Fuel pump relay

[Bobby^]

After finally deciding on a fuel pump i opted for the walbro 255. When i went to get it installed (im too ***** to do it myself) they told me after they installed it they will check the current and may need to install a seperate relay from the battery.

Ive heard that you need to do this with some of the bosch pumps, but is this really necessary, im only going to be running (hopefully) 190~rwkws.

Should i just have them install it, then chuck it on the dyno and if the ratios are fine, not worry? or should i jsut trust them ?

I just dont want to be ripped off.

[dnb]

they are being honest mate, thats all you can ask from a shop.

personally id install the relay. its only a 1/2 hour job

[StockyMcStock]

the more voltage that gets to the pump the more it will pump! have seen reports on a VL turbo fuel pump which gave 30% more flow @ same rail pressure when it was given +14V instead of +11 like it usually sees in a VL. the thicker guage wire going to it generally the more voltage it should see, installing a separate relay is probably easier than rewiring the original one.

[predator]

Like they say, more voltage = better...

however the last two pumps (one walbro, one bosch) I have installed I have had no troubles with the stock wiring at levels below 200rwkw.

I guess if I was pushing the power past that, it would be something to consider. You can always stick a multimeter on it on the dyno at full chat, see what is happening.

[Bobby^]

Ok, i think ill get the relay done, but im definatly going to shop around for prices.

Thank you guys, much appreciated.

[Sydneykid]

You need to be careful when selecting Walbro pumps. As you can see from the attached, the GSS341 is rated at 255 lph, that's at zero boost and at 13.5 volts. If you install one in tank with the standard Skyline wiring it will run at 12 volts, that's 215 lph. Then add some boost, say 20 psi (1.35 bar) and they are down to 180 lph.

[yogi000]

which is a better pump?? i need to get a new one but unsure on which one.

I want to try one of these to fix a problem i'm having with detonation......it will not detonate on the dyno but on the street it will randomly detonate. So i was gonna try one of these two pumps.....i currently have a r33 gtr pump installed.....running on the standard r32 gtst wiring. Any ideas would be appreciated.

Should i try a constant power from the battery???

1. bosch 040 intank.....supposedly doesnt need a sock????

2. Walbro 255l intank pump

thanks

[R32-GTS]

I checked my fuel pump voltage in my gtr the other day and it was only getting 10.4 volts from the factory wiring. So i ran 8 guage wire from the battery to the boot using the sotck wiring to switch a relay now it has 13.7 volts.

[yogi000]

that sounds like an idea i might try, what kind of relay did you use and where did you get it....i'm abit confused on what type to use, and then basically ground the relay......draw power from the battery and the ignition wire from the orginal wiring??? is that somewhere in the ballpark on what needs to be done?

[R32-GTS]

yeh just a general bosch automotive relay. i think i used a 30amp one.

[Sarumatix]

Has anyone gone into more detail about rewiring the fuel pump?

[boostn32]

just use the factory fuel pump power wire as the switching power to the relay, and run a new power wire to the relay from the battery,

make sure it will carry the correct voltage over the lenght of the wire, the longer it is the more voltage drop due to resistance,

the size power cable will depend on how much power the pump will draw so get a nice thick one at lease 2.9mm2 core.

earth the relay to body and run power out of relay to pump. The relay packet will show the correct way to wire it up on the terminals.

30AMP relay will do for 1 pump.

Edited November 28, 2009 by boostn32

[R31Nismoid]

Has anyone gone into more detail about rewiring the fuel pump?

Read the FI Guide - fully detailed link contained within.