quick 12V fuel pump mod question w/ diagram

[2_fast_240]

http://i221.photobucket.com/albums/dd16/catabor/fuelpumpwiring.jpg

So, I want to do this today, but want to make sure I do it right.

Im just a little confused on the wiring for pin 85 (trigger) and pin 87 (12V to pump)

Should I wire it the red, blue, or green way? Im hoping blue is acceptable so I wont have to pull the pump out. And if I can do it the blue way, should I cut the section marked "A" in the diagram? Or is there a different, better way to do this?

All help is greatly appriciated.

[lok]

nm to early and didnt notice your relay drawing

[lok]

Here we go

http://images.turbomagazine.com/tech/turp_0804_25_z+fuel_harness_system+fuel_pump_schem atic.jpg

[g6civcx]

Before I tell you how to do it, what fuel pump is this, and what car is this for?

[2_fast_240]

Its a walbro 255. 91 240sx se ka24det. non-cali. ecu if that matters.

Where in VA are you from? Just curious.

[g6civcx]

Its a walbro 255. 91 240sx se ka24det. non-cali. ecu if that matters.

Actually, it does matter. The ECU controls the fuel pump so it's not good to run the pump always constant on.

Why are you rewiring it? Read my other threads to find how relays work. 87 goes to pump power and use switched power to trigger one of the 85/86 pins. The other of the 85/86 pair goes to ground.

Where in VA are you from? Just curious.

Alexandria. Hop over to midatlantic240sx if you haven't already.

[fbiphil]

I've wired up a few KA swaps into Datsuns and have always run the pump off an ignition source rather than through the ECU.
Although I've never had a problem running them this way, I am curious- what would the ECU control on a system like this? I understand that on newer, returnless systems it could limit voltage to the pump or some such thing, but what would be the difference on a KA?
Just wanted to know- not trying to argue!

[2_fast_240]

Actually, it does matter. The ECU controls the fuel pump so it's not good to run the pump always constant on.

Why are you rewiring it? Read my other threads to find how relays work. 87 goes to pump power and use switched power to trigger one of the 85/86 pins. The other of the 85/86 pair goes to ground.



Alexandria. Hop over to midatlantic240sx if you haven't already.

Im rewiring it because im experiencing a lean issue in boost as well as erratic afrs when cruising. People have traced similar issues to the voltage at the fuel pump. http://www.ka-t.org/walbrorewire.php. This ensures 12v+ to the fuel pump at all times the ignition is turned on.

Yes, I understand how relays work. Thats what will keep the pump from being constantly on. I know 87 goes to pump power, and I know 85/86 is the trigger and ground.

My question is, where should I get the trigger from. It seems as though I could just get the trigger from the original + fuel pump wire. But im not sure if it would be ok to wire the 87 wire to the original wire too.

But, pictures are worth a thousand words. Thats why I drew the diagram. 3 different colors for 3 different possible wiring schemes. I wanna know which is best, or if all will work, etc.

Not trying to be a dick, but has anyone actually looked at my diagram and tried to understand what im asking. I know its sloppy, but its plenty legible. If yall cant make out the diagram, lmk and ill make a better one.

Thanks for the link to midatlantic240sx! Ill probably do that next chance I get.

[2_fast_240]

I've wired up a few KA swaps into Datsuns and have always run the pump off an ignition source rather than through the ECU.
Although I've never had a problem running them this way, I am curious- what would the ECU control on a system like this? I understand that on newer, returnless systems it could limit voltage to the pump or some such thing, but what would be the difference on a KA?
Just wanted to know- not trying to argue!

Thats kinda what im wondering. The diagram I drew will keep constant 12v+ to the pump any one of the 3 ways I drew up.

Thats why im thinking the power to pump, from relay, should probably just "T" into the original pump power wire. That way it still gets any info it MIGHT need from the ecu. Not sure if that would overload something though since im not so good with electronics. Also not sure if I can "T" into the original wire for the trigger, if thats where im sending power.

Its all in my head, I just have trouble putting it into words, lol. Hence....the diagram, lol.

[g6civcx]

I understand what you want to do now. It's not that difficult.

Read my post here: http://www.zilvia.net/f/showpost.php?p=2025683&postcount=2

The black/yellow pump power goes to pin 87. Use any switched source and tap to one of pin 85/86. Route the other one of 85/86 to ground.

Your picture is kinda confusing, but you need to divert the black/yellow power away from the stock relay and add in your on relay. Make sure you remove the stock relay or at least tape off the open wire.

The easiest way to run power to trigger the relay is to use a switch. battery(+) - switch - pin 85 or 86.


That way, you can hide the switch somewhere as a theft deterrent.


If it's unclear let me know. I'll make a diagram for you.

[cotbu]

I've had great success using the stock relay 12v wires as a trigger. If you're wiring in a new relay because you old wiring is shot this may not work for you.
http://i18.photobucket.com/albums/b142/COTBU/relaytrigger.gif
You only really need one fuse there but....
http://i18.photobucket.com/albums/b142/COTBU/fuelpumprelaysocket2.jpg

[2_fast_240]

Thanks for all the help guys! I think I got it now. And now you really got me thinking on that switch idea. Good call on that!

[iHeartTheTouge]

sorry i need to bump this. i'm doing this right now. just finished wiring it up but the pump still isnt turning on. i have it as

30 - 10a fuse - batt.
85 - grounded
86 - switch - grounded
87 - directly to pump.

i read the thread but i'm a little frustrated right now and not really making much sense of anything. i'm afraid i've fried the fuel pump. i dont want to have to order fuel pump #4.

edit: i'm using a 5 pin relay and read that you can leave pin 87a unplugged and it will act as a 4 pin relay. not sure if thats correct anymore. i left my 87a unplugged. i'm seeing no power past the relay.

[wangan_cruiser]

check for grounding. i just fixed this issue last night and turns out to be grounding issue.