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Removing the Fuel Pressure Regulator


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12 replies to this topic

#1 Myxalplyx

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Posted 10 February 2005 - 09:13 PM

Simple fact of the matter is, I don't know how. All I see are a bunch of vacuum hoses, some screws/bolts and hard lines. I remove this one main bolt on top of the fpr but besides that, it won't budge. I can see the manifold vacuum hose, fuel inlet (from fuel filter, which hard wires through the top of the fpr) and the fuel return. I just can't seem to remove the fpr itself. Can someone offer the newbie some advice on doing this? Thanks!

I hate you!
Posted Image Posted Image



I removed this at first thinking it was the fpr. Oops! Looks like it's some type of recirculation from maybe the exhaust port or something. I dunno! The hard pipe on it went down and under the car. I didn't bother to see where. I'm just going to hook it back up once I figure out this fpr removal thing.
Posted Image

#2 Do It Sidewayz

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Posted 10 February 2005 - 09:30 PM

that's the EGR you took off.

out of curiousity...Why are you taking off the FPR???

if you have an aftermarket FPR...you leave the stock one in place, and run the aftermarket rising rate in series after the stock one.


If your installing a Rising rate just make a nice bracket for it, and mount it to the firewall. Go get some Fuel Injection hose, and run from the return hard line on the engine, to the Rising Rate. Then from the Rising Rate to the hard line which leads back to the tank (this is located behind the strut tower).

There's no point to taking off the Stock FPR unless it's knackered (very unlikely) or unless you are trying to modify it to increase base fuel pressure.

#3 Myxalplyx

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Posted 11 February 2005 - 10:08 AM

[quote name='Do It Sidewayz']that's the EGR you took off.

out of curiousity...Why are you taking off the FPR???

if you have an aftermarket FPR...you leave the stock one in place, and run the aftermarket rising rate in series after the stock one.[/QUOTE]

This is the reason why. I had previously asked this in another thread:
[quote name='Myxalplyx']

Can someone tell me if this would work on an EA82T?

http://cgi.ebay.com/...sspagename=WDVW

Posted Image


If I can use this, is this to be put in upstream (before), downstream (after) or in place of the stock fuel pressure regulator.[/QUOTE]


And the reply was this:

[quote name='RavenTBK']The answer is "C", in place of. Adjust the base rate to match the stock regulator, and run. We use rising rate regulators on our turbo Datsun ZXs.. common swap with okay results.[/QUOTE]

From this thread:
http://www.ultimates...?t=30186&page=1



No-one else said anything different so I took it that I needed to remove the stock FPR and put the rising rate on in place of it.

#4 Do It Sidewayz

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Posted 11 February 2005 - 11:01 AM

the correct answer would have been B.....Downstream

the stock FPR can still open up and try to bleed pressure all it wants..but the RRFPR which is downstream of the stock FPR will still raise the fuel pressure.

You can just replace the stock one...but there is no point.

#5 Skip

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Posted 11 February 2005 - 11:25 AM

Okay both are correct
"Do It" just makes it easier.

Lets see if we can describe what's going on, it might help.

(note: for simplicity sake these are fixed pressure FPRs,
the factory and the add on,
change pressure in response to a changing manifold pressure)

This type FPR controls the pressure in the line to it
by by-passing excess pressure into the return line.**

The return line has near zero pressure normally.

Lets say for example only, that FPR1 is set at 35 psi.
If the return line is pressurized by FPR2 higher than the FPR1 is set at, (lets use 50 psi)

The excess pressure down to 35 psi can not be bypassed into a line with 50 psi on it.

Thus, the resulting pressure is 50 from FPR2 back to the pump.
see this crude sketch.

FRP setup


A simple test for people with a fuel pressure gauge is to squeeze closed the
return line with a pair of needle nose pliers.
The harder you squeeze, the higher the system pressure will go,
up to the max pressure of the pump.

** There are relief valves that control pressure by allowing the pressure after them to be set -
these are called "pressure relief valves"
Often used in boost/waste gate control set ups.

Does this help?

#6 Myxalplyx

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Posted 11 February 2005 - 03:06 PM

Okay both are correct
"Do It" just makes it easier.

Lets see if we can describe what's going on, it might help.

(note: for simplicity sake these are fixed pressure FPRs,
the factory and the add on,
change pressure in response to a changing manifold pressure)

This type FPR controls the pressure in the line to it
by by-passing excess pressure into the return line.**

The return line has near zero pressure normally.

Lets say for example only, that FPR1 is set at 35 psi.
If the return line is pressurized by FPR2 higher than the FPR1 is set at, (lets use 50 psi)

The excess pressure down to 35 psi can not be bypassed into a line with 50 psi on it.

Thus, the resulting pressure is 50 from FPR2 back to the pump.
see this crude sketch.
Does this help?


I understand fully! Thank you Skip and DoItSideways. I was concerned that putting the aftermarket RRFPR downstream of the stock unit could somehow damage the stock unit making it malfunction, even seize up or something. Sometimes I may get carried away with questions and trying to be careful with the simplest of things. I'm learning though. I'll tinker with it over the weekend. Thanks again!

*I'll be back later with fuel injector questions no doubt* I'm going to have to remove them at some point to send out. ;) Tune up the car and get some more numbers with more boost.

#7 Myxalplyx

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Posted 15 February 2005 - 04:28 PM

*sigh* I'm starting to feel like an idiot. I play with car some 15 minutes or so every other day because I'm working like a pig for an upcoming project. So there's little time to work on the RX.

Today, I was just trying to locate the fuel pressure regulator. I thought I found it previously but.......I was wrong. You see, one of the pics I provided above is the EGR as DoItSideways stated.

The other two pictures I provided is not the fuel pressure regulator. The piece I'm pointing at in the two pics is just to the right of the EGR. This this is connected downstream of the fuel filter. It's called a 'Damper'.

What is strange is that my Factory Service Manual (FSM) doesn't show the 'fuel damper' downstream of the fuel filter on the MPFI turbo'd cars. It shows the fuel damper downstream of thefuel filter on the SPFI RXs. On an SPFI car, this damper then connects to the fuel pressure regulator which then goes to the fuel injectors.

On an MPFI turbo car, the fuel filter goes through a fuel delivery line right to the fuel injectors. The FPR is connected somewhere else between the left and right sides of the fuel injectors. I'm stumped!

SPFI = Fuel Filter ->Fuel Damper ->Fuel Injectors
MPFI Turbo = Fuel Filter ->Fuel Delivery Line ->Fuel Injectors
My RX Turbo = Fuel Filter -> Fuel Damper -> Fuel Injectors


I can not find the fuel pressure regulator to save my life. :banghead: Teh Newb!

I have a 1987 FSM but my car is a 1988 RX turbo so maybe that explains some things. Besides the diagram in the FSM, nowhere else in the FSM is there any mention or picture of the FPR. So I can't determine where it's at on the car.

So I am seeking higher wisdom from the higher ups here. Can you tell me where I can physically find the FPR (or what it's next to), so I can install my RRFPR? Yes, I'm slow so please forgive me. Thanks!

#8 Skip

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Posted 15 February 2005 - 06:40 PM

see if this helps

little tuff from your pict but
the input fuel line should be connected to
the injectors

And is a larger diameter than the return line


Here is a bit of a trick you can skip

If you ever need some gasoline
(like for the lawnmower or such)
You can connect a piece of fuel line to the
FPR return hose barb, start the car and
a nice controlled flow of petrol
will eminate from the hose)


(sorry lost my FTP connection have to use the board)

click this -> FPR Location

#9 Do It Sidewayz

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Posted 15 February 2005 - 06:43 PM

dude....screw finding the stock FPR it is burried!!!!!

as i said before...just locate your return line that goes to the tank.

Mount the RRFPR on the firewall someplace, and run a new piece of Fuel Injection hose to the RRFPR inlet, then a new piece from the RRFPR outlet to the metal return line (behind the driver's side strut tower).

Then just give the RRFPR a boost/vacuum reference......i'm sure you have a boost gauge...so just T that line.

Tighten the clamps and jack is your uncle

#10 Myxalplyx

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Posted 15 February 2005 - 08:29 PM

*deleted*

#11 subyrally

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Posted 15 February 2005 - 10:12 PM

im glad i saw this post, now i know how to set up my regulator, but i thin that i might hit up the msd catalog and build a custon fuel delivery syste, for my spyder manifold. that way, i can get injsctors in any flow rate i wants without worrying about the little hoses.

#12 Myxalplyx

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Posted 17 February 2005 - 06:29 AM

Posted Image

Skip, your picture helped me a ton. Thanks! I have to point out a couple of things though.
1: The 'Fuel in' in this pic is my 'Fuel Out',
2: The 'Fuel return' in this pic is my 'Fuel in'. That's where my fuel filter is connected too.
3: The 'Intake Manifold' line goes to the driver's side of the car down into some abyss. ??????
4: There is a 4th metal line about an inch down from your black line pointing to the 'Intake Manifold'. It's behind that little black wall there in the pic. That line connects to the EGR thingy that I asked about earlier.

I'm sorry my picture wasn't expanded large enough for you to get a full view. My bad! If I didn't you'd probably have seen the extra line or so or maybe pointed out differently.

In my ignorance, I did not know that was a FPR. I assumed a fuel pressure regulator would have the 'Fuel In' line coming from the top or the side and the 'Fuel Return' line coming out from the bottom of it. I kept feeling for the 'Fuel Return' line on the bottom of the FPR and couldn't find it so I thought it wasn't a FPR.

At any rate, 'Scrappy' is running great. Feels like wings are on the side of the car. I tested it at 5-6psi around the neighborhood and down some streets. I turned the RRFPR up from '0' psi to 48psi.

It idled fine at '0' psi and I was stumped until I remembered it's measuring fuel pressure after the stock FPR. So, if you see '0' psi, don't be alarmed. It's just letting all the fuel return to the fuel tank that's coming from the stock fpr (which is regulated at stock fuel pressure).

I'm not sure how to tune it this way since putting any pressure on the fuel return line should raise the stock fuel pressure. I set the RRFPR at 48psi and drove around like this. I thought about this at home and will be taking it back down to '0' psi (which should be stock FPR) and going from there on the dyno. I'm thinking 48psi on the fpr is actually 48psi on TOP of the stock fuel pressure.

Now that the RRFPR is added, new ignitor, new spark plug wires, disty/rotor and new plugs (will add spark plugs tomorrow).....time to go back to the dyno to see what fueling can do for your RX turbo. Stay tuned!

#13 4WDFrenzy

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Posted 17 February 2005 - 06:55 AM

That's cool. I bypassed my stock FPR all together. I have mine set at 42psi base fuel pressure. The car seems to love all the extra fuel especially since I turned the boost up another psi to 11psi. I've been toying around with the fuel pressure and ignition timing for a couple of days now trying to find the perfect combination since I'll be going to the track this weekend.




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