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Direct power feed from battery to fuel pump

+7
weblizzer
Digitalfaze
GTI-R US
nomad
pulsarmoley
Wocka
Gaz GTiR
11 posters

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Gaz GTiR

Gaz GTiR

Direct power feed from battery to fuel pump Icon1 22-06-2010, 16:57

To increase voltage too and re earth the fuel pump.

Basically it involves running a power feed direct to the fuel pump via a 12v switching relay to increase the voltage available to the pump and at the same time improve the fuel pumps earthing points.......

It is best done if you have upgraded your fuel pump (Walbro or equivalent) and having fitted your battery in the boot to make life a little easier.

Solder all cable joints and insulate the joints well.

Run a length of 30 amp cable from the battery to a 12v switching relay (with pins 85,86 ,87,30) which can be located next to the fuel pump cover. It would also pay to fit a fuse in this power line no more than 12 inches from the battery.
Connect this power cable to pin 87 of the relay. This is the new power feed for the pump, not the relay switching feed.
Cut the stock live feed at the fuel pump plug leaving an inch or so of cable, strip this cable back and solder one end of a another length of 30 amp cable to the cable at the plug end solder the other end of this to pin 30.
Solder the other end of the cable you've just cut (the OE pump power feed) to relay pin 86 (this is the switch power feed for the relay).
Solder a short length of the 30 amp cable to pin 85 and earth this as close as possible. I think I cut the original earth feed from the pump plug and soldered it here too, then soldered a 30 amp earth cable to the fuel pump plug and earthed that to the same place as the relay.

You need to keep the original fuel pump relay in as, you're still using that feed, to switch the new relay on and off.
It should be noted that you won't get any voltage on the pump side of the relay, unless the fuel pump is priming (the 2 or 3 seconds after you turn the ignition on) or the engine is running. That may sound strange but, the fuel pump only needs to operate at these times so, that's how it works.

So, if you're trying to measure a voltage on the fuel pump side of the relay, without the ecu priming the pump or the engine running, you won't get a reading.

Wocka

Wocka

this worth doing gaz? (im running walbro and battery is in boot)

pulsarmoley

pulsarmoley
moderator
moderator

What sort of power and spec you running?

Wocka

Wocka

wow fast reply! erm 1.2 bar on standard turbs, yet to be dyno'd

front mount
3" elbow and front exit
mines ecu
apexi filter reloctaed behind light
etc etc

pulsarmoley

pulsarmoley
moderator
moderator

I think its only recommended if your pushing close to the limit of the standard injectors etc or if you were gonna go for high power? Hopefully someone else will confirm it but as your battery is already in the boot I'd say it would be a good idea as its a simple mod. I would think your injectors would be close to Max running 1.2bar. At a guess I think you would be seeing around the 320hp figure.

Wocka

Wocka

injector wise i have a adj afr set at 4 bar, as you said as its all there i may aswel do it, i just need a soldering iron :/

Gaz GTiR

Gaz GTiR

Not realy anything to do with that moley. More of a case of the standard loom being old & not pushing enough current threw to fuel pump so the engine would not be getting enough fuel on boost or top end of rev range.

So best to be safe than sorry Smile

Yes wocka well worth doing for piece of mind Smile

pulsarmoley

pulsarmoley
moderator
moderator

Ah yes forgot that part Embarassed 

Wocka

Wocka

cheers guys, will get on with doing this soon Smile

nomad

nomad
Admin
Admin

I thought it was 3bar for fuel? As said already its mainly to get a good feed to the pump bypassing the old wiring . And doesnt the standard injectors max out at something like 1.4 ????

pulsarmoley

pulsarmoley
moderator
moderator

Standard pressure is 3bar but with the adjustable fpr he's got it at 4 which I presume is ok as it won't go any higher than 5.2. Some do say that its not worth upping the fuel pressure? But I guess as its not a mappable ECU the fpr could be adjusted to get the fuel mixture right on the rollers?

GTI-R US

GTI-R US
Management
Management

yep basically its a cheat with undersize injectors by upping the fuel pressure. its not the best way to do it (far better to run correct size injectors) but it will suffice

http://www.gti-r-us.co.uk www.force500.com

Digitalfaze

Digitalfaze
web admin
web admin

Gaz GTiR wrote:Not realy anything to do with that moley. More of a case of the standard loom being old & not pushing enough current threw to fuel pump so the engine would not be getting enough fuel on boost or top end of rev range.

So best to be safe than sorry Smile

Yes wocka well worth doing for piece of mind Smile

Was told this should be done when i go to get my pump fitted and fueling checked for those exact reasons

http://www.avaloncreative.co.uk

Wocka

Wocka

Doing this over the nxt few days. Has anyone done this yet? Any pics of what should be cut etc, took the cover off earlier and saw there was 3 plugs and dont want to cut something i shouldnt!

Gaz GTiR

Gaz GTiR

My mate who is good with wiring did mine so not realy got any advise apart from the how to guide above mate

nomad

nomad
Admin
Admin

Maybe a couple of pics of where its cut in on what plug would be helpful gaz Wink 

Gaz GTiR

Gaz GTiR

I will get some tomoz & post them up Smile

nomad

nomad
Admin
Admin

Sure it will help a few out mate ... so nice one cheers 

Wocka

Wocka

Yeah just a piccy of the plug would be all i need i think Very Happy

weblizzer



anyone had pics on this? planning to rewire my pump to have extra pressure?

21Direct power feed from battery to fuel pump Empty Re: Direct power feed from battery to fuel pump 28th February 2014, 10:35 pm

Rot box revival!



Instead of using the original pump wiring, what if you just ran an ignition feed to the relay switching side? Would this do away with the fuel cut? I know it would be running all the time the ignition was on but just wandering?

grim_d

grim_d

Here is a diagram and some photos courtesy of olliecast and gtirx2 from the oc, I don't think they will mind, don't even think they are active members anymore.

The diagram shows a cut off switch, this isn't needed unless you are competing and have regulations to adhere to but might not be a bad idea. Also this is a twin pump set up, for single pump you just do away with one of the relays.

And for anyone else as stupid as me, the new relay you install has pins 85,86 ,87,30, I didn't understand this at first.

For everything required to do this came in at about £40 but that is with battery already in the boot.

Direct power feed from battery to fuel pump Swirl

Direct power feed from battery to fuel pump P1010886

Direct power feed from battery to fuel pump P1010913

nomad

nomad
Admin
Admin

Nice one mate cheers for posting it up  thumbsup 

grim_d

grim_d

Here is some more info.

Common pump amperage draw chart.
Direct power feed from battery to fuel pump Fuelpumpameragechart1

Wire selection chart based on current and run length. (For reference I am using 12AWG for the mod on a Bosch 040)
Direct power feed from battery to fuel pump Wiringdiagram

Source: http://www.evoxforums.com/forums/showthread.php?t=52658

simigeri

simigeri

Pics needed from the fuel pump connector top of the fuel tank!
Whicj cable is the ground, power ect, and which connector is the level sensor?

Thanks

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