Did High Fuel Pressure, Or E85, Kill My Rb25det Stock Injectors?

[scotty nm35]

Yea but have you fitted a mechanical Fuel pressure guage and looked at the pressure in those cases where you have a 460L walbro on the stock reg. I would be shocked if it was at 35ish psi it should be.

When you say you can supply an aftermarket reg, I'm a little confused, whats the difference between getting them from you and from ebay or nengun for example?

Yes, most guys don't want pressure gauges fitted, it doesn't look too stock. I have a temporary gauge I use for most pump/injector installs. It's the last thing I setup before heading to the tuners.

The Evo7 I rebuilt had a similar issue, it ran 65psi base due to having a 1.5mm restrictor in the fuel tank. I drilled the restrictor to 4mm and was able to drop the pressure to 35psi at idle, that was with a Walbro 460L pump capable of 800hp flow on 98. If you are seeing similar pressures you have a very small restrictor (1mm) somewhere in the return line, either the reg or something downstream of it. Some Nissans have a restrictor in the hose off the reg for some reason, usually banded with white.

Local warranty isn't an issue until something goes wrong, and you really don't want something to go wrong with a fuel system. Sending a pump or injector back overseas for warranty is a waste of time when you can replace it for not much more than the shipping. Plus the Aus dollar is so crap these days, most parts are cheaper locally if you know where to look.

The amount of knockoff regs getting around is a joke, just have a search for knockoff Sard regs and see how good they are at making them look the same these days. Fuel pumps are in the same boat. If you are happy running Ebay gear knowing it hasn't been rigorously tested, or perhaps doesn't work at all, I take my hat off to you, no way I would trust knockoff fuel system components... Even the legit ones have caused me grief in some situations.

Hope that helps. PM me if you need more information.

[sonicz]

Thankyou for the help guys. I think I've now personally realized in my situation I either fit my Nismo FPR and see what happens or go back to stock pump, I just have been admittedly too busy/lazy to do the work.

That said you guys have made me realize that no matter what I do to normalize the pressure, I will never be able to reduce the amount of fuel being pumped around unless I change the pump. I also think that unless you get an aftermarket ECU, the stock pump it also most ideal as even if you get the fuel pressure bang on, the flow characteristics of the stock pump are different to an aftermarket pump especially when taking into account the fuel pump voltage control system skylines have.

With ref to your first question: yes, there's no good reason to be pumping huge amounts of fuel around if you don't need to. It certainly leads to hot fuel in the tank, which doesn't help anything. I just assumed that you had your pump, wanted to keep it and wanted to know how to make the rest of the system work with it.

With ref to pulling the hose off the regulator.....if the reg is fully open and not able to control the pressure against the full flow of the pump at idle with the vacuum hose on, and the pressure does not change when you pull the hose off, then it really just shows how far too small the reg actually is. There's actually two possibilities here though. 1) it is working (not broken) but is simply too small. 2) It is broken and jammed at a certain (small) opening. Hard to tell which, even with the test you've done.

With respect to your question to Scotty about what the difference is between buying from him and buying from some web vendor, the difference is that you talk to an actual person who has a brain and works on these systems all the time and might be able to fault find your problem before you actually buy something (off the net) that proves to not solve the problem because the problem was actually something else. Plus, when it comes to choosing the right reg (assuming that buying one turns out to be the right thing to do) you will get solid advice as to which ones are good and which ones are not. If ou just go buy a Sard or whatever from Nengun, you are somewhat on your own. Whether that is important to you or not is up to you and your experience/knowledge/research levels.

Let me just get this straight, when the reg is fully open, it lowers the fuel pressure of the entire system because there is a bigger opening for the fuel to travel through, thus less fuel is backed up meaning easier flow meaning lower pressure? With this in mind, even if a Aftermarket FPR is able to set a base pressure of 43 PSI, I will still be pumping an absurd amount of fuel around and an FPR will do nothing to change this?

And this is with a Chinese copy pump.

Honestly who needs this much fuel to be flowing around, even if you are making 2000hp? The amount of fuel that comes out of the hose when I was emptying the tank was just absurd. It honestly would only take a minute or two tops to empty an entire 60L fuel tank. What kind of tune would necessitate that much fuel being pumped around....?

[sonicz]

Scotty, with ref to that restrictor in the hose you speak of, have you ever seen it in a 1998 Skyline GTS-T?

I am aware of the knockoffs. The only FPR I have purchased is a Genuine Nismo FPR from Japan, and thats the one I will probably pull of my unregistered Skyline to fit to my Stock (now) daily driver. Though I would probably be interested in a easy to fit onto stock RB25 layout FPR, with a high range of adjust-ability that has a Fuel pressure gauge built into it.

And Lastly, in order to wrap up this fuel pressure setting topic, I need to know these few things.

-Is there any possible damage to the stock injectors, having to open and close in a such a high pressure environment for so long (65psi 2+ years)?

-When I aim to set what seems to be global value for base fuel pressure on a RB25DET of 43PS with the vacuum hose to FPR disconnected, who is this according to, Nissan or tuners? And Is that with the infamous ECU controlled fuel pump voltage regulator Skylines have switched to the Low or High setting (0 or 1 on consult)?

What I mean by this, is that I have done the voltage control mod by earthing out the grey wire in the boot as pictured below and this is how I have been driving the car for 2 years.

This means the pump gets full voltage all the time instead of being dropped down by the ECU at idle. A few days ago I connected the earthed wire back into the wiring loom, i,e as the car comes stock, and the PSI reading on the gauge I fitted now dropped to around 37PSI at the low voltage idle setting. As soon as the throttle is touched, it rises back to to 65psi.

This is what I mean by the stock Fuel pump probably has a different flow characteristics at the two voltages than an aftermarket pump, and I imagine the range of PSI drop is not as great as between 37 and 65 PSI. So no matter what you do as far as a fuel reg is concerned, you can never match the Fuel pressure according to what the ECU expects, IF the stock ECU expects the voltage to drop, and it should as its the one doing it, does it also expect the fuel pressure to drop and takes that into its tune?

This obviously introduces some more complications. Do I?

-Stock reg, stock pump, stock wiring

-Stock pump, stock reg, Earth mod wiring

-Stock pump, Aftermarket reg, Earth mod wiring

-Aftermarket pump, Aftermarket reg, Stock wiring

-Aftermarket pump, Aftermarket reg, Earth mod wiring.

EDIT: I just had a think outside the box possible simple solution to this issue. What would I need to do in order to make the fuel pump work permanently at the LOWER voltage setting, All the time? This would get me bang on the fuel pressure I need and would require no mucking around aside form maybe adding a resistor somewhere?

Edited April 11, 2015 by sonicz

[GTSBoy]

Let me just get this straight, when the reg is fully open, it lowers the fuel pressure of the entire system because there is a bigger opening for the fuel to travel through, thus less fuel is backed up meaning easier flow meaning lower pressure? With this in mind, even if a Aftermarket FPR is able to set a base pressure of 43 PSI, I will still be pumping an absurd amount of fuel around and an FPR will do nothing to change this?

And this is with a Chinese copy pump.

Honestly who needs this much fuel to be flowing around, even if you are making 2000hp? The amount of fuel that comes out of the hose when I was emptying the tank was just absurd. It honestly would only take a minute or two tops to empty an entire 60L fuel tank. What kind of tune would necessitate that much fuel being pumped around....?

Yup, exactly. These days, with massive fuel pumps in use, the smart money is on proper fuel pump controllers to speed them up and slow them down as required.

EDIT: I just had a think outside the box possible simple solution to this issue. What would I need to do in order to make the fuel pump work permanently at the LOWER voltage setting, All the time? This would get me bang on the fuel pressure I need and would require no mucking around aside form maybe adding a resistor somewhere?

This could work. Wouldn't work with the stocker of course - too little fuel. But it might help the massive pump. Might also still not be enough of a fix. Depends on what's wrong with the reg.

[sonicz]

Yup, exactly. These days, with massive fuel pumps in use, the smart money is on proper fuel pump controllers to speed them up and slow them down as required.

This could work. Wouldn't work with the stocker of course - too little fuel. But it might help the massive pump. Might also still not be enough of a fix. Depends on what's wrong with the reg.

So why hasn't anyone done this with a skyline? All you would need is some kind of way to control a variable resistor with a knob. The stock car does this already with the 0 and 1 fuel pump voltage states you would just need to tap into this in a variable way.

Actually making my car run on the low voltage setting permanently could be perfect for a "fix". There could be nothing it all that's wrong with the reg, as you said it may just be a case of it being too little to regulate the massive flow.

I just went out and looked at the fuel pressure after I returned the wiring to stock. Its 37ish PSI with the vacuum hose connected and 43.5ish with it disconnected. God himself could not dial it any better, and this is just dumb luck it turned out this way when the voltage is on the "low" state.

What remains to be answered is,

-Does a stock car have a value of 43PSI with the FPR vacuum disconnected on the LOW or HIGH voltage state? Anyone that has run a pressure test on an otherwise fully stock skyline I would love to know the readings.

-If I permanently set the voltage to run on the LOW setting in order to achieve 43 psi base reading, will this trick the computer in "tuning" itself up to expect a voltage rise under throttle, but not get it, and this lean out and detonate under hard acceleration?

-How do I get the fuel pump to run on the LOW voltage state permanetly??

These are important question I cant believe there is not more information about this.

One last thing for the keen eyed. Some years ago there was debate here on SAU whether the fuel volage earth mod pictured in this thread only allowed the car to run on the high volatge setting all the time, or whether it did that in ADDITION to providing extra voltage to the pump as well. Some said it raised the total volatge of the pump and some said it did not do that and simply stopped the volatge from dropping. Well you can see in the video that my HIGH volatge PSI dropped to around 55 psi, down from 65ish when the grey wire is earthed out. This proves earthing out the grey wire in the boot and ONLY doing this raises the total voltage provided to the pump as well.

New back to stock wiring. Dropped my High volatge state PSI to around 55psi, down from 65psi. You can see I have used hot swappable crimps that will alow me to switch between the wiring methods.

Stock wiring FPG readings

Edited April 12, 2015 by sonicz

[scotty nm35]

Stock the pump doesn't outflow whatever restriction you have, so low or high voltage the pressure will remain at 43psi base.

Larger aftermarket pumps require more current, which the stock wiring can't supply. You should really have fitted thicker wiring through a fuse and relay when you installed it.

If you want to slow down an aftermarket fuel pump you will need a PWM controller preferably, the stock two voltage dropping circuit isn't going to handle the current.

[sonicz]

So you are saying that if you were to hook up a fuel pressure gauge to a completely stock skyline, the pressure would remain at 43 psi whether the pump was on the low or high volatge state, because the fuel pressure regulator would be able to do its job due to the less powefull pump, and the only difference being on the high voltage state more fuel would be circulating around giving more headroom for a better chance of preventing any pressure drop to to usage by the injectors as you are driving instead of idling. Ok makes sense, I did not think about it that way. Damn this lazyness I almost want to fit a stock pump back in just to test that.

Not sure about other larger aftermarket pumps, but the one I have fitted certainly seems to be doing fine with the stock wiring. I saw the threads on the fuel pump wire up with its own fuse and direct feed to the battery those years ago, I honestly thought it complete unnecessary for my application back then, and looking at the fuel pressure now I think I made the right decision to keep stock wiring as the last thing I need is even more power and more fuel to be pumped around. The aftermarket pump even on the completely stock wiring is too powerful, and I would say that when you earth out the grey wire and keep everything else stock, there will be little difference between that and doing a complete rewire through its own fuse and relay.

What do you mean the two stage stock voltage dropping circuit isn't going to handle the current? Its currently switching between the two states fine, and I would not want to raise the voltage any more than what the hi settings already is giving it, in fact I need to drop it.

Am I missing something here, if nothing has burned out yet why would the stock wiring not be sufficient? I have the exact same style pump on 2 two skylines spanning over 5 years of combined usage without wiring problems.

Edited April 12, 2015 by sonicz

[GTSBoy]

The sum of the above post and various previous posts is starting to make me think that your Chinacopy pump is not some super powerful mega fire truck pump. If it were, it would have destroyed your wiring. If it is not pulling massive current, then it is probably not pumping mucho fuel, therefore it is probably that your reg is rooted, rather than any other explanation.

[sonicz]

lol that sounds like there is a lot of guesstimating involved. Your wiring is not rooted so it must not be pumping much? So I guess we are full circle back to FPR. Ok, I'll fit the Nismo FPR and see how I go.

That said I still want to know, do I set the base pressure with the voltage regulator to the high or low position?? OR Are are u guys saying because my wiring hasn't melted (meaning it cant be flowing much more than a stock) that once I fit a new FPR assuming its not rooted, my fuel pressure will be 43 PSI regardless of whether the voltage switch is running on high or low? I still find that hard to believe.

Its probably worthwhile mentioning that once I fitted the new pump, I noticed a MASSIVE increase to how hot my boot gets, and how much quicker fuel squirts out the hose when the pump is primed. Also don't quote me on the exact figure but the guy I got it of said the pumps are used on some motorsport GTRs and it can support up to 800HP. The only reason I got it is because it was something like $90, and stated as direct replacement for stock pump, and all the info I read seemed to say the FPR will keep the pressure in check, so I figured I'm just future proofing and/or having tons of headroom.

I'll let you guys know how the nismo FPR does when I get around to it.

Edited April 12, 2015 by sonicz

[GTSBoy]

That said I still want to know, do I set the base pressure with the voltage regulator to the high or low position?? OR Are are u guys saying because my wiring hasn't melted (meaning it cant be flowing much more than a stock) that once I fit a new FPR assuming its not rooted, my fuel pressure will be 43 PSI regardless of whether the voltage switch is running on high or low? I still find that hard to believe.

That is exactly what has been said a few times now. Even a stock FPR should be able to bypass the full amount of fuel on 13.8V from a much bigger pump than the stocker. So the hi or lo setting on the pump controller shouldn't make any difference to the 43 psi base pressure if the reg is working right.

By "bigger pump" I'm talking plenty of people with Bosch 040s, 044s etc, and the various larger Walbros.

Let me stress to you that nearly every stock Skyline fuel pump, once it had been in service for its life in Japan and then a few years here in Aust was probably at least 50% stuffed. They all struggle to keep the fuel pressure up once the engine is on boost at high revs. That's just about the only thing that keeps them from dropping to 9:1 AFR. As soon as you put a new stocker in (assuming you'd be prepared to spend more on a stocker than a better aftermarket pump would cost) then the amount of fuel going around increases heaps. If you put in a big Bosch or Walbro etc then it goes up even more. So your observation of your boot heating up is no indication that your pump is a monster. It just shows that it's not a flogged out 20 year old stocker.

[sonicz]

Ok, I can see that making sense. The Nismo FPR I have is only a year or so old and it got it brand new so should be in good working order.

In the meantime, I found this interesting and I wonder if you care to speculate as to what is going on here.

Now that I have been driving the car with the stock wiring setup i..e no grey wire earthed to chassis, I have noticed the idle is much smoother, and engine feels a lot smoother too but down on power. Starting up the car takes a lot less to get to 650rpm idle, whereas before it struggled to get it that low. I can almost guarantee you the car is running much richer now than it used to. When I stop after accelerating and the wind wafts, I smell much richer fuel coming out the exhaust. My fuel economy is much worse. Funnily it seems that with the earth wire greyed out, running at a constant 65psi, the car somehow ran a lot leaner, provided more power, now with the wiring back to stock, i.e switching between 55ish psi on high and 37psi on low The stock ECU is running the car much richer up top.

[GTSBoy]

Dunno. Doesn't make sense. Re-earth the wire and see what happens. With all the dicking around you might have changed something else.

[fatz]

If it's not the e85 blocking you injectors

Check you return hose to the tank it will be kinked and causing you high pressure

Easy to do when f**king around with in tank pumps

Very unusual for a fpr to f**k out especially stock

[colourclassic]

Sort of related:

When replacing a stock fuel pump (R33 GTR 195l/ph) with a higher flowing one (Walbro 255/460), is a retune needed? Obviously a larger volume of fuel will be flowing around, but the FPR should theoretically keep the rail pressure the same (assuming the stock pump was working correctly).

That is with an aftermarket computer (PowerFC).

[scotty nm35]

Should make no difference to the tune if the pressure remains the same.

[sonicz]

Sort of related:

When replacing a stock fuel pump (R33 GTR 195l/ph) with a higher flowing one (Walbro 255/460), is a retune needed? Obviously a larger volume of fuel will be flowing around, but the FPR should theoretically keep the rail pressure the same (assuming the stock pump was working correctly).

That is with an aftermarket computer (PowerFC).

Don't make the same mistake I did. Fit a Fuel pressure gauge before you do the swap, get a good check of the fuel pressures and then compare it to after. Only way to know.

[scotty nm35]

You would need to check the pressure at full boost also, it's more important than what's going on at idle.

Countless people have changed fuel pumps without checking fuel pressure. Most have absolutely no problems. It's usually only the large pumps (460L) that have caused issues.