Fuel Pump Modification

The following is a mod I did that really works good. I could feel an improved performance. Has anyone else done this. I got some information from the Z31-Performance web site. I change the diagram  and added an extra SSR (Solid State Relay) instead of a regular auto relay. The SSR is much more reliable than the Standard Auto Relay. Of course it also cost a lot more than the relay, about $100 bucks for one SSR. You can just use a Automotive Relay 30 Amps. Let me know what you guys think.

ECU pin 108 controls the fuel pump  during normal operation. No Relay used during normal operation. The fuel pump relay is only used when there is fault in the fuel pump circuit or if more gas is called for. The fault mode allows the fuel pump to operate until the power is shut off.  ECU pin 20 turns the Relay on in fault mode.  See service
Manual page EF – EC 26. Also see EF & EC31 for faults.  "If fuel pump circuit is malfunctioning, fuel pump relay comes "ON" until the engine stops. This results in fuel pump getting power from the fuel pump relay.

Remember use caution when working with gas, no sparks, open flame, smoking, etc.

Here are some pictures of the install.
https://www.dropbox.com/sh/n59xhg2smqpil1y/a0mJlBrWmV/Fuel%20Pump

[img<a href="https://www.circuitlab.com/circuit/4u9844/fuel-pump-control/"><img src="https://www.circuitlab.com/circuit/4u9844/screenshot/540x405/"/></a>][/img]

On the Z31 performance web pages they tied ECU pin 108 and pin 20 together and then connected to the SSR.

Calvin just curious but what performance is supposed to happen? i can understand that you are giving the fuel pump power till the engine is off and so it wont kill the engine if there is a code yet where are the benefits to be had? sorry i just dont understand.  i have the ca18 so maybe mine doesnt have the fault mode? thanks in advance

Jeremy

The way Nissan turns the fuel pump on is by a 20 hertz waveform of varying time on and off as well as changing the voltage level (ECU pin 108).  So with this mod you do away with the 20 hertz waveform and voltage swing, instead you are supplying the fuel pump with the constant 12 VDC. Thats why you ground out one side of the fuel pump and apply 12 volts to the other side thru the SSR. I used pin 108 to turn my SSR on. This allow for maximum fuel flow to the injectors.  Also I added a external pressure regulator which I have adjusted to around 40 psi. Any fuel not used is returned to the fuel tank. I mean I really felt the difference, also the rough idle went away. Time will tell if the fuel pump will fail with being on constantly but I don't think there will be any problem as the pump is made to turn fully by activating the original relay, which give more fuel when called for, thru pin 20.  At least thats the way I see the fuel pump working.

ok very cool thank you i didnt know that it used a waveform i knew about the varying voltage and so that it why i used an accuvolt being triggered from the fuel pump ground output and made it supply a constant 14.4 volts anytime the key is turned on, so it sounds like we did about the same just different ways.

Sick, I think I am going to try this out tomorrow and see how it works on my car. I noticed my car has a pulsing feel at WOT sometimes and have been picking my brain to figure it out (Not always consistence and can't replicate the problem hahah) and this sounds like the key to my problems

..I did this a little over a year ago and no problems at all...i could tell the differance for the better as well.

so it's basically a refined form of hardwiring your fuel pump to constant 12 volt ghetto style but it's with a relay. sounds pointless to me. nissan designed it to work so i'd take an engineers standpoint on wiring and circuitry. Without the wavelength it keeps the pump on constantly and that just shortens fuel pump life. probably only has nominal gains of like 0.00001% anyways. you don't need full fuel flow at idle.

I'm going to guess that any gains are placebo, until I see a dyno run before and after with the solid state relay being the only change.  the fuel pressure regulator keeps the rail at the proper pressure, if you do notice a gain from this mod, it's probably because your regulator was/is bad.

I don't know what to tell you guys, like I said I really did notice an improvement and also I do have a standalone fuel regulator. So the regulator was not bad so I can rule that out. The regulator was installed first prior to the SSR on the fuel pump.  I'm just trying to share what I did, your free to do what you want. I don't have access to a Dyno, Sorry about that.

If you read the service manual it states "The fuel pump is controlled by the E.C.C.S control unit by adjusting the output voltage supplied to the fuel pump. " Page EF & EC -26. So I read this as if you increase the voltage to the fuel pump you increase fuel pressure.  Correct. That's why I noticed a diffidence after this mod. Am I reading this correctly?

silverton on 02:16:49 PM / 12-Nov-12I'm going to guess that any gains are placebo, until I see a dyno run before and after with the solid state relay being the only change.  the fuel pressure regulator keeps the rail at the proper pressure, if you do notice a gain from this mod, it's probably because your regulator was/is bad.

Actually I got the SSR out of an old piece on electronic equipment so the price was right (Free). Also I wanted to use an SSR as the contacts won't degrade as a Relay will. The SSR is just an electronic switch that's why I used it.  Why do you say the SSR is over kill. It is working great. If you look at the schematic of the circuit. You'll see it  is working like I wired it. Instead of the ECU controlling the ground I just tied the one leg of the pump to ground and used pin 108 to turn on the SSR.  I ran the 12 volt line directly from the battery with 10 awg. wiring. Also if you look at the Z31 performace you see a lot of people have done this mod. and see that it does work. Give it a try and see. If you need more info see the link below from Z31performance.

http://www.z31performance.com/forum/viewtopic.php?f=6&t=282&hilit=full+voltage+wiring+mod

nismo_200sx on 01:53:29 PM / 12-Nov-12so it's basically a refined form of hardwiring your fuel pump to constant 12 volt ghetto style but it's with a relay. sounds pointless to me. nissan designed it to work so i'd take an engineers standpoint on wiring and circuitry. Without the wavelength it keeps the pump on constantly and that just shortens fuel pump life. probably only has nominal gains of like 0.00001% anyways. you don't need full fuel flow at idle.

silverton on 02:16:49 PM / 12-Nov-12I'm going to guess that any gains are placebo, until I see a dyno run before and after with the solid state relay being the only change.  the fuel pressure regulator keeps the rail at the proper pressure, if you do notice a gain from this mod, it's probably because your regulator was/is bad.