R33 Fuel Pump Wiring , Better Feed Retaining Fpcm ?

[discopotato03]

Hi all , I been reading about and looking into this fuel pump rewire business - and alternative fuel pumps as well .

I found in this thread a link to the R33 Engine Manual and it shows diagrams of how the various fuel pump control systems work .

http://www.skylinesaustralia.com/forums/topic/390739-fuel-pump-circuit/?hl=%2Bfuel+%2Bpump+%2Bcontrol+%2Bmodule

From what I gather they have ignition switched power via a 15a fuse to the fuel pump relay and the ECU earth switches the relay coil . Power is fed to the fuel pump and the pumps earth side is controlled by the Fuel Pump Control Modulator or FPCM .

It seems how this works is the return to earth is via a dropping resistor though the FPCM has an alternate earth return bypassing the resistor . The ECU must switch a relay to operate this bypass .

That aside , everyone seems to be rewiring their fuel pumps so the original power supply to the pump is used to switch a relay with a direct battery supply to the pump . Often the earth return is to the battery as well .

Now pump wise we can do better than factory but I'm not so sure that having the full 14 volts (or whatever) to the pump all the time is a good thing . People have concerns about high volume pumps circulating a lot of fuel and it returning a lot of heat to the fuel tank esp with stop start driving or long periods at idle .

It's this point that makes me wonder if the std system can be rewired so you keep the FPCM or similar but have newer and better wiring more suitable for big capacity pumps . I also wonder if the low voltage for idling can be lower than factory so real big pumps can be toned down volume wise for street duties .

SK reckons pump voltage is pretty much proportion to pump volume so you get about 3/4 of the volume at 9v that you would at 12v . Possibly 2/3 at 9v than at 14v .

I'm sure there are sparkys here that could come up with something if new wiring in the existing system couldn't cut it . Surely aftermarket ECUs can switch a bypass relay with certain conditions met and even if it screwed up you get enough fuel to get home .

Thoughts ? Cheers Adrian .

[Ben C34]

I am very interested in this also. I have been considering making a 2 speed controller run from my eboost 2 boost controller as that can switch based on rpm or boost. Using the factory stuff somehow would also be a good option.

[XRATED]

there are plenty of aftermarket fuel pump speed controllers/pwm that will handle more amperage than either of you could possibly need.

[Ben C34]

there are plenty of aftermarket fuel pump speed controllers/pwm that will handle more amperage than either of you could possibly need.

fair enough. Never thought to look. Any recommendations? came across this, very reasonable price, any thoughts? https://www.easyperformance.com/products/online-store/mode/filter/search/Fuel%20Pump%20Controller

[discopotato03]

Yes I've been looking at FPCMs and while the PWM regulated ones may look good controlling them is a bit more involved .

I don't mind the "dumb" Nissan style ones so long as you don't get the dreaded voltage drop in direct feed mode . This something that would be easy to fix if you had to wire your own bypass .

I'm just looking into Z32 300ZX TT FPCMs ATM and they are "three speed" compared to the NA versions two .

This is one aftermarket one I found a little while ago .

http://www.z1motorsports.com/product_info.php?products_id=4132

A .

[scotty nm35]

Most of the turbine aftermarket pumps won't fare well at low voltage, some even stall. Running a pwm controller will help but it's a lot of cost, and for what gain? It would need to be ecu controlled to have any hope of controlling the mixtures...

I would just run a cooler if you have fuel temp issues.

[discopotato03]

I don't ATM but I'm looking at higher volume pumps and I tend to think they would cause problems slothing around in Sydney traffic especially in warmer seasons . I like the idea of PWM systems but something has to control it and its something else to have to screw around with when tuning .

I looked again at the Vipec plug in blurb and it mentions R33 GTRs use a three stage FPCM so that's worth a closer look since I use their box . It could be a way of running say an 044 pump which is cheaper than the drop ins and toning down the noise and volume when its not needed .

A .

[WMDC35]

the later models didn't have the voltage drop at the pump like the r32s etc, the 044 should be fine intank on std wiring?

[89CAL]

Speaking of fuel coolers.... what are people using? I was going to just use a cheap trans cooler or something on the return side

[XRATED]

http://aeromotiveinc.com/products-page/accessories-electronics/16306-billet-fuel-pump-speed-controller/

$350 is the best and most cost effective way of doing it. Honestly $350 is nothing in comparision to what your likely to spend on your skyline. Just needs a tacho input and can be wired with an overide switch (think dash swith, boost reffrence switch etc).

If the controller is installed and adjusted properly, it isn't going to effect fuel pressure or mixtures..

After the initial set up there is not more adjustment needed.

Why is this so hard to understand??

[33GTRV]

Because the bloke overthinks everything to the point of disbelief. I mean hey, who cares about the 1000 people that have tried before him. The money he spends is pribably a new set of injectors. Next week he will hypothesise about how to play with voltave and resistance to gain 4cc out of stock injectors

[discopotato03]

Why go looking for known problems if they are avoidable . 1000 people may do the full voltage rewire and run an 044 - but that doesn't make it a brilliant idea .

I've been there before with hot fuel dramas and don't want a repeat problem .

Anyway contemplating an R33 GTR Nismo pump or an 044 ATM . The Vipec plug in can do ether the GTS25T two stage or GTR 3 stage FPCM and probably only needs one extra wire from the ECU to do it . If it's good enough for a GTR then can't be bad on a GTS25T .

[discopotato03]

Actually after a lot of searching on Nissan FPCMs it looks like they have issues over time . They act up in Z32s and whatever cars had Q45s in them . One person suggested that when fuel pumps age and lemon out electrically they can pull higher current and overload the FPCMs , which in turn get hot and go the way of overheated circuit boards . Like people mention here they get bypassed because a flat out pump is better than an unpowered one .

So I suppose the reliable fix is PWM control if you want pump speed control .

[Guilt-Toy]

Speaking of fuel coolers.... what are people using? I was going to just use a cheap trans cooler or something on the return side

been doing this for years... all it does is stops the fuel getting hotter for an extra hour or so... so it really just masks the issue.

i use a trans cooler from some car, i cannot remember what.

[discopotato03]

I asked a few people I know who have been working on road and in the past rally cars forever and the answer seems to be to avoid the complexity of PWM controllers because they introduce variables - more problems to solve .

I think simplest way is to cop the damage and buy a Nismo R33 GTR pump because one it falls in and two it isn't over the top capacity wise . My GTS25T is already using an R33 GTR in tank assembly which is different to it's original 25T one - these mount the larger pump higher and have a length of hose down to the filter sock . I'd be very surprised if this pump couldn't feed enough E70 to get to 300-320 wheel wasps .

Being a direct replacement means it's intended to live with the std GTRs current supply in as new condition . My pump was second hand and came as a complete drop in assembly ie from the lid down so must be 16 to 18 years old . The Nismo pump comes with a new hose sock and tank seal as well as the internal wiring and plug .

FPCM wise I'll keep the std one unless it has problems and we are going to check the resistances of all pump wiring and renew as necessary .

A .

[Dose Pipe Sutututu]

blast from the past (last year lol)

Ok I've installed my Walbro 460L and I know one day it will be drawing nearly 17~20 AMP of current at full song, provided the fuel pressure is close to 60 PSI (3 bar base pressure + 1.5 bar of boost = 65 PSI).

At the moment it poses no threat to melting connectors & wires as I'm only running a boring 0.9bar of boost which would only bring the fuel pressure to 56PSI on full noise, so the factory 15AMP fuel wiring will handle it just fine.

I am planning to ALSO retain the factory FPCM, however use the negative trigger from FPCM to trigger a relay to feed direct battery voltage to the pump when the FPCM is triggered. I will be using 12 gauge cable to a 40AMP horn relay connected to a 25AMP blade fuse, this relay will only ever trigger when the throttle is pressed pretty much.

I understand people say that low voltage kills walbros, however I've used older 255 pumps and left it in the original wiring setup for many years and nothing has failed.

Has anyone attempted that? I've done a google search but everyone seems to just ground off the pump.

[Dose Pipe Sutututu]

After some quick reading the stock FPCM has 2x negative outputs.. one going through a dropping resistor to produce the +10V or so and the other negative output going through no resistor.

These both then merge back into 1x negative wiring going back into the fuel pump, commonly people chop this wire and then ground it off to get a constant 13.8V to the fuel pump.

So, this is what I have planned (I will put my car to the test).

1. Disconnect the non resisted ground from the FPCM
2. Connect that to a relay ( as a negative trigger, connect the positive trigger to the fuel pump +ve signal & the other earth wire to the body & fuel pump directly)
3. Connect the positive of the fuel pump to a relay to for the positive power (fuel pump -> relay -> 25AMP fuse -> battery -> fuel pump positive trigger)
4. Bridge the factory dropped negative line back into the fuel pump's negative wire.

This means the fuel pump will NOT use the car's factory +ve wiring but only the car's factory -ve low voltage line, when it clicks over full noise it's purely running off 2x relays direct to the battery.

What do you reckon?

[GTSBoy]

You need big fat wire in the negative side just as much as you need it on the positive side. Current flows through all parts of a circuit.

[Dose Pipe Sutututu]

You need big fat wire in the negative side just as much as you need it on the positive side. Current flows through all parts of a circuit.

correct, hence the negative triggered relay for the full voltage..will have beefy earth wiring.

on idle, the current is very low as the fuel pressure is only at 3bar, theoretically only max of 15AMP (which the stock wiring will handle)..

so how it will work

fuel pump

+ ve: 40AMP relay & 25AMP fuse with 12ga wiring

- ve: 2x negative feeds, 1x stock low voltage for idle & 1x 40AMP relay & 25AMP fuse with 12ga wiring for full noise, triggered by the FPCM.

[Ben C34]

Does it really matter to have the pump control?

How much colder would the fuel be? that's the only reason I can see to run dual voltage as they aren't noisy pumps.

I mean if you pumped half the fuel around to the engine and back, would the fuel be half as cold? The way I see it, it couldn't as it has had more time in the engine bay to absorb the heat.

Someone smart help!

Edited January 6, 2014 by superben