fuel pump direct battery power

[jeremy242]

I have been advised that i should wire my fuel pump dirctly to the battery to reduce voltage drop. Can i just use the existing power source for the pump to trigger the relay and power the pump? Is it really that easy? Obviously i still have to wire up the rest of the relay but is that it? Thanks

[R33E8]

Yes. it's really that easy..

[Rabboni]

If voltage drop through a relay was that much of a concern then they wouldnt be used at the factory. Dont wire it directly to battery power,just use the existing setup.

[jeremy242]

I already have the battery in the back as it is, i would be using the factory fuel pump wiring as the trigger for the new relay to directly connect the pump to a good 12v source

[jeremy242]

i was more concerned with the 21 year old wiring that it was having to travel through rather than the factory set up

[roboticnissan]

Use the existing relay.

[nieko]

I actually JUST did this. haha

Boost It Up - AP Boss Fuel Pump - Turbo Magazine (http://www.turbomagazine.com/tech/0804_turp_fuel_system_harness/ap_boss_fuel_pump.html)

starting the car up tomorrow lol

[garagelu]

http://www.painlessperformance.com/Manuals/50102.pdf

Here's the kit I'm installing this week. I've been having fuel pressure drop after 6K rpm. I've narrowed it down to voltage drop so hopefully this fixes it.

[Rabboni]

I dont know... Im personally not a fan of running more wiring around my car that isnt absolutely necessary. Plus, if your having voltage drop problems with the factory wiring wouldnt it make sense to just fix the existing wiring, rather than to have bad wiring control a new relay?

[nieko]

Do you really want to go thru the whole car tracing the fuel pump power wire just to replace it?? when you could just run a new one and tuck it nicely or something?

And the old wiring still works, just doesnt hold the strong 12v at all times.

The old wiring is only clicking the relay on, should do the job just fine.

[NiSilS14]

you could do this, but it requires a little more cash.
Kenne Bell Boost-A-Pump (http://www.kennebell.net/accessories/boostapump/boostapump.htm)

[jspaeth]

I dont know... Im personally not a fan of running more wiring around my car that isnt absolutely necessary. Plus, if your having voltage drop problems with the factory wiring wouldnt it make sense to just fix the existing wiring, rather than to have bad wiring control a new relay?

Pretty much anyone who actually cares about their car and wants RELIABLE fuel delivery rewires the fuel pump directly to the battery.

IIRC, the factory setup has the fuel pump in a circuit with other things, and as the load on the car changes etc etc you can more easily get inconsistent voltage.


I measured the fuel pump voltage under my "OEM" wiring setup and I see about 12.5 volts.


However, the alternator puts out close to 14V when the car is running, so you should be able to utilize that advantage by wiring directly to the battery and getting 13.5-14.0 V to the pump.

[Martino]

Pretty much anyone who actually cares about their car and wants RELIABLE fuel delivery rewires the fuel pump directly to the battery.

IIRC, the factory setup has the fuel pump in a circuit with other things, and as the load on the car changes etc etc you can more easily get inconsistent voltage.


I measured the fuel pump voltage under my "OEM" wiring setup and I see about 12.5 volts.


However, the alternator puts out close to 14V when the car is running, so you should be able to utilize that advantage by wiring directly to the battery and getting 13.5-14.0 V to the pump.


Could you essentially just find the power wire off the sending unit, cut and splice into a power source on ignition?

Or does it need to go through the relay? Where's that specific relay?

[jspaeth]

Could you essentially just find the power wire off the sending unit, cut and splice into a power source on ignition?

Or does it need to go through the relay? Where's that specific relay?


The easiest way to do it is to use the OEM power wire running to the fuel pump as a TRIGGER on the coil side of a NEW, second relay.

Then, run the power to that relay DIRECTLY from the battery (if it's in the trunk that is cake).

This way you get the maximum voltage possible to the battery

[Chrisq0904]

Im having issues with my fuel pump and I wanna directly wire it to the batt and after reading this I understand what I have to do. But I do not understand what wires go to where. If someone could post a write-up or pm me a step by step process on what wires go where that would be great. Thanks in advance, sorry if this is a "noob" post..

[jeremy242]

Thanks for the input

[Martino]

The easiest way to do it is to use the OEM power wire running to the fuel pump as a TRIGGER on the coil side of a NEW, second relay.

Then, run the power to that relay DIRECTLY from the battery (if it's in the trunk that is cake).

This way you get the maximum voltage possible to the battery


I'm looking to do this exactly, especially because my battery is in the trunk.
My only issue is...I'm medicore at wiring and every diagram I've looked at confuses the fuck out of me LOL

Any godly chance you could ghetto rig me a diagram? haha.

<3 love you long time.

[Chrisq0904]

Terminal 86 - Ground
Terminal 30 - Direct to battery with inline 30A fuse
Terminal 85 - B/Y wire from pump (trigger)
Terminal 87 - Other end of B/Y wire (trigger)

I think this is correct just unsure if i have the trigger wire correct.

[240Zfunahollic]

Deatschwerks sells everything you need for like $20.

[jspaeth]

I'm looking to do this exactly, especially because my battery is in the trunk.
My only issue is...I'm medicore at wiring and every diagram I've looked at confuses the fuck out of me LOL

Any godly chance you could ghetto rig me a diagram? haha.

<3 love you long time.


Okay get a NEW relay that can support the current (not sure how much).


You cut the power and ground wires going to the pump.

Run a new, thicker ground from the pump to chassis.


Take the OLD pump power wire, and run it to the + side of the coil on the relay. Run another wire from the ground side of the coil to the chassis.


Run a wire from the battery to the switched side of the relay, and then another wire from the other switched side of the relay to the + terminal of the pump.


IIRC, the current dircetion through the relay doesn't matter (wait for someone else to confirm this)

[Rabboni]

Pretty much anyone who actually cares about their car and wants RELIABLE fuel delivery rewires the fuel pump directly to the battery.

IIRC, the factory setup has the fuel pump in a circuit with other things, and as the load on the car changes etc etc you can more easily get inconsistent voltage.


I measured the fuel pump voltage under my "OEM" wiring setup and I see about 12.5 volts.


However, the alternator puts out close to 14V when the car is running, so you should be able to utilize that advantage by wiring directly to the battery and getting 13.5-14.0 V to the pump.

I still havnt done this, and i have never had any fuel delivery problems. Im probably not making nearly as much power as you though, so I see where you are coming from.

Continuing: http://4x4icon.com/offroad/headlight_warning/relay_diagram.gif

85: this is where you would wire the power wire of your existing fuel pump wiring as the trigger.
86: this you would wire to a reliable chassis ground.
30: Wire your power wire from the battery here.
87: Run the power wire to your pump from here.

[slider2828]

Deatschwerks sells everything you need for like $20.

Thanks MAN!!! I just ordered this.... I didn't know a kit existed....

Plug and play is the best and it was $30 + 13 shipping....

Great thread, never checked for voltage drop, but since I do a lot of trackdayz I should have thought about this....

Great thread!

[Martino]

Okay get a NEW relay that can support the current (not sure how much).


You cut the power and ground wires going to the pump.

Run a new, thicker ground from the pump to chassis.


Take the OLD pump power wire, and run it to the + side of the coil on the relay. Run another wire from the ground side of the coil to the chassis.


Run a wire from the battery to the switched side of the relay, and then another wire from the other switched side of the relay to the + terminal of the pump.


IIRC, the current dircetion through the relay doesn't matter (wait for someone else to confirm this)

According to the Deatschwerks kit it includes a 30am relay so I'm assuming that would suffice?

And I just read that over again...
Still confused...I tried drawing a diagram of what you explained but I'm doing something wrong.

Ugh.

[lok]

http://www.auto-nomics.com/images/fuelpump_relay_wiring.gif

this might help.

[xiaphin]

Deatschwerks Fuel Pump Hard Wire Kit - $29 (http://www.deatschwerks.com/catalog/product_info.php?cPath=0_24_40&products_id=231)

[slider2828]

30AMP is more than enough....

[jeremy242]

awesome diagram, it doesn't get any clearer then that.

[Martino]

So good.
I <3 you.

[Bigsyke]

Pretty much anyone who actually cares about their car and wants RELIABLE fuel delivery rewires the fuel pump directly to the battery.


by wiring directly to the battery and getting 13.5-14.0 V to the pump.


I sure hope not.

This mod has left me stranded before. Bosch 40amp relay crapped out on me pretty fast.

[codyace]

I sure hope not.

This mod has left me stranded before. Bosch 40amp relay crapped out on me pretty fast.

That's a very rare occurance to be honest, only time I've ever had issues with relays failing (other than the random OE ones dying at the shop) are when I had some installed upside down (connector up) and rain water getting in them on a little off road buggy i had.

[slider2828]

Ok I just finished this... some people just never bothered to put up the diagram so here we go... I also left my stock fuel pump fuse and fuel pump relay....

On my kit from DW... I made all my modifications on the chassis plug NOT the pump side of the plug coming from the fuel pump cover..

Red = Battery +
White = Battery -
Yellow = Red with Black Strip on the plug side
Black = Switched 12V Red with Black Strip on the Chassis lead we cut

Finally cut the black wire cause I liked chassis ground, so I cut the black wire and on the plug side I grounded it to a good chassis ground...

Rest of the wires (green and one other color I don't remember, don't touch)...

Also I have another fuse between the relay and the battery 12V...

Hope this helps....

[garagelu]

Ok I just finished this... some people just never bothered to put up the diagram so here we go... I also left my stock fuel pump fuse and fuel pump relay....

On my kit from DW... I made all my modifications on the chassis plug NOT the pump side of the plug coming from the fuel pump cover..

Red = Battery +
White = Battery -
Yellow = Red with Black Strip on the plug side
Black = Switched 12V Red with Black Strip on the Chassis lead we cut

Finally cut the black wire cause I liked chassis ground, so I cut the black wire and on the plug side I grounded it to a good chassis ground...

Rest of the wires (green and one other color I don't remember, don't touch)...

Also I have another fuse between the relay and the battery 12V...

Hope this helps....

The way you wired it makes the pump stay on all the time when the key is turned in the on position. If it does this, that's not the correct way to do it since if you somehow crash and a fire starts, the pump is going to keep pumping fuel.

[SuperiorS14]

yea your supose to pull the power supply from the ign. 12v and u should also use a relay.

[slider2828]

The way you wired it makes the pump stay on all the time when the key is turned in the on position. If it does this, that's not the correct way to do it since if you somehow crash and a fire starts, the pump is going to keep pumping fuel.

anyone got a diagram on how to do this? I looked through the FSM, it does really give me any idea on this trunk plug.


A relay is basically like a switch correct? If the 12V is on, then the relay passes eletricity through I know that much. So on the switch 12V, it acts as a trigger? So 1 click it turns on the relay, and 1 click again and it turns off the relay?

[slider2828]

I also have 2 relays which I think will be fine... Key goes to the egi fuel pump relay that 12v goes to my relay.... So there are 2 relays... If the original shuts off like designed, this one will do so as well.... right?