Jump to content
SAU Community

Recommended Posts

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.

Link to comment
https://www.sau.com.au/forums/topic/375462-no-power-to-fuel-pump/
Share on other sites

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.

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

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.

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.

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.

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.

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.

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

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

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.

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.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • The ATTESSA is functionally identical to R34; there were a bunch of JDM models that continued ATTESSA including Fuga/Q70, Skyline/Q50, Cima etc as an option. All with Auto only and I think mostly for snow regions. AFAIK there were no AWD VR30DDTT sold in Australia - it is on my to do list to check regs for racing a LHD car in Targa/ATR/AASA/CAMS events because if I can get the auto to work it would be interesting to run a 4wd car The Ecuteck TCM tuning is the same model as their ECU tuning, they already have it for R35 and Dose's favourite, BMW. You buy "points" to allow your computer to be tuned, buy either a bluetooth (phone app) or bluetooth+USB+Key (phone and PC) dongle, and pay for a tune that will be locked to your tuner ( ). You can also access the tuning software yourself but 1. it is mega expensive and 2. these computers have a billion parameters that intersect, so how could you ever spend enough time on it to get a decent result.
    • Or, is it a case of what it is like owning an R series Skyline? NFI what the previous owner has done or fiddled with... Ha ha ha After reading through this thread, I went on a bit of a research about the Q50/Q60. Now I'm quite intrigued by them! Is the AWD in them more like a WRX where it's always AWD, or is it more like the ATTESSA in the GTRs? By the sound of this TCU tuning, this sounds like a case of someone has made some real software for it, and you just need the right piece of hardware, and then you license that specific vehicle/TCU. Or is this a case of the software will be really expensive so only a few tuners have it, and you still have to pay a license per vehicle?
    • By popular demand.. it was a coil. Got my hands on 1 new OEM coil, replaced with the one that made the less noise difference when I unplugged it while the car was running and started the car up. No stutter and the engine light was gone. I guess I’ll buy the other 5 they have lol
    • No, code 21 is very straightforward. It can only be the things described in that diagnostic flow. In fact it has no way of knowing that the spark plug resistance is out of spec.
    • Hi, SteveL Thank you very much for your reply, you seem to be the only person on the net who has come up with a definitive answer for which I am grateful. The "Leak" was more by way of wet bubbles when the pedal was depressed hard by a buddy while trying to gey a decent pedal when bleeding the system having fitted the rebuilt BM50 back in the car, which now makes perfect sense. A bit of a shame having just rebuilt my BM50, I did not touch the proportioning valve side of things, the BM50 was leaking from the primary piston seal and fluid was running down the the Brake booster hence the need to rebuild, I had never noticed any fluid leaking from that hole previously it only started when I refitted it to the car. The brake lines in the photo are "Kunifer" which is a Copper/Nickel alloy brake pipe, but are only the ones I use to bench bleed Master cylinders, they are perfectly legal to use on vehicles here in the UK, however the lines on the car are PVF coated steel. Thanks again for clearing this up for me, a purchase of a new BMC appears to be on the cards, I have been looking at various options in case my BM50 was not repairable and have looked at the HFM BM57 which I understand is manufactured in Australia.  
×
×
  • Create New...