Fuel Pump Wiring

ok so i just bought a in tank 255lph pump for an s13 240. it has two wires. does anyone know the stock wiring for the pump. and how to set it up.

On the chassis side of the fuel pump connector, there is a BLACK/RED wire that has 12V when the key is 'ON.' You can either:

1) Cut and connect the other lead wire of the pump- its on the opposite end of the same connector from the BLACK/RED wire- to a ground source, and leave the end running into the chassis harness DISCONNECTED ( this WAS the ECU direct control, which the computer may burn out if you try and attach the ground side of the pump to it ).

This will result in the pump running anytime the key is ON, vs normal operation, where it starts and runs for a few seconds and then shuts off. In an accident, the pump may continue to run with the engine off, whereas normally the pump would cease.

2) RUN and ADDITIONAL fused power wire back to the rear of the car. Using the stock BLACK/RED wire on the chassis side of the fuel pump connector, install a relay using the BLACK/RED as the switched leg and the NEW wire for the +positive side of the fuel pump, and ground out the other side as in option#1.

This will again cause your pump to run anytime the key is in the 'ON' postion.

Because of the current draw, I highly recommend option#2.

(IMG:http://i232.photobucket.com/albums/ee276/Sterlingps12/wiring/fuelpumpconnectormod.jpg)

Your wire colors may vary. CHECK WITH A METER TO MAKE SURE WHICH IS 12V! (IMG:style_emoticons/default/wink.gif)

This is for installation in a stock-motored S12.

Ask more questions if necessary.

so sterling with my ka if i wire like #2, add the relay and such then connect the ground sided control to the ecu trigger for the fuel pump, will it work like stock. isnt it the ka that controls the fuel pump from the ground side? or is that the ca?

This post has been edited by silvia love: Dec 15 2008, 09:45 PM

so basicly there is no easy way to do this conversion? if i have to re wire it than idk. could the stock 190lph handle an sr20det?

DatsmO @ Dec 15 2008, 06:54 PM so basicly there is no easy way to do this conversion? if i have to re wire it than idk. could the stock 190lph handle an sr20det?

It could handle a stock SR, you could always wire it to a switch but that sucks sometimes

DatsmO @ Dec 15 2008, 07:01 AM
ok so i just bought a in tank 255lph pump for an s13 240. it has two wires. does anyone know the stock wiring for the pump. and how to set it up.

ya i got a megan racing one

How much did it cost/where did ya buy it?

its really cheap only 80 shipped has 0 to 100psi ajustment. i got it at frsport

ya if you can detail i bit more that would be sweet. the fuel pump i bought has a clip for it that has two wires a black and a red + and - i would assume. so how could i run this to work for normal operation if possible and if i have to do a switch which i dont really mind at all what ever is best to run with and simple.

200sxkitcar @ Dec 16 2008, 01:48 AM
Just start a new thread if you want the details for any S13 swapped engine in an S12 if you want to add a walbro, I have pics and everything ready to roll.

Arro @ Dec 16 2008, 02:03 AM
a 255? If you put in this pump, you will need to run a NISMO or AFR aftermarket fuel pressure regulator, because I'm sure even the stock SR FPR will be overrun by a 255lph unit.

Yours might be healthier than another person's. And I said might. Yes, OEM fuel pressure regulators have weak stock springs, and are not designed to receive the kinds of pressures that a 255lph fuel pump delivers (given it's wired up properly). I can't say *all* or any Nissan will have this problem, but I know of two independent car platforms that have this issue, both are two completely different manufacture (Mitsu and Toyota).

Also, you may say "no problems", but you might not realize that your FPR is being slightly overrun.

I took this from another forum...
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Any 255 does in fact need a AFPR. I have the datalogs to prove it. The 190 does as well but in a very minor way. You can certainly run it without a AFPR. So what you read on Talk is correct, but you can much more easily get away on a stock reg with the 190 than with the 255.

A bit more info on the 255 vs 255 HP. The HP version is capable of flowing more at High Pressure, hence the name. At idle, there is no high pressure involved, so there is little difference between them as far as AFPR goes. Any 255 will require one.

Of course some people say "my car is fine with the stock reg and 255," but that just tells me they dont have a logger, dont know what they are looking at, or dont care about getting the car to right as intended in closed loop. Which is fine. Just beware

Its all a matter of how you define "need."

I personally would do the FPR upgrade for a 255, but let it slide on the 190.

Think of the high base pressure you get from a sotck reg and a 255 as boost creep on your turbo. You can rightly call it fuel pressure creep. I used to get boost creep to 18 psi on my 14b. The car ran well with 18 psi, so was anything wrong with that? You could say no, because it ran fine, or you could say yes, because I had limited control over boost, and the WG wasnt doing its job. Same thing with fuel pressure creep. The issue is that more often than not, the fuel pressure creeps enough that your fuel trims are completely bolixed and closed loop runs like shit, and economy goes down the shitter. If you are tuning logger/afc style, you will jsut adjust your low trims to try to make up for it. If you are running [some kind of datalogger], the problem is so obvious, it'll drive you nuts. Trust me

So again, it all depends on how you look at it, and what your goals and concerns are. For a low HP daily driver I dont think its worth running around with banjaxed trims 99% of the time. For a track car that spends most of its life at WOT, who cares. For street cars I personaly suggest using a FPR for the 255, or if thats not in the budget, and you are sure you arent going to go over say 120-125 mpg traps, just go with the 190 and drive it on. I've seen it do 124 mph, very capable pump. And the fuel pressure creep is minimal.

Running a large pup and stock reg has nothing to do with WOT performance. (IMG:style_emoticons/default/smile.gif) Its about closed loop operation, which you dont care about on a race car but probably do on a daily driver. (IMG:style_emoticons/default/wink.gif)
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So you might not have an *apparent* issue, or you might not have any issue at all... or you might have an issue you aren't as easily able to observe, other than gas mileage, power, etc... although if you boost, this could become something of an issue. An AFC and some tuning can sort this out, but it's cheaper and easier to run an aftermarket FPR and be done with it.

k...I'm confused by why the wiring for this is causing so many questions.

All I did was mount mine in my cage, wire the red wire to the existing red wire, the black to the black and shrink wrap them...

Right, but the S12 ECU varies voltage based on conditions, and a variable voltage system might burn out the pump. Even if it doesn't burn the pump up, you are STILL flowing extra current thru the system... WHICH has been known to heat the wires up, AND ALL that extra current is flowing thru the ECU! It might be fine... it might not. If the ECU was engineered to handle the stock pump's 2amp draw, you double that or whatever the additional current draw of the Walbro is, you might burn the driver out of the ECU. Maybe it will be just fine, but hell, for the cost of a relay and a bit of simple wiring I'd rather do it safe....

I will write a how-to for both stock-motored S12 fuel pump upgrade and S13-powered fuel pump upgrade, that should iron things out.