Forums/Z31P/z31-performance-upgrade-forums engine-management/FAQ - Fuel Pump Circuit for full power high pressure
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DrewZee87T: (2006-06-07 00:45:06)
I have had a number of email requests for this and keep running into people (usually JWT types) that are having problems "keeping it up" in terms of fuel pressure, due to maintaining the stock fuel pump power supply. I know this is old hat to many of you, but perhaps someone will get some mileage out of it. Feel free to linkinate or post anywhere you want.
The very important thing to note about stock Z31 fuel pump circuit is that it does NOT supply a constant 12 v to the pump if you leave it stock. The ECU controls how much ground it gets, and varies the voltage. With my fuel pressure guage in the car, its obvious just how much it varies your pressure. You need to have a constant source of nice clean 12v to the pump in order to maintain the increased base pressure and anything beyond that. Here's a simple circuit modification that corrects the fluctuating pump voltage problem. I have mine mounted back in the spare tire well.
What you need:
Standard relay that is a normally closed switched side. (I am using layman's terms here)
10 or 12 guage wire
Four female spade connectors
Solder iron, solder, electrical tape orââ¬Â¦.crimp connectors and shrink tubes
1/2 of a brain (optional)
A sheetmetal screw (optional)
Take a blue Nissan relay (everyone should have a box of these things lying around - they are very useful, and "free" at any junkyard), or any standard relay. What you want to do is to create a ground source that is controlled by this relay. I have tapped into my power antenna power supply to activate the switch, since I don't use the power antenna, you can also tap into the power supply for the fuel tank sending unit, or even the power supply to the fuel pump itself (this is the most efficient, but I didn't think of that until I had already sourced it from the antenna). Either of those are hot signal +12 when the ignition is on, and the ecu ground will be controlling when the relay opens anyway. So you activate your relay with that power source. Cut the ground wire that runs from the fuel pump through the harness to the ECU (umm-yeah it is black it think, use an ohmmeter to make sure). (leave plenty of room to solder connectors on both sides). (Use fairly heavy guage wire 10 or 12) Solder/crimp a ground wire to the ECU side of this ground wire and run it to the power supply (the actuator) side of the relay (this will be the ground that completes your circuit from the positive hot ignition source earlier). On the fuel pump side of the ground wire, solder in a wire and connect to one side of the switched section of the relay. On the other side of the switched section of the relay, run another heavy ground wire to any good body ground. I just use one of the screws that goes to the cover on the sending unit.
So now what you have is that when you turn the key ON, the relay gets power from the positive source, and the ECU activates the ground side. This throws the relay switch that allows the body ground to reach the fuel pump and complete the circuit.
We have maintained the fuel ground to the ECU so it thinks everything is normal and just does its thing - it's loaded with the power supply from the relay. Now you will have 12volts full power to your fuel pump whenever the car is on (for five seconds) or running. The reason you have to use a relay is since the fuel pump positive is always on, even when the car is off. The stock fuel pump circuit only gets completed by the ecu when the ecu grounds that wire.
There are other ways you can design this circuit but this one has built in safety: If you wire your pump to run full time whenever the ignition switch is on, you could find yourself in a situation where you are upside down unconscious in a ditch and your fuel pump is still running. NOT GOOD.
This circuit allows the ECU to control the relay. The ecu is pretty smart, you notice how on turning on the key, the pump runs for five seconds and shuts off. Similarly, if the engine stalls out, the ecu shuts off the pump. So by wiring it this way you don't have to listen to the pump running if you are just checking something with the ignition on, and you reduce the chances of dieing in a fiery blaze if there is an accident, but you still get your full power to the fuel pump.
Here is a cheesy diagram:
http://devster.net/roni/86z/Z31%20Fu…plications.doc
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MikeZ: (2006-06-07 01:47:04)
Thanks for the write-up Drew.
Jason84NA2T: (2006-06-07 03:11:55)
Thanks for the writeup Drew! Very good information for people wanting to do this modification. I would have to say the single biggest benefit is no risk of burning out the fuel pump circuit in the ECU. People have reported if you put in an aftermarket pump you can fry this circuit… I'm not exactly sure why because it runs off a relay anyway, but I have always been confused about how this voltage supply feature really works. The ECU actually steps up the voltage to the pump, supplying as much as 13.4v in most conditions shown here from the FSM:
[archived image: pumpvolt.JPG]
While this modification has worked for MANY others (i've heard at least 10 people say it made a big difference), I tried wiring my walbro to a solid battery source and actually noticed no difference in either the fuel pressure (using a mechanical gauge mounted outside the car) or drivability. Very strange.
DrewZee87T: (2006-06-07 05:11:54)
Hey Jason,
I cannot say except for personal experience, it could be a JWT only issue since they dick around with the fuel circuit and introduce other weird problems as well. I experience reduced voltage. The FSM 13.4v would appear to be alternator voltage, since the ecu just controls ground, then you have system voltage going in. 88T fed ECU in my case, but completely whored by jwt. I have had good results and a few others also using this type of circuit.
You will note in the FSM figure you posted it says 9.4 to 13.4 volts, except as above - if you look at the conditions listed in the above it refers to starting, cold running, warming up, and running quite hot. Its hard to determine whether the operating range between 122F and 194f is included in the 13.4v logic. I don't think it is. In all other running conditions you have voltage of 9.4 to 13.4 fluctuating. They should use decimal points.
The diagram shows a direct to battery, but in practice you are using all the harnesses that are already there, so its actually hitting the same fused fuel circuit for the +. I hate to have diagrams that have stuff not terminated to something, hence the battery in the diagram. I don't do electrical shit for a living (as you probably surmise) but I am really handy with Visio [archived image: smile.png]
I think the ECU controls voltage in an attempt to reduce pump wear and pressure when its not required - e.g. idling, under cruise or decel. That would reduce system load, and increase pump life, and also reduce the strain on high pressure hoses. Probably Nissan ran some shitty testing numbers on production pumps and put that in to prolong life "long enough"....Without this mod in three cars - 87T, 87na-T, and 86na-T, using the same brain and drivetrain, I get voltage drop. I like to body swap a lot apparently.
It's a ridiculous simple mod, about up to my speed.
Peace
G-E: (2006-06-07 08:12:44)
um actually.... I will simplify it further
take the hot side and connect it to the relay's coil hot and switched hot directly, then run the switched ground to the pump hot and the coil ground to the ecu....
if only you knew the power of the darkside....
DrewZee87T: (2006-06-07 18:13:52)
Let us know how that works out.
Bring extra fusible links [archived image: smile.png]
Stinky: (2006-06-07 18:32:01)
Huh?
Here's my take on this. Basically the ecu does one of two things with the fuel pump.
A) it provides partial voltage by providing a limited ground to the fuel pump directly from the ecu. Pump runs slow.
B) it sends a signal to the fuel pump relay to provide a direct ground to the pump. Pump runs full speed.
I did some testing a while back and it seems the pump goes to condition B near 3000rpm.
Anyway, instead of adding a relay why not just use the existing fuel pump relay and wire the signal wire to a different source? I believe thats what JWT attempts to do. Anyway it shouldnt be hard to find a wire (maybe even the wire for condition A that would switch the relay and provide full power to the pump. Swapping one wire sounds easier than all that other stuff. Am I missing something?
G-E: (2006-06-08 00:39:49)
actually I forgot to say run a new ground to the pump
the idea was to keep the relay triggered by the ecu but the pump voltage directly from switched power
and about them fusible links, since the efi wiring and relay aren't asked to do anything they don't already do, there's no chance that wiring the pump on constantly will fry anything
DrewZee87T: (2006-06-08 05:26:14)
Ok, yeah that makes sense
Sorry I didn't get the previous post. Anyway, I am not interested in playing the games about who is smarter. What I posted works, what you posted probably works too, and Stinky wonders why anyone cares. I will keep this in mind when posting in the future. I am not a master technician or any kind of mad genius of the zcar and I figure shit out and find what works, usually the hard way. Take it, leave it, if it's dead wrong let me know.
Jason84NA2T: (2006-06-08 05:29:26)
Re: Ok, yeah that makes sense
I don't think anyone was criticizing you at all for posting the information about the way you did it. In fact, I'm down right grateful you took the time to type it all up, make a diagram and post it for others to learn from.
It just spurred a discussion is all, I wouldn't take it as a bad thing.
DrewZee87T: (2006-06-08 05:50:16)
/me sensitive today - sorry
I had a wack day trying to defend plans on how to restructure 23 billion dollars worth of contracts to a bunch of very unfriendly government people whose jobs and seats of power may be impacted. I have been beaten up pretty bad today.
Z's are my hobby [archived image: smile.png] I see the potential of the alternate suggestions and the pragmatist says "whatever, this took ten minutes and works". I think the fuel pump thing will impact other projects, so the discussion on the subject is good. Stinky is correct to address the problem directly at the first relay and make it a "one wire switch" mod that can be just another instruction step in the basics, however I haven't had any time to look at that and probably never will. I haven't even attempted to get into the first relay, just to work around a problem.
Peace
G-E: (2006-06-08 07:39:41)
the ecu switches the ground to "on" and varies the resistance to slow the pump down, having an alternate source of power for the relay doesn't help, and having a pure ground to the relay will prevent the ecu from being able to shut it off
so my diagram is correct, always,supply the power to the relay, and use the ecu to trigger the relay ground, relays will generally trigger at anything above 7 volts, but the lowest it could see would be 9 and I'm very sure that will make it click
all this can be done by modifying the harness at the relay and at the blue plug from the pump harness, and once you have it re-taped/loomed it will look factory too
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CAG8OR: (2006-08-20 16:36:04)
Just curious if anyone here has tried this unit from MSD? It sounds like a good idea for our application, especially for people maxxing out their 420CC injectors. From the MSD site:
Fuel Pump Booster Adding a turbo or supercharger to your engine is a great way to improve the power of your car. But you have to remember that when more air is being pushed into the engine, the need for additional fuel raises proportionally. Meeting these new fuel demands could mean larger injectors or ECU programming, both which can be pricey. This new Fuel Pump Booster is the economical (and easy) answer for your engineââ¬â¢s new fuel demands. The Booster will supply the electric fuel pump with increased voltage in relation to the manifold boost pressure. As boost pressure increases in the manifold, the MSD Booster will increase the voltage to the electric fuel pump. The amount of voltage is adjustable with a potentiometer from a range of an additional 1.5 volts to a maximum output of 22 volts over a range of 5 ââ¬â 30 psia. Fuel Pump Booster PN 2350 NOTE: Not for use on Pulse Width Modulated EFI systems (no return line)
Jason84NA2T: (2006-08-20 16:48:34)
Just like the Boost-a-pump, those really help out only if your fuel pump is maxed out. The stock ECU gives the fuel pump up to 13.5v anyway, so I'm not sure there would be any benefit besides another cool looking box in the engine bay.
Edit: can EFI pumps really handle 22v for very long? wow.
G-E: (2006-08-20 17:03:15)
btw I was looking at the fsm, the easiest way to accomplish the full pump voltage is put the yellow-black on a switch to a good ground, use the pump priming relay manually for constant battery voltage
and if you clip the ecu ground for the pump, the switch will become an immobilizer
Stinky: (2006-08-21 02:27:13)
What sort of problems have you guys heard of people having with the jwt pump mod?
jeffp: (2006-10-12 23:45:23)
JWT fuel pump mod
I have run two systems now of the JWT modified ECU. I don't know where you guys get your information about the ECU, but they are incorrect.
The Z31 ECU provides a GROUND to the RELAY coil windings. So to hook that part up correctly, you find the wire from the ECU (pin16) this gets connected to the relay coil. The second relay coil wire gets hooked to 12 VDC or the battery. This will energize the relay when the key is turned on, and denergize the relay with the ignition off or ACC positions.
The second thiny you need to do, is first of all get a new Bosch or equilivant relay that is rated for at least 30 Amps.
- arrow:
NOTE: I have tested the Nissan 20 Amp relays, and the Bosch 30 Amp relays. I did not like the results, the Nissan relay would not sustain a 20 AMP load for extended periods and not becone to hot , and I was seeing a 1 VDC drop across the relay contacts, not good. So the pump would be getting only 11 volts if the battery was at 12 volts. This is not a good option for the fuel pump. The Bosch Relay could sustain a 20 AMP load, it still did get a little hot, but manageable for extended periods, provided the spade lugs were tight.
- wink:
So you get a good #10 wire, I dont recommend #12 it may be ok to use for short runs. connect the battery up to the common lug of the relay. connect the N/O normally open lug to the fuel pump positive.
Now to overcome the modulated speed of the pump and have it run at a continious rate: remove the ground on the pump, and install a ground wire to chassis ground and the pump negative. This will overcome the modulation, and I would highly recommend this. You will need a steady flow of fuel to make tuning easier, and to ensure you have good drivability on the street. Also, fuel flowing through the rail and back to the tank is then cooled, you can think of the fuel somewhat as a good heat sink to keep the injectors cooler and the rail cooler. The ONLY reason Nissan installed a modulated pump configuration, was to decrease the noise of the pump @ idle.
That should clear that up.
The MSD box, YES it does work. I went through hell trying to get my car to flow enough fuel when I went to 4 BAR static fuel pressure with the 420cc injectors. The pump would fall on its face after 78psi and the flow would slow down to the point the pump was not able to supply enough fuel at WOT.
I opted for the Nissan twin turbo pump, which of all my testing, calling, and inquiries, turns out to be the very best pump you can get, provided you have an in tank fuel pump, or if like me had an external pump and retrofitted my pump in the tank, not fun at all, total PITA, but it works now after three revisions LOL. I was able to get 3300cc's a minute @ 90psi with that pump, and I tested it in line through the whole system.
So back to MSD, My friend is running the Bosch 944 twin turbo external pump in his car. He also had the same problems with the fuel pressure. He installed the voltage stepper box from MSD, and that solved his problems 100% so YES it works.
You know I know Clark and Jim a little better then most, and I don't consider their work hack work at all. They do a good job, of modifing, and retrofitting upgrades to the Nissan cars. I am currently working with Clark on my car to work out the bugs with the injection for a 600Hp L28 turbo application.
anyway, have a good day. [archived image: smile.png]
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G-E: (2006-10-13 03:36:20)
like I said, if you also connect the pump priming relay ground to the ecu's pump ground - a simple cross splice - then you'll have more grounding and full ground voltage at all times
Black 89Turbo: (2006-12-27 01:18:14)
so if your ECU throws a fuel pump circut code u can by bass the circut by doin this mod.
Spazzymcgee: (2007-09-13 16:39:32)
Got a question for you guys about this
I have it to an arming switch which I can flip on and off when ever I want
I have question tho about the fuel pump
How long before it will just crap itself getting a full 12V's? Or will it not?
Sorry I'm a newb about this and all
But rather be safe than sorry.
Because I just dont want to be driving and opps there goes my fuel :lol:
Oh and with my bypass, I did it with (2) 10gauage wire, and 4 females, and looped it over the switch and back into itself, instead of using the relay any problems would come of this does anyone know?
Z-day: (2008-04-06 13:24:48)
hey great info. one problem. i dont think words. could you make a diagram wire color and whatnot and a parts list. also wouldnt you only really want the pump at 100% at or starting near WOT? sort of ike the way the clutch safty switch is with the starter or the brake lite switch on the pedel? if so could I do a switch on the pedel for a closed circult @ WOT or make it ajustable so that when i get to the trottl point where its enough to boost switch from computer variable to full on? it would effectively be how the system should have been.
SATAN: (2008-04-06 14:06:16)
Having the pump run at 14 volts all the time is just fine. Hopefully you are seeing more than 12 volts with your car running if you have it wired on a switch. The pump running 14 volts all the time is not going to hurt anything so long as the pump always has fuel surrounding it to keep it cooler. This can be a problem if yo are running 1/4 tank of fuel or less.
Z-day: (2008-04-06 15:41:38)
my sender is f%^*ed
actual-----gague
F-----------F
1/2
1/2----------E
E-------------
so yes cuz the light still works! so do you thing my idea would work? i could also use the z32 pump witch would solve everything but the f^%! gave me an n/a one.
SATAN: (2008-04-06 15:49:23)
[quote]Z-day wrote:
This can be a problem if yo are running 1/4 tank of fuel or less.my sender is f%^*ed
actual-----gague
F-----------F
1/2
1/2----------E
E-------------
so yes cuz the light still works! so do you thing my idea would work? i could also use the z32 pump witch would solve everything but the f^%! gave me an n/a one.
Sure you could make it work. It is just a lot of unneeded crap. You have a fuel pressure regulator for a reason. You can run the pump maxed out. Any additional fuel that is not needed will just get returned to the tank. As far as I know some pumps cannot run at less than the specified voltage. Problems arise when you do so.
Z-day: (2008-04-08 06:11:55)
thanks for you help on both posts satan
zraver: (2008-04-30 02:52:03)
I did something similar when a drive transistor in my stand alone ecu went bad. However I used a switch as the ecu was running the pump full time. While the switch is useless if I am rubber side up and taking a nap, it does give me a nifty theft deterrent. Unless you know where the switch is and what to look for you won't start my car. well you might start it, but it will die in 2 seconds and not start again.
Some one doing your mod could add a switch and get the best of both worlds.
Careless: (2009-01-29 15:30:48)
This has alot to do with the other question asked about running @ 22v.
My father used to repair fuel pumps and small motors throughout college to learn more about his field (ac/dc motor technician/engineer/teacher)… he's seen quite a couple of weird things. Back when wiring on some older cars or first-model vehicles were using newer fuel pump setups and new wiring techniques as science experiments from various car manufacturers, he noticed a few things…
He's told me that if your voltage drops anywhere below 50% of rated output, you're driving on the thin line between having a low voltage that will create enough heat to destroy the windings and not pump enough fluid to dissipate the heat. Whereas running a pump at over 175% rated voltage would the voltage you have to worry about on a mid-sized car with about 5 to 10 litres left (highly based on tank sump design/pump location… internal/external…yada yada).
If anyone knows about AC/DC motors, he's the guy.
Reading books about them while waiting for a quad-bypass (twice)
Dedication, I'd say.
sporklift: (2009-06-05 06:23:59)
That's neat, I was thinking about putting an inertia switch in the fuel pump circuit when I get around to putting the standalone in. One reason being for safety and also to bump it open when not running so that nobody can steal the entire car unless they are actually smart and look for the switch.
Amadeus: (2009-07-20 17:01:34)
Is this mod only helpful if you have the JWT ecu, or will it help if you put in an aftermarket pump like the walbro?
Loomis: (2009-08-21 08:45:25)
Awesome thread… I shoulda came to this board to begin with! lol
Question.. I have a 24 hours of Lemons Z31 Turbo.. and I've ruined 2 sets of heads.. the last set running lean enough to eat two exhaust valves. Motor is stock. Cooling system is in excellent shape. All sensors are new except the O2.
Is this mod worthwhile in a stock application? Its lookin like I'm starvin for fuel. Fuel pressure gauge on the motor starts at 28psi (idle) and goes to 37 (turbo should hit 44 under boost) as soon as you touch the throttle, but I cant see whats happening under load (gauge at regulator).
I'm thinking a JWT regulator, and this mod would do the trick. Any thoughts?
Also looking into the CHTS mod, and simply leaving the O2 unplugged. More thoughts? lol
This car is to be raced only, never smogged.
Careless: (2009-10-12 18:19:43)
[quote]sporklift wrote:
I did something similar when a drive transistor in my stand alone ecu went bad. However I used a switch as the ecu was running the pump full time. While the switch is useless if I am rubber side up and taking a nap, it does give me a nifty theft deterrent. Unless you know where the switch is and what to look for you won't start my car. well you might start it, but it will die in 2 seconds and not start again.
That's neat, I was thinking about putting an inertia switch in the fuel pump circuit when I get around to putting the standalone in. One reason being for safety and also to bump it open when not running so that nobody can steal the entire car unless they are actually smart and look for the switch.
Inertia Switches were the root cause of many lincoln and fords being sold to back to car repair shops because they had many headaches, and Ford was very selective about who they instructed to do the simple "click" and also didn't make it very apparent in the owners manual either. Once municipalities and road/highway departments started to include speed-humps or speed-bumps in every new suburb, there were many people left with their lincoln stuck just beyond a speed bump with no way to start their car.
The best thing to do is mount the relay in an inconspicuous spot, and if you're worried about someone fucking off with your car, just pull they relay. Heck, even give it 1 foot of wiring so that no one knows where the hell it connects to.
Distortionfile: (2009-12-21 07:35:53)
I did this mod tonight and was very satisfied with the results, but after reading back over I feel one thing is amiss.
I basically just cut off my connector between the pump and harness. Then I reconnected the 12+, and ran a lead from that to the relay coil. Then I twisted the two ground sources together and ran those to the other side of the coil. I ran a ground to the body and switched side, as well as the switched side back to the pump.
It works great, I can hear the pump humming away. My only concern is that I have somehow failed to retain my safety feature. When I key on, the pump is running.
Now, My wiring system is modified, both body and EFI, so it may be a result of something I did. The cars previous owner had a penchant for running poorly secured wires across the whole car, so I was left with some cleaning up to do, and I got enthusiastic about it.
The end result as far as I can tell as it relates to this situation is that my 12+ ends up being a switched lead, not a constant. When the key is off it is not present.
That however would not affect this. Before installing the relay I had a normal 5 second prime at key on. Now it's just on. It does however sound much better, even than it did on the normal relay. It didn't phase me at first, but then after reading the thread again I feel differently.
I would like to add for those concerned about the longevity of their pumps with this mod that fords have always worked this way to my knowledge, and there pumps last as long as any other cars. The biggest issue I had with Fords and fuel pumps was relays either being weak or getting stuck on.
RockinRickus: (2010-03-03 22:36:39)
I would like to thank Drew for this write up. The MOD worked great, my Z has never run this good!
Careless: (2010-05-30 04:28:11)
Did this mod today.
I think this would save those doing this mod a lot of time if the instructions were written a bit clearer, and perhaps some colours of the wires to make connections/disconnect were added to the tutorial.
I'll see how this works tomorrow when I take it for a spin.
NissanEgg: (2010-05-30 04:57:55)
Hey Raff, make a better detailed schematic. You are pretty good at doing those things. I will be doing this soon.
Careless: (2010-05-30 06:10:34)
[quote]NissanEgg wrote:
Did this mod today.
I think this would save those doing this mod a lot of time if the instructions were written a bit clearer, and perhaps some colours of the wires to make connections/disconnect were added to the tutorial.
I'll see how this works tomorrow when I take it for a spin.Hey Raff, make a better detailed schematic. You are pretty good at doing those things. I will be doing this soon.
Thanks. [archived image: smile.png] I have design job to do for someone here before I can make time to draw schematics for this circuit.
My only question regarding this is whether or not all the fuel pump wires are the same colour for each year??? Anyone know?
I did not cut any wires in my install… I simply de-pinned it from the connector and ran the ground wire the other way, and then tap-spliced into the +12 and ECU signal ground. If I ever want to wire it back to stock or test a fuel pump for operation, I would just need to take out the relay and plug the fuel pump into the main harness connection, and it will work like factory. Actually I wouldn't even have to take out the relay, but its a simple step.
Careless: (2010-06-02 15:20:32)
I would like to update and say that my car is indeed running better with this modification. I can attribute that to having a known boost leak, but the car isn't a complete slug anymore.
When I get my wideband installed, I may reverse the connection and do 3 logged pulls and then re-connect the unit and do 3 more logged pulls and average out my AFR's.
I believe most of what this overcomes (aside from having to attempt to tune fueling with poor granularity of the stock circuit) is that it may provided enough pressure to force any gunk in the lines or in the injectors to break free in some respect, or break it down better.
Just when I was suspecting that my fuel pump was coming up short (heck, it's 23 years old as of this month), I found this to solve the snap-throttle response where my car felt like it was wondering what to do when opening the throttle.
With my excessive backlash in my differential (being swapped to CLSD this week), it's been a good indicator of how hard the car lurches forward, as the resounding clunk has been a lot louder when stabbing the throttle. I'm just waiting hoping my differential lasts 3 more days and doesn't shit the bed before I get around to doing some swappage.
Thanks for the writeup!
blueridgespeed: (2010-08-05 01:23:18)
So CARELESS - can you let me know the best way to do this mod for a 85 turbo? I ask because I'm working on a swap into a 510 and my engine/tranny/ecu/fuel tank-pump were all retained from a 85t donor, and transplanted into a 510 tube chassis. It's taken me YEARS to build the tube frame, but the engine has always started and run. That said, I've had 1/4 tank or less fuel FOR SURE during this whole time, since I am pulling the tank out and in repeately for fitting/welding.
I no longer get the fuel pump hum when I turn the key - doh! And she won't "fire" now despite confirmed spark at the plug wires.
You mention that the voltage mod worked well despite the "23 year old pump"....
A few weeks ago it started and ran fine, but yesterday, no go. Yesterday, I had a fuel pump whine but she wouldn't fire up. Today, no fuel pump whine.
So I'm wanting to confirm that I have adequate FUEL. Um, I did add a few gallons of fresh 93 to the tank to be sure that wasn't the problem....
HELP ME!
Thank you all in advance for any help or well-deserved ridicule!
blueridgespeed: (2010-08-05 01:41:39)
Vg30et 510 hotrod update - she runs! (well, until today). The 85t drivetrain is *stock for now - but intake and exhaust are farbricated and thus should flow better than stock. I sectioned the turbo elbow to reduce the 90-degree bend, then cleaned up the stock downpipe mounting flange and fabricated from there with 2.5" mandrel-bent, - no bend's sharper than 45-degrees were used…
roastin300: (2010-08-15 22:43:34)
I just ran the relay and wires. Waiting for a filter to get here to actually drop the pump in the tank.
My issue with this is the wire coming off the ECU for the fuel pump is not JUST a ground (PIN 118 I think it was). With my test light it seemed to operate as a power and a ground depending on if the car was running or just had the ignition turned on.
I ended up wiring into the 12V source in the hatch that originally feeds the stock fuel pump, and this is what triggers my relay, and the relay is always grounded, rather than the other way around using the ECU to ground it and having 12V at the relay constantly. I do not have the 5 second prime and then turn off anymore though, its always one once the key is turned to the ON position. Not a big deal, but would be nice to retain the 5 second prime only if i ever need to have the key at the ON position for any reason. I will just pop the lead off the relay in the hatch if this is the case.
blueridgespeed: (2010-08-19 15:44:48)
As roastin 300 has pointed out, the wiring to the fuel pump is a little confusing. There are 3 wires all the way to the plug/connector at the pump, then 2 at the pump. Does anyone know where I could find more info on this?
I searched and only found my own thread and a few non-related ones.
88sinZ: (2010-10-16 03:15:10)
Tell me why if i have 14ga wiring rated at 17amps, and my fuel pump will be pulling ~13.8 amps (which is 80% duty for for wire rating) i should run a 10ga or 8ga… Also having a 15amp (88% duty) inline fuse.
300zxturboftw: (2010-11-18 23:57:26)
Hell I would just wire 12 gauge and call it a day for peace of mind. With your set up it seems it should run fine though. I could see someone using 10ga but 8, really? lol.
88sinZ: (2010-11-19 05:53:47)
Phuck it I already wired 8ga to + and - side of the pump, had to enlarge the wire holes in the mouting plate to feed thoes fat wired through
JeffSly: (2011-02-21 00:36:51)
Okay, going on 5 years later and I'm still not sure there was a definite agreement on what works here (or how this maybe relates to the stock wiring being undersized for some pumps, but that's off topic and elsewhere). So, I want to sum this up in one question and see if someone(s) can let me know if it will be happy since my car is in project mode and I can't exactly test, but I'm into this now for other reasons. So, please, for anyone who has been over this well enough to know for sure here is my question.
If you leave the stock fuel pump relay and wiring harness to the fuel pump alone, and cut the wire at the ECCS pin 108 and splice it into ECCS pin 20 will this provide full voltage to the pump at all times when the brain thinks it should be running (and only then)?
I'm sorry if that was said elsewhere or earlier in this thread but I'm trying to be clear. Diagrams would be great but can't do that now. I'll summarize anyway: the way I believe this worked as explained in the '86FSM and please set me straight if I'm wrong. Fuel pump is connected to fused power on hot side all the time (with key on or not I don't care). Fuel pump ground then comes either through fuel pump relay for the first 5 seconds and under some other conditions for full speed operation, or else ground comes through the ECCS varying from 9.4-full voltage to slow the pump. The stock relay is switched on by pin 20 from the ECCS on the ground side of the coil. I want to tie the other pin from the ECCS to here and leave the other end of this wire (from brain to fuel pump) cut. This way the existing relay will pull in with ground from either condition from the ECCS and all the stock wiring is intact except for one cut wire spliced into a nearby uncut wire near the ECCS. Any problems with this? I'll be running a Walbro or similar and aftermarket fuel pressure regulator.
Careless: (2011-02-21 02:40:44)
Im on my phone, so ill keep this short. I cut the eccs ground control wire. Wired that to 85 terminal on the relay. Use a tap splice to wire the 12v hot to the 86 terminal on the relay. This makes the relay close when the eccs is grounded. On terminal 30 you wire a 10 guage wire to the body. On terminal 87a (normally opened), you wire it to the cut eccs wire going to the pump.
When the eccs sends varied ground to the 86, instead of modulating the pump current, the relay closes its connection- 87 (which is not connected to anything) switches to 87a and the full voltage circuit is made via the ground connection that is made thanks to the relay terminal 30's ground connection. Its essentially the same as sending power to a rad fan, except you're sending ground instead of power via the body instead of the battery.
Make sense?
If the question is "will this work for a wally or higher pressure pump?" Then you need to run a brand new 12v from the battery or another circuit that can take the additional load.
JeffSly: (2011-02-21 08:54:48)
Thanks Careless, yes absolutely makes sense. What doesn't make sense (to me only probably, I am likely some form of undiagnosed OCD in relation to stuff like this) is that the car now has 2 fuel pump relays. So humor me for a second… The stock relay has 12V hot on the coil and passes straight ground to the pump on the switched side just like what was added with the new relay. It needs ground to switch on, which it gets from the ECCS on the other pin for first 5 seconds etc. So either relay needs to see ground to turn on the pump, is there any problem in connecting the 2 ground sources from the ECCS together on one relay?
Aaaand the other part I'll have to take a closer look at the wire size and if anything else is on the fuel pump's fuse before I comment, but the wally is what I have in mind. The baddest wally on the wally chart claims just 17.0amps at 13.5volts and 130psi though, and 8-12amps at more reasonable pressures. Not so far from the stock 10A fuse. Is the wally chart lying?
JeffSly: (2011-03-28 03:26:46)
Sorry for kicking a dead horse here, but:
For review, here's the fuel pump wiring as per FSM, skip it if you're familiar:
[archived image: fuelpumpcontrol.jpg]
The fuel pump wiring is 14ga. and fused at 10A. Assuming I'm good with that, does anyone see any problem with doing this (schematic below) instead of adding a second relay as has already been discussed?
[archived image: fuelpumpcontrolblue.jpg]
JSM: (2011-06-22 01:26:05)
JeffSly, thanks for posting that. I'm such an idiot, for whatever reason I never saw that page past the first 1/2 online. I need to buy an actual book.
Aside from saftey concerns I can not for the life of me figure out why we want the ECU to control the voltage to the pump. The fuel pressure regulator will adjust on vacuum alone. I think I'm going to just run power from the 10A fuse block as the source, to a standard 3 wire relay and forget pin 108 and 20 alltogether. The reverse grounding is really messing with me.
I'm puting a 300zx harness, MAF, Coil and ECU from an 86 turbo into my 74 260z.
michaelp: (2011-06-22 13:42:48)
Because any pump better than the stock one will cook the old ass OE wiring, but not the 10A fuse…
JeffSly: (2011-06-23 06:36:18)
I can't completely argue with this, because I know it's happened, pictures exist etc. Worse my car's nowhere near ready to find out for myself, but the high-flow Walbro's at stock pressure shouldn't exceed 10A by much if anything according to anything I've found ("high-pressure" version: 7.5A @ 13.5V and 40psi flowing 70 gal/hr, for example). Why shouldn't I expect an old ass 14ga wire to stand up to that?
Careless: (2011-06-23 06:40:20)
make sure the wire ends are free from corrosion and cut them back if you're unsure. if it's 14ga wiring it should be ok for that amperage.
JeffSly: (2011-06-23 07:13:42)
Well since the thread is momentarily revived, I guess that's the part I'm curious about. I'd rather it be 12ga, don't want to rewire for no reason, and really don't want to rewire after the project is a car again. So…ideally I guess I need convincing that the stock wiring, in perfect condition, doesn't handle the current it was fused for, or that the posted numbers for Walbro online are garbage. MikeP, I'll thank you in advance for that so I can shutup and wire it with some headroom.
JSM, since I skipped over your post I would say the safety concerns are valid and if it were me I'd keep the grounding indirectly through the ECU part. By connecting both of those pins to the ground side of a relay coil you'll have full power whenever the pump is supposed to be on (i.e. first 5 seconds only if you don't start the engine, not if you're upside down).
JSM: (2011-06-23 12:41:45)
I think I got it figured out now. I saw MicahelP drawing in another thread that got me the answer I needed to wire in the rellay through the ECU. I'm just not used to the ECU acting as a switch to ground. I think you only want 108 pin, not 20. Pin 20 above is what is regulating the power. I'm just going to leave it cut and unused. It may cause problems to the ECU trying use them together.
JeffSly: (2011-06-23 16:39:07)
Take another (closer) look at the FSM page posted above. ECU providing the ground takes a second to get used to I agree, especially when it starts varying the voltage level through that ground reference but pin 108 is the varying one providing voltage reference of 9.4-full. Pin 20 is just on-off ground reference for the relay. The questionable thing to me in the stock 300zx wiring is why there even is a relay, which maybe becomes the important thing for you with the engine swap, so to be perfectly clear: The 300zx has a fuel pump relay in the passenger side b-pillar area behind the door, it's wired to switch on the ground side from pin 20 on the ECU. When that relay sees ground from the ECU it sends chassis-ground to the pump and turns it on full power. During most conditions though, that relay is off and the pump is grounded directly through the ECU on pin 108 with the varying level stuff. Mostly people have ignored the stock relay and pin 20 altogether (leaving it where it is to maybe do it's thing) and made their own fuel pump circuit with relay switching with the ground reference from pin 108 to give the pump full power the rest of the time. I don't know how you're wiring your swap but cutting pin 20 eliminates the stock relay on-off control that Nissan had in there, which might still work. My uneducated guess would be Nissan added that relay and switching function into the ECU after having problems with the direct grounding through the ECU (during hot starts if I'm reading the FSM right), OR the FSM could be a tiny bit wrong and confusing… Long story short, I don't see how using them together as I marked on the drawing could be a problem; both pins would only be providing a ground reference to switch a relay, but I posted it up because the relay existing at all is strange to me.
JSM: (2011-06-23 16:56:43)
I manipulated the Original 300zx wiring diagram to better show the layout. Pin 108 and Pin 20 have conditional logic. Pin 108 is used at Cold startup and if Pin 20 is cut will always use Pin 108. Pin 20 is used once the car is warmed up. This is when the varrying voltage logic comes into place per the instructions. You might be right be able to connect them together as you show, but I don't think you will not eliminate the varrying voltage because the ECU can perform both test still, cold and hot. It will then automatically varry the voltage.
Addtionally, when you look at the main harness plug from the body, Pin 108 is a very big guage wire, pin 20 is very small guage wire.
Manipulated 300zx wiring harness to show only Fuel Pump:
[archived image: WiringFP300zx.jpg]
The route I'm going to try from another thread:
[archived image: fuelpumpMod.jpg]
JeffSly: (2011-06-23 19:58:33)
14ga. Because Pin 108 sees the full amperage of the pump in stock trim, not through any relay.
Your diagram may work fine I don't know, but it ignores the stock fuel pump relay which, under a few conditions only, may be needed to run the pump full power (and has nothing to do with varying the pump speed!).
JSM: (2011-06-23 23:36:50)
Your're right. I thought one thing and typed it another on the Pin 20. :-? There is no way that it does anything but control the relay. And I understand that pin 108 is what varies the voltage.
Help me undestand why you want both pin 20 and 108 hooked together if they do seperate functions? How would this not confuse the ECU? Also isn't the point of this thead to eliminate the variance of the pump altogether and run at 100% voltage at all times?
You said: "Your diagram may work fine I don't know, but it ignores the stock fuel pump relay which, under a few conditions only, may be needed to run the pump full power (and has nothing to do with varying the pump speed!)."
This is what I wan't! I don't want the voltage varied.
JeffSly: (2011-06-24 01:16:20)
The way I see it they do the same function just at different times. If I cut pin 108 at the ECU in the passenger footwell and splice it into pin 20, then now both of those wires give possible path to ground to switch the relay and run the pump at full voltage. It can get that ground from either pin and the ECU can only see the current draw of the relay coil, so I don't see an issue with them being joined. Either path to ground works. Either pin closes the relay to give full power to the pump, so the pump has full power anytime the ECU would have had the pump on.
The possible problem here is that the existing power wiring is undersized. If it isn't, I see the splice of pin 108 into the wiring from pin 20 at the ECU, leaving that wiring intact, as the easiest way to achieve full voltage all the time.
JSM: (2011-06-24 01:47:07)
I see your logic, however, what will prevent the ECU from regulating the voltage if both pins are connected? Why wouldn't the ECU think both are working and adjust accordingly. Also i'd be curious to how the relay will react to getting two different signals to the same spot.
JeffSly: (2011-06-24 02:28:16)
The ECU alters the ground side resistance to attenuate voltage. With any full voltage mod that uses pin 108 the ECU will still try to vary the resistance, but it will be lowering the voltage of a coil on a relay, not the fuel pump. A relay coil seeing 13.5V or one seeing the lowest of ~9.4V or anything in between is exactly the same - the relay will click, so you get full power through the switch side of the relay, even while the ECU tries to vary the voltage/pump speed. Again back to stock wiring to see if I can settle this for you (and the other parallel thread), the fuel pump always is connected hot side and runs when it gets a reference to ground, yes?. At the fuel pump connector there are three wires/connections: hot, ground, and shield for the ground. That ground wire on the wiring diagram is 108, but goes to pin 108 AND a switched ground on the fuel pump relay switched by pin 20 (you posted up a diagram that shows this). So when you do the mod as originally described here, cutting the wire at the fuel pump connector in the hatch area, you're using that pin 108 wire as the ground reference to switch a relay that the fuel pump is now wired to. BUT that ground reference on that wire can ALSO come via the stock fuel pump relay switched on pin 20. So the diagram from MichaelP that you cleaned up is not showing any of that, but I'm guessing it's there.
The mod usually adds a relay to a circuit that already has a relay it rarely uses. I've suggested the same thing without an extra relay. Either the relay is wired to two paths to ground, or the fuel pump is, shouldn't matter either way.
michaelp: (2011-06-24 03:39:28)
None of this really matters, using the fuel pump ground (which leads to Pin 108) or the relay on/off ground (which leads to Pin 20) will still switch the relay/on off to provide full voltage to the pump. Easiest way is to just use the power/ground going to the pump in the hatch to control the relay, then run a new full voltage power through the relay switched side with a new ground. Gives the pump battery voltage whenever the key is on for less than 5 seconds, or the engine is running…exactly as OE operates it, only full voltage at all times. No reason to complicate crap.
Plus doing it how I said takes away the risk of melting stock wiring with better pumps like many people including myself have had happen.
michaelp: (2011-06-24 03:45:16)
[quote]JeffSly wrote:
Because any pump better than the stock one will cook the old ass OE wiring, but not the 10A fuse…I can't completely argue with this, because I know it's happened, pictures exist etc. Worse my car's nowhere near ready to find out for myself, but the high-flow Walbro's at stock pressure shouldn't exceed 10A by much if anything according to anything I've found ("high-pressure" version: 7.5A @ 13.5V and 40psi flowing 70 gal/hr, for example). Why shouldn't I expect an old ass 14ga wire to stand up to that?
Mine never exceeded 10A. I still run a 10A fuse to this day with my new wiring, I never blew a fuse. I simply overheated the shitty stock wiring.
Easiest way is to put a relay in the rear of the car. Run OE fuel pump + to Relay PIN 85, and OE fuel pump - to Relay PIN 86. Run new power wire from battery (fused up near the battery) to the relay PIN 30, and then relay PIN 87 to the fuel pump +. Run the fuel pump - to a bolt on the body. It'll be full voltage for the first 5 seconds of key on, and whenever the engine is running, just like the OE ECU controls it other than being full voltage 100% of the time.
JeffSly: (2011-06-24 04:21:14)
Well that's that then. Shouldn't be that, but I won't be stubborn about it and expect anything past stock from the stock wiring. 8) Thanks for clearing that up.
I still don't consider NOT adding a new relay, sometimes switched by an existing relay to be complicating crap especially on an engine/ECU swap. For JWS it matters, those two grounds that you talk about using interchangeably (108/20) are switched by the ECU to turn on the pump. I can only guess you need both. It'd be interesting for you or someone with it rewired like you described to pull the stock fuel pump relay and see if it does anything noticeable.
JSM: (2011-06-24 14:57:09)
Oh I see why we differ now. You're assuming I'm using stock wiring which I am not. I'm using the 300zx EFI harness only and associated components where applicable. This is going into my 260z. I needed a place to understand how to hook up the Fuel pump and stublmed across this site. I'm only using pin 108 to control my own wiring harness for the fuel pump I have.
I'm going to use the EFI harness wired in like so to my own realy and fuel pump.
[archived image: WiringFP300zx2.jpg]
JeffSly: (2011-06-24 16:13:31)
That is entirely NOT where we differ my friend. It's where you and everyone else differs. I've assumed you're not using the 300zx body harness the whole time, which is why I'm going back over this yet again. Everything ELSE described here is telling how to modify the stock body harness.
Everyone else (probably) that has done this mod STILL HAS pin 20 connected to the stock relay connected to their fuel pump. It can and does still turn their pump on under the conditions for why it existed in the first place. If you don't connect pin 20 it is pretty much equivalent to removing the fuel pump relay on a stock 300zx and assuming there was no reason for it to ever be there/the conditional logic on pin 20 and 108 are totally redundant and that the ECU could run the pump properly all the time without it. And honestly, it might, it wouldn't be the only Nissan control that is less than needed, I'm just saying you might be the pioneer of deleting it.
JSM: (2011-06-24 17:17:18)
Can EVERYONE else that has done this mode chime in and let us know if you left pin 20 connected?
The way I read this post and viewed MichaelP original drawing he did not use pin 20:
viewtopic.php?f=6&t=28700
Per this swap on Hybridz he did not use pin 20 either:
http://forums.hybridz.org/index.php?showtopic=49087
Now the ECU controls the â power that switches the FPR on thru the ECU pin 108, and the 16 l/r wire is ignition + to the FPR. Now I have no explanation for this part, but according to the book, pin 20 from the Z31 ecu should activate the FPR, which then loops back thru the FPR to pin 108. This did not work for me. However, it worked perfect when I connected the new wire going to pin 108. Again I donât know why pin 108 is working for this and pin 20 did not, but it sure is working well on my car.
Also I disconnected the knock sensor and did not switch any of the injector wire.
It's difficult to argue with the results, however, I understand your point.
JeffSly: (2011-06-24 17:33:56)
No it's not, and no you don't. One last time: the stock 300zx uses pin 108 to run the pump direct from the ECU AND pin 20 to run the pump off the relay at different times/different conditions. When it's using 108 it is NOT using the relay. I never said 108 alone wouldn't "work", just may not work 100% as Nissan drew it up.
JSM: (2011-06-24 18:12:56)
[quote]JeffSly wrote:
It's difficult to argue with the results, however, I understand your point. No it's not, and no you don't. One last time: the stock 300zx uses pin 108 to run the pump direct from the ECU AND
pin 20 to run the pump off the relay at different times/different conditions. When it's using 108 it is NOT using the relay. I never said 108 alone wouldn't "work", just may not work 100% as Nissan drew it up.
I âm content on disagreeing with you on this, yes the results speak for themselves. It works off of pin 108. And again, yes I get it about the pin differences; I'm not sure why youâre so stuck on trying to beat this in my head. I'm NOT USING THE STOCK RELAY!
I care about the performance of how I can use a newer system in an older car. NISSAN never had any intention of me doing this so I could care less if it is how NISSAN designed it, just as long as I can get the benefit of the 300zx ECU and leave a bit of the safety feature from the ECU in place. If it's only 75% and works correctly, I don't care. If all else fails, I'm going to circumvent the ECU controlling the fuel pump altogether.
The entire point of this thread and site is for performance. Performance to me means push it past the stock NISSAN design to get the best results possible, while keeping as many safety and operational functions in place where possible. I'm doing this alone by simply using the newer design, regardless if I get every part working EXACTLY as NISSAN designed it.
I appreciate your time and effort in explaining the full functionality of how this was intended to work.
JeffSly: (2011-06-24 19:06:01)
Kay thanks for your appreciation 8) . In all seriousness, my concern was that with pin 108 only the pump may not come on for the initial 5 seconds or when starting with engine temp above 100 Celcius and such, because the ECU has 2 means to turn the pump on, and you're only going to use 1 of them. Was thinking 20 could be used exclusively under the conditions listed in the FSM and then your car wouldn't start or something.
I agree with your wiring diagram completely and apologize for complicating things. Thanks for helping me understand (I think) why that semi-redundant relay is in my car.
JSM: (2011-06-24 19:09:35)
[quote]JeffSly wrote:
In all seriousness, my concern was that with pin 108 only the pump may not come on for the initial 5 seconds or when starting with engine temp above 100 Celcius and such, because the ECU has 2 means to turn the pump on, and you're only going to use 1 of them. Was thinking 20 could be used exclusively under the conditions listed in the FSM and then your car wouldn't start or something.
Understand completely. Will find out, hopefully not the hard way! :-D
JeffSly: (2011-06-24 19:20:32)
Nah, I now think you'll be all set and that a lot of 300zx owners could free up a blue relay and shed an ounce or two if they wanted. :nanan?re
88sinZ: (2011-11-16 13:39:30)
useful charts for wire gauge determination for thoes running real fuel pumps
[archived image: 4313-1B2WireChart.jpg]
[archived image: IMAG0162.jpg]
rangerkid: (2011-12-15 05:12:35)
My fuel pump runs constantly while the ignition is on, could it be possible that I have a problem in the ECU?
PulseCode: (2012-01-07 00:50:30)
Have we gained any clarity from this 5 page post? Does anyone have the diagram from the OP?
My '87 NA2T conversion running 12 psi. boost, has slowly been running worse and worse. I do hit
boost regularly. Shorted/ open fuel pump circiut is the only code popping up on the ECU. Thanks.
JeffSly: (2012-01-09 19:59:47)
The 5 pages contain mostly useless misunderstandings because there are many ways to wire many fuel pumps, and what Nissan did originally was most likely a work-around.
Personally, yes, it changed my life. What are you wanting to do?
PulseCode: (2012-01-10 01:39:48)
Thank You Jeffsly for your response. I just want my NA2T conversion to run right. Since Code 22
is the only thing popping up on the ECU during diagnostics, I'd like concise info specifically on what/
where to check first for fried wires and a wiring diagram that has reached group concensus for reliability.
Thanks.
JeffSly: (2012-01-10 04:14:40)
I don't know anything in particular about your Code 22, but here's my understanding of things, all of which has been said here or elsewhere, but not always clearly.
With anything drawing more current than the stock pump (in good condition), both the fuel pump connector beneath the carpeting inside the hatch, and (via current discussion in another active thread) the wiring pass-throughs used from the pump itself through the top plate/fuel tank have been suggested as cause for the fried wiring.
So then a few things: With everything stock, you should be able to splice at the ECCS according to a diagram I posted in pg 3 I think to always get full voltage to the pump without changing anything else, relying on the existing fuel pump relay.
BUT, I think the common group concensus involves adding another relay somewhere in the hatch area like so
[archived image: fuelpumpcontrolblue-1.jpg].
Here the stock fuel pump relay is ignored, and you tap into the hot wire to the fuel pump in the hatch area, and cut the pin 108 wire from the ECCS to switch the new relay, and provide a convenient local ground to the fuel pump on the switched side. If the wire is suspect, a new +12V source wire needs to be run in place of the old one, but the ground from the relay is short/convenient. Can't go too wrong with 10ga. for those.
PulseCode: (2012-01-10 15:38:41)
Thanks, Jeffsly for the clarification. Though the diagram on page 4 posted by JSM
appears to be 90 degrees turned, It looks identical to the one you just posted, correct?
JeffSly: (2012-01-10 17:33:03)
Functionally speaking, yes, but actually no. That diagram shows the relay controlling the pump by switching the +12V side, while mine shows controlling it by switching the path to ground on/off the way Nissan wired it. But if you're completely rewiring the pump, as long as the relay coil ground is from ECCS pin 108, either way should work. So why actually no then?
Stock pump was wired to have +12V connected to the pump always, then ECCS pin 108 could provide the ground to turn it on, or ECCS pin 20 could provide ground through the stock fuel pump relay (passenger side B-pillar) to turn it on. What I drew most recently maintains that stock relay (although I didn't show it) and its ability to turn the pump on whenever pin 20 is telling it to. All indications are this doesn't matter, but I think most people who have added the relay for full power have done so by controlling the ground side, leaving the stock pump relay in place to do its thing. So then the crappy version of the full diagram would be like this, where the new relay is wired just like the existing one is.
[archived image: fuelpumpcontrolfull.jpg]
G-E: (2012-04-11 18:09:03)
[quote]JeffSly wrote:
Thanks, Jeffsly for the clarification. Though the diagram on page 4 posted by JSM
appears to be 90 degrees turned, It looks identical to the one you just posted, correct? Functionally speaking, yes, but actually no. That diagram shows the relay controlling the pump by switching the +12V side, while mine shows controlling it by switching the path to ground on/off the way Nissan wired it. But if you're completely rewiring the pump, as long as the relay coil ground is from ECCS pin 108, either way should work. So why actually no then?
Stock pump was wired to have +12V connected to the pump always, then ECCS pin 108 could provide the ground to turn it on, or ECCS pin 20 could provide ground through the stock fuel pump relay (passenger side B-pillar) to turn it on. What I drew most recently maintains that stock relay (although I didn't show it) and its ability to turn the pump on whenever pin 20 is telling it to. All indications are this doesn't matter, but I think most people who have added the relay for full power have done so by controlling the ground side, leaving the stock pump relay in place to do its thing. So then the crappy version of the full diagram would be like this, where the new relay is wired just like the existing one is.
[archived image: fuelpumpcontrolfull.jpg]
to be foolproof as other people pointed out bridge 20 with 108 but otherwise looks good [archived image: smile.png]
JeffSly: (2012-04-11 20:21:43)
- lol: As you pointed out in 2006 I believe. Just a whole lot of clutter here since.
G-E: (2012-04-11 23:48:42)
[quote]JeffSly wrote:
to be foolproof as other people pointed out bridge 20 with 108 but otherwise looks good [archived image: smile.png]:lol: As you pointed out in 2006 I believe. Just a whole lot of clutter here since.
yea I am amazed how many threads there are here that haven't progressed any while I was gone… or it's like reading that last page eureka moment that someone had already :P
stufferton: (2012-05-20 08:59:02)
Re:
Correct me if I am wrong, the original image you had posted with this comment is no longer showing, but this is what you meant correct? It seems far simpler than going through and wiring in a new relay, if my understanding is correct here.
G-E: (2012-05-20 10:00:32)
Re: Re:
[quote]stufferton wrote:
take the hot side and connect it to the relay's coil hot and switched hot directly, then run the switched ground to the pump hot and the coil ground to the ecu.
Correct me if I am wrong, the original image you had posted with this comment is no longer showing, but this is what you meant correct? It seems far simpler than going through and wiring in a new relay, if my understanding is correct here.
Yarp…
Careless: (2012-06-03 06:06:29)
ok. so now that I wired in a nice and healthy 10ga wire from the front with a 15 amp litefuse right next to the battery, I'm going to drill a tiny hole in the waterproof fuse holder and skim the top with some hard resin so that it forms a clear window so that I can see if the fuse is blown without pulling it from its nested location.
But now I have a situation with the blue connector that has the Black and Blue/White wire. It seems as though they are both grounds or something? For some reason I can't get my relay coil to trigger by wiring each side into those wires. But one of them should be supplying power, no? To feed the pump? Instead, if i put my circuit tester to the power wire, and probe the black wire on the 5 second prime when flipping the key over, the circuit tester starts to moan/creek (its audible and visual). So that would indicate the black wire is the ECU ground phasing wire, right?
So doesn't that leave the blue as the power wire? Since it also seems to feed power to the sending unit control box? It doesn't seem to trip the circuit tester when connecting to ground and probing the blue power wire.
[archived image: jUqpB.png]
why blue no has 12v? pump worked before. I'm asking because the 10ga power wire I ran is too purdy to cut back and tap into. I don't want to start making splice connections when I does not has to.
EDIT: OEM fuel pump 12v blue/white wire works better when fuel pump fuse is actually IN the fuse box. I removed it to test my turbo timer countdown, and didn't put it back in after everything was all done. Pump is nice and pumpy now.
MY1PATH: (2012-07-04 21:44:51)
I did something similar with my m30 ecu. The variable voltage wire never goes below 9v and Nissan standard relays only need 9v to function. (maybe a little more when they are cold)
I spliced the variable wire with the other ecu wire for the relay to help it pull the relay open on cold start ups (when the relay may be a little stubborn for 9v) and then ran the splice to the relay.
Fuel Fuse>>> Relay Coil>>> variable (104) spliced with relay trigger (18)
Fuel Fuse>>> Relay Closed>>> Fuel Pump>>> Ground
[archived image: fullpowerfuelpump.jpg]
It looks exactly just like the picture stufferton posted except for the M30 uses pins 104 and 18.
I have a Fuel Pressure Guage on and before the mod I noticed that even if I pinched the return line my idle pressure barely stayed above 30PSI. This is what made me want to do the mod because I was concerned about it not being able to keep up at idle once I go to a 3.3 block and or e85. since it only provided JUST ENOUGH and Nothing more on a gasoline 3.0.
After the relay mod my idle pressure was 36 and if I pinched the return line it would climb like it should.
green300zx: (2012-07-13 16:24:17)
i know this sounds stupid but i can do all the wiring no problem but when it comes to knowing like what a relay looks like or what relay your talking bout so many different things run across my mind on what it actually is but the stupid part is would help alot if you had a photo maybe of the relay for people like me who dont know what it looks like. but thank you so much for taking to write out how to do this so informative im just lost on what the relay looks like.
85NA2T: (2012-07-13 16:27:58)
..........
Jared86NA: (2013-04-14 08:51:57)
I know this thread is really old, but it took me far too long today to figure out how to wire my pump. Yellow wire from Pin 20 (only!) to blue fuel pump relay coil negative. New wire +12V from battery to both blue relay coil positive and relay switch positive. New wire from relay switch negative to fuel pump positive (blue/white wire on car-side of fuel pump harness connector). New wire from fuel pump negative to body ground. Third wire on pump not used.
Initially had Pins 108 and 20 to the coil negative, but this caused my pump to run whenever the battery was connected. It had been a long evening at this point and I suppose it's possible I had the wrong wire. With only wire 20 powering the coil, the fuel pump primes 5 sec, shuts off, and runs when the engine runs. Went for a test drive from stone cold to running temp and the pump worked as it should. Hope this helps someone.
TurboZcaR: (2013-04-19 19:06:45)
So what is the correct way to do it.. I just read through all 6 pages and now I'm confused…
BackRoadED6: (2013-05-01 01:58:37)
Agreed ive done this mod on dsm's but it more or less involved running a fused 10ga wire from the battery to the fuse and then from the fuse to the power side of the pump and using the original pump power supply to switch the relay. Do you have to worry about hurting the system when you splice 108 and 20 together? and do you need to run a fused wire direct from the battery or not? It seems some people are and others aren't. Understand the concept but everyone seems to be disagreeing so much.
Shuman47: (2013-06-10 03:53:00)
From what I gathered from this, you can simply use the current fuel pump power and ground wires as the relay control circuit, then run a separate power and ground from the battery to the pump through the relay load circuit to provide the constant 12v feed. No need to mess with the ECU or the existing fuel pump relay. Could be wrong though, I'm going to try it that way when I get home from vacation.
ajaxism: (2013-09-25 11:46:37)
My fuel pump is a lot louder now after this mod.
I presume this is normal as it's working as hard as it can at all times.
NuCOTech: (2013-10-09 20:09:50)
I know a lot of people have been asking for a diagram/picture to help them do this mod. I know it would have helped me because I went through this thread a few times and tried multiple ways on how to wire this thing up before I finally got it right. So there are some suggestions in here that do not work or make the pump run with the ignition off. So here is a picture and what I did to make this work.
http://i154.photobucket.com/albums/s…ps93b30527.jpg
Red wire - Terminal 85 - Pump +
Black wire - Terminal 30 - Body -
White wire - Terminal 86 - From ECCS -
Green wire - Terminal 87 - To fuel pump -
Terminal 87a is not used.
Hope this helps.
wbnethery3: (2015-08-07 04:18:04)
Question on this confusing thread
I realize this is an old thread, but doesn't look anyone's been here in a couple years. My question involves the need to run a new dedicated relay, hot wire and/or ground wire for the pump.
Since there is already a dedicated ground when the prime signal (pin 20) activates the relay, won't the same ground be sufficient for normal operation? I see others appear to be running new hot wires through the relay (as shown by MY1PATH) or a new dedicated relay and hot/ground wires (as shown by JeffSly).
My FSM diagram for the fuel power circuit is essentially the same as shown in the post by Careless… but a little less detailed (different year FSM I assume). I've drawn a diagram of what I'm proposing should work, but I need to know if this will be a problem. The connection from the fuel pump to pin 108 is cut, and pin 108 and pin 20 are jumpered. This should always give the coil a path to ground.
[archived image: Fuel-pump-wiring-mod.jpg]
The diagram is part of a section that describes the operation of the pump, and I'm a little concerned that the relay will now be energized 100% of the time. Will this cause the coil to burn out? It looks like the relay is normally only powered for about 30 seconds after the engine starts. Don't see the need to trigger a second separate relay unless one relay can't handle the amps for a sustained duration, or if the dedicated ground used for priming is under-sized for full operational amps.
[archived image: fuel-pump-control-description.jpg]
Has anyone done it the way I've shown, without a second relay?
Bremsen: (2015-12-14 15:09:27)
I'm going to bump this because I just want to know if the ECU needs to see the fuel pump at all? I'm thinking about simply wiring the fuel pump to a toggle (because race car).
wbnethery3: (2015-12-15 05:10:21)
ECU is blind to what that ground wire does… no feedback from the pump. Believe original intent was to vary voltage to the pump, but the direct-feed arrangement shown above eliminates that. The ECU has relatively few inputs… air flow, crank angle, CHT being among the more useful. I suspect you'd be fine just direct power to the fuel pump… as long as you remember to flip that toggle off when you finish racing…
Bremsen: (2015-12-15 15:35:34)
Cool, that's what I figured, but wanted to see if anyone knew for certain. Thanks for the reply!
After I posted I was looking at the diagram and thought if it did need to see it, I could leave the relay in place and just hard wire the pump. The ECU would still activate the relay, but it wouldn't do anything. But I'm for simplicity and if its not needed it gets pulled, wiring and all.
Whole car is controlled by the master kill, and even if I forget to turn it off I'm pretty sure the external pump will be loud enough so that forgetting it will be unlikely, lol.