel relay though but i just dont know how to wire the nissan 1. and what do you mean by my ecu through codes? how do I know if it is? and wats a toggle switch?

[IanS]

Hahahaha, a toggle switch is just a small switch with terminals that can easily be wired into a car. It would make the fuel pump manual.

The fuel pump should run full out all the time. Any time the engine is running the fuel pump should be flowing as much fuel as possible. Its up the the FPR (Fuel Pressure Regulator), to control how much fuel the engine actually sees.

What kind of fuel pump are you using?

The SR20DET ECUs have an On Board Diagnostic feature. Depending on what chassis and year your SR came from there are different access procedures.

[sr20det_ute]

haha oh ok , but wen I hook the pump up to a power souce and let it run none stop even with the engine goin it sounds like the pump is going to slit the lines of pop one of because it is goin so hard out or is that normal? its a walbro pump. does the enginge its self have a regulator on it because since the engine is not in its original car its now in my ford couior ute and the fuel come straight from the tank through thr filter the through the pump in2 the fuel rail? would I be a good idea to get a aftermaket fpr?

Yea since the sr is in my ute I would not be able to tell?

[IanS]

Ah, it is a walbro. They are very loud. I have an in tank walbro in my 240SX, and even with full interior you can hear it running.

The FPR is bolted to the front of the fuel rail. I would strongly suggest getting a new FPR in the new future. The high volume fuel pumps flow so much fuel that they can overload the spring in the factory unit, causing high fuel pressure. This effects performance, as well as fuel injector life span. There are many aftermarket FPRs out there, but Nismo makes a direct replacement adjustable unit that a lot less expensive than many, and because it replaces the factory one, there is no extra mounting or accesorries required, plus it leaves less clutter in the engine bay.

As for figuring out what engine you have, a picture or two would be very helpful at figuring out. But I might be able to figure it out if you can answer some questions.

You said it has a CAS, this means it is originally from a RWD car, meaning a Silvia or 200SX. All thats left is to figure out what generation it is.

This also means this thread is in the wrong section. This are is for FWD SR20s, we have a specific are for those that were used in RWD platforms. If you would like, I could move it there for you. That area sees a lot more traffic, and you will likely get answers from more than just me.

[sr20det_ute]

oh cool yea even with the ngine running i can still hear it but ive just wired it up to ignition now so I could drive it and its still dying when I hit boost it runs sweet untill the turbo kicks in, ive done a bit of reading and some people had had problems with the MAF? Im not sure were the MAF is on my engine or how to check it but I dont even think its pluged in and I cant see were I could even plug the plug in2 as there is nothing even close to it?

all i know about my engine is that its a 13 blacktop.

yes that would be great sorry I didnt relise

[sr20det_ute]

A MAF isnt the same as a air flow meter is it? sorry if thats a stupid quetion

[IanS]

A MAF isnt the same as a air flow meter is it? sorry if thats a stupid quetion

Thats exactly what it is, MAF is an acronym for Mass, Air Flow sensor.

It it is an S13 blacktop, then pulling the codes is as easy as turning the key on, then turning the little screw on the ECU.

[sr20det_ute]

oh ok so i looked at my ecu and ther are 3 skerws on one side and one on the other whick one do I turn? how do I know if it troughing codes?

[IanS]

There should be a very small screw counter sunk into the side of the ecu. Next to the screw there should be a single red LED. The LED should be lit any time the ignition is on. There is usually also a sticker detailing diag procedure. You have to cycle the screw position, then the light will flash.

Unless you have a Type X blacktop ECU. What ECU do you have, 62, 63, or J4?

[virus77]

the ecu doesn't send power to the relay btw so if you are checking for power on the black/pink you are not going to see any. The ecu GROUNDs the relay which activates it, then the relay powers the fuel pump.

[White Comet]

cut the black/pink wire from the relay to the ecu and ground it separately so it doesnt ground through the ecu

[virus77]

the whole point is so the ecu grounds the relay so it can prime, shut off incase of motor stopping, not spray fuel everywhere in case of an accident when fuel line rupture and motor stalls.... you get the idea.

[kentuckyslider]

the ecu doesn't send power to the relay btw so if you are checking for power on the black/pink you are not going to see any. The ecu GROUNDs the relay which activates it, then the relay powers the fuel pump.

What he said. There are 2 hot wires going to the relay. Check the voltage to them first. They come from the ignition through the multi junction. If they are dead you just need to solder a switchable source to the hot side of the relay. If not then the ECU is not GROUNDING the relay. If that is the case then you need to look at fixing/replacing the ecu.