How To Direct battery power to fuel pump

S

SIR GTIR

Member
awesome tread Lads JUST What i've been looking for

I'm currantly running a walbro 255lp
GT3071R @ 18psi
Sard 800cc injectors etc etc

but as i've read in Here http://forum.gtiroz.net/viewtopic.php?f=14&t=438&start=240
the walbros generally run out at 17psi
So after emailing Ed i tryed to set up the direct feed
as posted above found the Black and red to be the trick
My batterys still up front so i've run the cable from the battery round the front to the relay enclosure and was going to loop a wire to the new relay But..

Can i ground the other terminal ?? on the other side of the coil??
thanks for reading
Paul
 
S

SIR GTIR

Member
hey Cheers Mate that would be Coool in the shed as i type well turns out the relays nackered so theres most of my problem right there would still like to see your pic tho mate to confirm i've got it right velly4 thanks very much

Paul
 
V

velly4

Member
The 2 wire plug is to the pump. Black wire with the reddish/purple stripe is the active. The black with the odd grey spot is the earth.

 
S

SIR GTIR

Member
thanks buddy colours change at the other end looks like i did it the hard way as always i've wired mine at the front Explains my trouble aye

Paul
 
S

SIR GTIR

Member
at the fuel pump relay i've run the feed round to the relay enclosure and then sent it down the back to the pump
but yeah seems it'll be another week maybe after i get another relay since the 70Amp one i got to be safe died before even getting used =(

I'll post up pictures once i've got it in a working state =)
 
S

SIR GTIR

Member
Right got it all functioning today

So taped into the active fuel pump feed from the std relay (black/ red stripe)
taking that to trigger the new relay then earthed the other side of the coil
http://sirgtir.orconhosting.net.nz/other installs/fuel relay mod.jpg

i run the cable down the loom in the inner guard i also run a loop of wire with a switch to isolate the new relay (sometimes floods at start up)

then at the back

first i cut the std fuel pump feed (black/ red stripe)
soldier the New feed to the wire before the plug (as above)
the std feed i bent back on itself and insulated the end

then i pulled the insulation back and cut the insulation back to the ground wire of the Pump (black/ grey spot)
and placed a crimp terminal on to earth back to the body
http://sirgtir.orconhosting.net.nz/other installs/new pump feed and re-earthed.jpg

my idle voltage at the pump went from 11.6 volts to (13.6 with the std earth) to 13.9 with the New direct feed
 
wrc

wrc

Member
I did this mod yesterday, all went very well.

However the car how feels very sluggish... Underpowered to compared to what it was before. Voltage at the pump is now excellent - however I think i may now be overfuelling possibly where the original FPR is weak.

Anyone had any experience of this?
 
G

geoff pine

Well-Known Member
wrc said:
I did this mod yesterday, all went very well.

However the car how feels very sluggish... Underpowered to compared to what it was before. Voltage at the pump is now excellent - however I think i may now be overfuelling possibly where the original FPR is weak.

Anyone had any experience of this?
Click to expand...
When mine was over fuelling re grounding the maf solved it :thumbsup:
 
pulsarmoley

pulsarmoley

Member
Ok so ive read this thread and can understand the theory of doing this mod as i deal with basic circuits in my job but, if the fuel pump is fed from a relay in the engine bay, why is this relay not supplying the higher voltage(13.5V+) as standard? The earth i get as they can build up a resistance over time from age etc. Could someone explain what i have overlooked/not understood as i may consider doing this at some point, thanks.
 
S

SIR GTIR

Member
take the 20year old wiring and the Gauge of the cables enough reason thats why i measured it with a meter i didnt believe it myself
 
stevepudney

stevepudney

GTiROC CHAIRMAN
Staff member
wrc said:
I did this mod yesterday, all went very well.

However the car how feels very sluggish... Underpowered to compared to what it was before. Voltage at the pump is now excellent - however I think i may now be overfuelling possibly where the original FPR is weak.

Anyone had any experience of this?
Click to expand...
I assume you've already moved the battery to the boot ? What battery type did you move to the boot, was it the small standard (same as micra) one or has it been upgraded to a larger one with more output ?

If you do this mod to a car that has a mapped ECU (standalone ecu or Nistune etc.) you should take into consideration what Ed says earlier in the thread:

Fusion Ed said:
I don't specifically mean earth. The drop is more likely to be on the live side, as that run is longer on the pulsar. Under boost I have had fuel pumps on pulsar drop to 8volts. This causes a pressure drop. this can be hidden if the injectors are large as you just open the duty further but this means the map is not linear - and is how I can tell if there is a problem with the fuel pressure. I.e. x load = x fuel, 2x load = 3x fuel = problem. x load = x fuel, 2x load = 2x fuel = expected, all is ok.
Click to expand...
If your car does have a specific map that suited a specific mechanical set-up, by doing this mod you will have almost definitely altered your fuel map.
 
stevepudney

stevepudney

GTiROC CHAIRMAN
Staff member
pulsarmoley said:
Ok so ive read this thread and can understand the theory of doing this mod as i deal with basic circuits in my job but, if the fuel pump is fed from a relay in the engine bay, why is this relay not supplying the higher voltage(13.5V+) as standard? The earth i get as they can build up a resistance over time from age etc. Could someone explain what i have overlooked/not understood as i may consider doing this at some point, thanks.
Click to expand...
Once upon a time this forums flavour was a little more technical than it appears to be now, this and many other technical subjects like it were discussed time and time again, so although it is frustrating searching and filtering through all the old threads you will eventually find all the answers and more to your questions are buried in the OC archives.
A few key reasons for this mod being so important if your turning the power up on your pulsar are explained by Midnight purple and Ed in the first part of this thread. It's not really a power mod it's more of a reliability mod replacing a weak link in the strong chain your attempting to build. Basically though if modifying for more power you will want a stronger more reliable fuel supply to your "bigger" injectors, replacing the standard 20 year old fuel pump for a more powerful (Walbro, Bosch etc.) is a must, then as mentioned above take into account the cars "20 year old wiring" which was designed to run what is essentially a glorified shopping trolley, combine that with the numerous earth problems the pulsar is tortured by and you have the basis of the reasoning supporting the mod. This thread http://www.gtiroc.com/forums/showthread.php?37739-Battery-Box&highlight=battery also makes good reading if you've not already moved the battery to the boot.

Hope that helps

Steve
 
pulsarmoley

pulsarmoley

Member
stevepudney said:
Once upon a time this forums flavour was a little more technical than it appears to be now, this and many other technical subjects like it were discussed time and time again, so although it is frustrating searching and filtering through all the old threads you will eventually find all the answers and more to your questions are buried in the OC archives.
A few key reasons for this mod being so important if your turning the power up on your pulsar are explained by Midnight purple and Ed in the first part of this thread. It's not really a power mod it's more of a reliability mod replacing a weak link in the strong chain your attempting to build. Basically though if modifying for more power you will want a stronger more reliable fuel supply to your "bigger" injectors, replacing the standard 20 year old fuel pump for a more powerful (Walbro, Bosch etc.) is a must, then as mentioned above take into account the cars "20 year old wiring" which was designed to run what is essentially a glorified shopping trolley, combine that with the numerous earth problems the pulsar is tortured by and you have the basis of the reasoning supporting the mod. This thread http://www.gtiroc.com/forums/showthread.php?37739-Battery-Box&highlight=battery also makes good reading if you've not already moved the battery to the boot.

Hope that helps

Steve
Click to expand...
Ok thanks, will have a look at that thread, Pete.
 
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