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No Power To Fuel Pump

Crans

By Crans,
in Engines & Forced Induction

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Crans Mentor

Crans

Posted
Posted

Just tried hooking up a relay to my fuel pump to feed direct battery voltage to it and seams to be an epic failure

I was using a 12v 40amp normal open relay. It was wired up correctly

Blue trigger wire going into switch pin then battery to fuel pump on the switching side.

I measured voltage coming from the ecu and its nothing

Undid all changes and fuel pump still wont turn on.

Any one know what fuses i need to be checking?? I can find any blown ones.

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KiwiRS4T Grand Master

KiwiRS4T

Posted
Posted

If you have the number Nissan can cut a new one from the code. Some locksmiths may be able to I don't know but the average key bar probably can't - they will need one to copy - should be possible if you can get the broken bit out.

Torques Mentor

Torques

Posted
Posted (edited)

The fuel pump fuse in in the back of the car (where the other fuses are)

It is labeled in English!

(I think 15A - blue)

Also, depending on how you hooked up your relay, you might have damaged your fuel pump controller.

(Just a thought)

Also I really don't know why people do this mod, since the fuel pump controller jumps to full voltage once

the car moves :)

There is no resistor which cripples the pump .. the FPC actually has logic and a number of components in it.

Hope this helps ..

fpcontmod2.jpg

Edited by Torques
Hanaldo Grand Master

Hanaldo

Posted
Posted

Also I really don't know why people do this mod, since the fuel pump controller jumps to full voltage once

the car moves :)

There is no resistor which cripples the pump .. the FPC actually has logic and a number of components in it.

Well voltage is only one part of it, you need the wiring to be able to handle a higher amperage as well. Secondly, lots of people have problems with surging at idle and low rpm because aftermarket fuel pumps are designed to be run at alternator current.

Torques Mentor

Torques

Posted
Posted

Hello ..

I recently installed a Tomei, and it hums along just fine.

But higher load as in 'wattage' could be an issue if your overstress the pump controller.

Still there are people out there who do the 'fuel-pump-mod' with the standard pump installed.

I find this useless ..

Well voltage is only one part of it, you need the wiring to be able to handle a higher amperage as well. Secondly, lots of people have problems with surging at idle and low rpm because aftermarket fuel pumps are designed to be run at alternator current.

Hanaldo Grand Master

Hanaldo

Posted
Posted

Still there are people out there who do the 'fuel-pump-mod' with the standard pump installed.

I find this useless ..

Oh right. Yeh I see so little reason for this that I didn't even consider that there were people doing it... lol.

MrStabby Grand Master

MrStabby

Posted
Posted

Also I really don't know why people do this mod, since the fuel pump controller jumps to full voltage once

the car moves :)

Once that box fails, the direct wire is a good option :) I've had two die.... but agree that for many people its pointless. They just get scared when they see the lower voltage across the pump when the soft earth is switched in because they measure at idle or ign.

OP - the earth is switched - not power, so depending on how you're looking at it you will just see an earth from the ECU, or more accurately, from the fuel pump control module. Can remember if power is switched as well.

Crans Mentor

Crans

Posted
  • Author
Posted

So the earth and the power wire from the ecu both need to be connected to the switch side of the relay?? Pretty sure that exactly how I had it connected.

I'm running a deatschwerks 300L{H fuel pump and it needs as much voltage as you can give it. Im also running Deatschwerks 740cc njectors so im wanted to make sure fuel pressure is spot on.

Got 2 keys cut and 1 works so im mobile again. I will try and do the rewire again this weekend.

Torques Mentor

Torques

Posted
Posted (edited)

Yep,

The fuel pump gets + (12V) via the relay which is triggered directly by the ECU.

The ground side of the pump is connected to the FPCM (which in turn is some kind of floating ground if you will).

If I were to do this mod, I'd unplug the FPCM and bridge connectors 3 + 1.

No relay or anything needed.

I'm running the Z32 ECU, and this one does 3 voltage steps ..

Once that box fails, the direct wire is a good option :) I've had two die.... but agree that for many people its pointless. They just get scared when they see the lower voltage across the pump when the soft earth is switched in because they measure at idle or ign.

OP - the earth is switched - not power, so depending on how you're looking at it you will just see an earth from the ECU, or more accurately, from the fuel pump control module. Can remember if power is switched as well.

post-33912-0-07666700-1314612248_thumb.jpg

Edited by Torques
Torques Mentor

Torques

Posted
Posted (edited)

The pump is only reduced in voltage when the car is at idle, once things get in motion the FPCM switches over to full voltage.

I doubt you will need 300L/H at idle, so why bother?

The whole concept is that Nissan wanted to reduce noise from the pump when the car is stopped.

Personally I hate that whining sound and it bothers me.

(my car is also my daily drive and I also like my car to be 'neat' and fast) :)

So the earth and the power wire from the ecu both need to be connected to the switch side of the relay?? Pretty sure that exactly how I had it connected.

I'm running a deatschwerks 300L{H fuel pump and it needs as much voltage as you can give it. Im also running Deatschwerks 740cc njectors so im wanted to make sure fuel pressure is spot on.

Got 2 keys cut and 1 works so im mobile again. I will try and do the rewire again this weekend.

Edited by Torques
Brezza Proficient

Brezza

Posted
Posted

i'd be checking the earth, and making sure it is fine all the way to the pump.

i had a dodgy earth connection on my fuel pump through the tank lid and it wouldn't supply enough power to the twin in tank pumps i've got.

miga24 Enthusiast

miga24

Posted
Posted

first check the blue 15a fuse in the boot, than go to the fuse box below the steering wheel, its the A/T fuse, third one down on the right hand side 10A after that check the relay by taking off one from the Air con, than u shuld take the fuel pump and directly link the wires to the battery to check if its working if the above fail.

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