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D-jet fuel pressure regulator. Whats inside and how it fails
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raygreenwood
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PostPosted: Fri Jun 03, 2016 3:23 pm    Post subject: D-jet fuel pressure regulator. Whats inside and how it fails Reply with quote

So a couple of weeks ago, in a thread on type 3 forum we were talking about leak down of the D-jet fuel pressure regulator. I could not remember what the diaphragm inside was made of. Year ago, as these regulators failed on me I use to occasionally cut one open to find out WHY it failed.

Back in those days I had good magnifying devices and good cameras….but I had no access (mid to late 90s’) to a combined microscope and photography outside of black and white 35mm…which I have some of those in one of my archives….but I do have all of this now….and I got intrigued enough to revisit and share.

So…some basics:

1. This and most fuel pressure regulators..…haave a precision ground metering plate inside, mounted on a diaphragm with a spring pressure on it.

2. That metering plate bears against a precision machined or ground outlet “nipple” or orifice.

You can think of the nipple as a garden hose and the metering plate as putting your thumb over the end to increase the pressure on the hose.

NOTE: except in this case its built backwards The “hose” is the outlet and the metering plate keeps the chamber around the end of the hose under pressure. That pressure must fight the metering plate back away from the outlet nipple by building pressure against the surrounding Viton diaphragm…that the spring is bearing against. The diaphragm simply multiplies the area of force.

3. In our regulator, you have a simple screw bearing against the back side of the spring putting pressure against the diaphragm….which has the metering plate attached to it…and hence against the outlet nipple.

Basic failure modes/problems:

1. System leak down:

A. For fast starting and to keep enough pressure on the fuel to prevent fuel in the system from evaporating until the engine cools down (causing vapor bubbles and lowering pressure), both the FPR and the fuel pump check valve need to be able to keep a minimum of about 50% of normal engine running pressure for about 24 hours.

B. With D-jet ….The bump of the key and the 2.5 second fuel pump pulse will normally bring the line pressure back up to about 85% of running pressure…which is about 22- 23 psi.

There is not really a “specification” for this that I have read…but many years of experience have shown that this is what new systems run and ….about 20-23 psi is the bare minimum pressure for correct fuel spray pattern and close to normal dosage of fuel……just like pressure over 35 psi on this injector type can cause a stream pattern. There are limits in both directions.

C. When the pump is known not to be the issue…or when testing by crimping off the supply line immediately at engine shut down to get an idea of the FPR bleed down speed, the pressure will normally on a new FPR…drop to about 21-23 psi immediately. Within about 1-3 hours….it drops to about 16-18 psi. Overnight it can drop to 11-13 psi and can stay that way for days.

A FPR regulator that drops to below about 21 psi on shut down is leaking. It will usually also show rapid drop…within 30-45 minutes….to the 16-18 psi range. Overnight it can be below 10 psi or down to “0”.

2. Fuel pressure stability problems:

In most cases when the pump is known to be very fresh or new, with a good quality FP gauge…and with the ignition timing CORRECT (ignition timing affects injection timing and greatly affects fuel pressure stability)…AND with no injectors leaking………..

NOTE: Correct running fuel pressure (by basic factory standards) means the fuel pressure gauge needle very rapidly will vibrate/move from 27 to 29 psi at steady running….with no more than a 1.5 psi drop to about 26.5 psi for a split second upon acceleration. This means that you have no significant FPR leak down and fuel pump volume is adequate to keep up with flow demand.

A. If the fuel pressure gauge reading stability has needle fluctuations greater than a +/- 1 psi on a setting of 28 psi….the FPR is leaking very slightly….meaning a spread of more than +/- 1 psi or a drop greater than 1.5 psi on acceleration.

B. The inability to keep a stable fuel pressure at running but the ability in general to produce baseline fuel pressure specification of 28 psi...can many times be misinterpreted to be poor fuel pump volume output….which is why I always recommend checking that FIRST…so you know what it is NOT.

If your pump is in poor condition, there is no usefulness whatsoever in testing fuel pressure or adjusting and testing the FPR.

3. Leaking from the screw and inability to adjust properly or keep stable fuel pressure is caused by a cracked or ripped rubber diaphragm so fuel is on both sides of the diaphragm and causes an equilibrium and leaks through the threads.

NOTE: the threads on our D-jet fuel pressure regulator are not airtight…nor do they have to be. Some people have a stated belief that atmospheric pressure on the spring side of the diaphragm is part of the control mechanism.

I can tell you for sure than with 35-45 psi of spring load on the diaphragm and total movement during metering of less than .002”….2 cubic inches of normal atmosphere trapped on the spring side of the diaphragm exerts virtually no force. However…installation of a vacuum index nipple on this regulator (as many have done)…exerts a great deal of assist force.

Causes of regulator failure:

1. Rust and corrosion. Old regulators that have sat for long periods with gasoline in them…and most gasoline has some moisture and alcohol…develop rust flecks on either the metering plate or exit nipple. Small flecks cause slow leak down. Large flecks cause fast leak down.

2. Wear to the metering plate from harmonic vibration (super-fast opening and closing of the metering plate as fuel is rhythmically pulled from the ring main by injection’s). A fair amount of this over say…50-70k miles is normal….but it is made worse by WIDE pressure swings…caused by weak fuel pump and/or poor injection timing.

3. The harmonic mentioned above.....also works in combination with the harmonic that comes from the fuel pump. The fuel is taken in at ambient pressure (near 0 psi) and compressed by the rollers in the cells.

As it reaches the end of the rotary cycle inside the pump....and vents to the port that allows access to the fuel ring main....you get a "pulse" from the exit from the roller cell and since the ring main is under nearly identical pressure. This pulse is happening at the frequency the rotor in the pump is moving.

You also get a back pulse....as the fuel tries to reenter the roller cell but is blocked. Its more of a "slam". ...and the line pressure that is causing that back pulse.... has a fluctuating harmonic from the injectors opening and closing....which causes fuel pressure to go up and down....rapidly at a different number of pulses per second than the fuel pump.

This combination of interleaved or interspersed harmonics causes a hum or buzz in the pressure regulator at certain engine rpms. This is the metering plate in the regulator....chattering with this harmonic.

It does not cause fuel pressure issues....but it does wear the metering plate out faster. if you also have some light rust specs on the metering plate....you can very quickly have a regulator that leak down very fast as the plating erosion on the metering plate increases.

IMPORTANT NOTE:
I first noticed that last finding during the initial period of time when I first started using the Compufire brand points replacement module. It’s bracket was originally ill fitting inside of the 205P distributor.
It caused quite a bit of extra distributor body movement required for proper ignition timing. This brought the injection timing out of phase a bit and caused other running and tuning issues.

Over a period of 5 months driving like this….. somewhere in the middle of which I diagnosed that the change in injection timing causes wide fuel pressure fluctuations at idle and low rpm….of about +/-3-4 psi….which is a spread of 6-8 psi (because the injection timing change affects vacuum signature greatly)….by finally getting a very good gauge and tracking this issues…….during that five months I went through TWO brand new Bosch fuel pressure regulators. The symptom was perfect pressure to start with. Within a month or so….very fast leak down even though the gauge would maintain baseline pressure.

It seemed to mimic a weak pump or a pump with poor voltage. Cutting open the regulators showed excessive wear to the metering plate……and the cause was excessive pressure fluctuation caused by the injection timing.
The gist is:….once the FPR starts leaking to a certain extent (for whichever reason)….it becomes inefficient at maintaining pressure and makes the normal plate harmonic worse….and accelerates wear to the plate.

The gallery Part # 0 280 160 001 / 311 133 030 :

Historic note about this fuel pressure regulator: This one lasted quite a while and was installed after I had sorted out injection timing and fuel pressure issues.
After about 1 year…about 60K+ miles….it started leaking down excessively. Immediate drop to about 19 psi after shutdown and morning after readings of about 6-8 psi. I figured it was a rust fleck or vibrational wear starting.

The pressure drop never got worse because I was backstopping it with another worn regulator (good trick) set to about 3-4 psi less. But when it got to the point that at idle it would develop a harmonic hum…I got a new one….so….let’s see what is inside.

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This is the top/spring side.

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Looking into the top half showing the spring, the spring seat and the adjusting screw in the center

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Spring removed

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Spring and seat

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Diaphragm, spring and seat. Notice the detail of how well the diaphragm is crimped to the spring seat. These are very well made.

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The metal button in the center is the metering plate. A very useful design feature is that the metering plate is installed in a clip with a spring and has a ball guide on the back…so the metering plate is self-correcting for any angle so it has precision fit against the outlet orifice. Very well designed.

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A close view. The ring you see on the metering plate….is primarily EROSION…..and some corrosion. This is mainly from the harmonic wear I spoke of earlier.

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A 60x microscope shot

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A series of three 220x microscope shots of different segments of the erosion ring.

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This is the outlet orifice. Note the black corrosion speck….more on this in a minute.

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This is a 60X microscope shot of the area. Notice the fine machine marks.

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And at 220x you can see the actual rust damage/pits that started the initial slow leak down.

My Personal Fuel pressure regulator rules:

1. I don’t buy used regulators. Virtually all of them are a waste of money. Virtually all of them have some wear or corrosion. These regulators are still made as far as I know and readily available new.

Examples:
http://www.summitracing.com/parts/bch-0280160001?seid=srese1&gclid=CKnnqYvyjM0CFQEJaQodO1UA7A

http://www.autohausaz.com/search/product.aspx?part...aQodLfUDyw

http://www.partsgeek.com/98zfn42-volvo-1800-fuel-p...+Regulator

http://www.rockauto.com/en/catalog/volkswagen,1972...om+URL+%2F

2. Make sure what you buy has been stored properly. They should come in a box with plastic caps on both ends.

3. If you plan to store a spare or carry it in the tool box….release all the pressure you can from the adjusting screw, take a blunt metal or hard plastic pick of about 2mm diameter (I use an Allen key) and insert it in the return side to push the metering plate away from the seat…spray in some synthetic oil…no solvents and no WD-40. Put the caps back on and put it in a plastic bag.
This keeps the metering plate and outlet orifice from rusting.

Ray
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PostPosted: Sat Sep 30, 2017 12:20 pm    Post subject: Re: D-jet fuel pressure regulator. Whats inside and how it fails Reply with quote

Hey Ray, excellent write-up, as usual, thanks!

The Rock Auto link at the bottom shows an L-Jet regulator, while the PartsGeek and Summit pages both show the D-Jet regulator you're talking about. Oddly enough, the Rock Auto page lists the shown regulator as fitting all the L-Jet air-cooled Volkswagens, as well as the 411 and 412 except for 1973. I'm not sure what's up with their catalog; it's usually quite good.

What kind of synthetic oil would you recommend for pickling/storing a good new FPR? Motor oil? Or something like SuperLube?

Thanks,
Robbie
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PostPosted: Sat Sep 30, 2017 1:19 pm    Post subject: Re: D-jet fuel pressure regulator. Whats inside and how it fails Reply with quote

asiab3 wrote:
Hey Ray, excellent write-up, as usual, thanks!

The Rock Auto link at the bottom shows an L-Jet regulator, while the PartsGeek and Summit pages both show the D-Jet regulator you're talking about. Oddly enough, the Rock Auto page lists the shown regulator as fitting all the L-Jet air-cooled Volkswagens, as well as the 411 and 412 except for 1973. I'm not sure what's up with their catalog; it's usually quite good.

What kind of synthetic oil would you recommend for pickling/storing a good new FPR? Motor oil? Or something like SuperLube?

Thanks,
Robbie


I would be afraid of motor oil or ATF. I am still not sure exactly what the diaphragm composition is. Most probably a viton or chlorinated neoprene.

I would use something like the Superlube.

https://www.walmart.com/ip/Super-Lube-Synthetic-Mu...mp;veh=sem

Wally world says they have this. I have one around and it works well. Ray
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PostPosted: Sat Oct 07, 2017 5:29 pm    Post subject: Re: D-jet fuel pressure regulator. Whats inside and how it fails Reply with quote

There's an oil called Corrosion X which is meant specifically for preservation and rust prevention. It's available from most aviation supply shops, Grainger, Amazon, etc. and typically costs about $18 for an 18oz can. It's what I use for keeping spare parts in new condition.
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PostPosted: Mon Oct 09, 2017 5:34 am    Post subject: Re: D-jet fuel pressure regulator. Whats inside and how it fails Reply with quote

blankc72 wrote:
There's an oil called Corrosion X which is meant specifically for preservation and rust prevention. It's available from most aviation supply shops, Grainger, Amazon, etc. and typically costs about $18 for an 18oz can. It's what I use for keeping spare parts in new condition.


Thank you for the product tip! I took a look at that products SDS sheet.....and have to say it looks to be excellent for this purpose.

Its two main ingredients are a mineral oil and what,theyccall a hydro treated neutrsl base oil.

There should be no issues with that on the rubber diaphragm. I will give it a try! Ray
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PostPosted: Sat Nov 03, 2018 2:29 pm    Post subject: Re: D-jet fuel pressure regulator. Whats inside and how it fails Reply with quote

nice write up! i have a question - is the original bosch fpr from an injection model type 3 suitable for use with twin carbs (solex pdsit 2/3)?

is it adjustable, and if so, what's the range? might it be too high for carbs? been trying to search info on this but no luck to date.
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PostPosted: Sat Nov 03, 2018 3:41 pm    Post subject: Re: D-jet fuel pressure regulator. Whats inside and how it fails Reply with quote

daos wrote:
nice write up! i have a question - is the original bosch fpr from an injection model type 3 suitable for use with twin carbs (solex pdsit 2/3)?

is it adjustable, and if so, what's the range? might it be too high for carbs? been trying to search info on this but no luck to date.


The D-jet fuel pressure regulator is fully adjustable......but....I do not know if it will adjust down low enough for carbs. I actually doubt it would be accurate without pulsating down in the 2-3 psi range. Its normal pressure range is 28-30 psi.....and it does not seem to hold pressure down below about 10-12 psi for long.

It may be worth checking just for the knowledge. Ray
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PostPosted: Mon Dec 14, 2020 6:04 pm    Post subject: Re: D-jet fuel pressure regulator. Whats inside and how it fails Reply with quote

Jesus, this is a good thread. Thank you Ray!

Just a quick update, I've been using this Pressure regulator with good luck on my 71' D-jet system.

https://www.rockauto.com/en/moreinfo.php?pk=10910628&cc=1370089&jsn=11374


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PostPosted: Mon Dec 14, 2020 7:51 pm    Post subject: Re: D-jet fuel pressure regulator. Whats inside and how it fails Reply with quote

Mr.Duncan wrote:
Jesus, this is a good thread. Thank you Ray!

Just a quick update, I've been using this Pressure regulator with good luck on my 71' D-jet system.

https://www.rockauto.com/en/moreinfo.php?pk=10910628&cc=1370089&jsn=11374


Image may have been reduced in size. Click image to view fullscreen.


Thanks!...and thanks for another source for an FPR! Delphi generally makes good components.

Just for those looking on....they note the diaphragm is "Nitrile"...well...probably not just Nitrile ...but HSN (highly saturated Nitrile) or HNBR (Hydrogenated Nitrile butadiene rubber)....works great with fuel and oils and is the green rubber o-rings used in AC systems.

Ray
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PostPosted: Mon Dec 14, 2020 8:04 pm    Post subject: Re: D-jet fuel pressure regulator. Whats inside and how it fails Reply with quote

raygreenwood wrote:
Mr.Duncan wrote:
Jesus, this is a good thread. Thank you Ray!

Just a quick update, I've been using this Pressure regulator with good luck on my 71' D-jet system.

https://www.rockauto.com/en/moreinfo.php?pk=10910628&cc=1370089&jsn=11374


Image may have been reduced in size. Click image to view fullscreen.


Thanks!...and thanks for another source for an FPR! Delphi generally makes good components.

Just for those looking on....they note the diaphragm is "Nitrile"...well...probably not just Nitrile ...but HSN (highly saturated Nitrile) or HNBR (Hydrogenated Nitrile butadiene rubber)....works great with fuel and oils and is the green rubber o-rings used in AC systems.

Ray


Ray, do you have any photos how those CIS injector seals install on a type 3?

They seem way too fat to flex around the injector, or sit into the bore of the type 3 intake manifold.

I'm tempted to install them, but have not seen any photos here on Thesamba about them.
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PostPosted: Tue Dec 15, 2020 7:05 am    Post subject: Re: D-jet fuel pressure regulator. Whats inside and how it fails Reply with quote

Mr.Duncan wrote:
raygreenwood wrote:
Mr.Duncan wrote:
Jesus, this is a good thread. Thank you Ray!

Just a quick update, I've been using this Pressure regulator with good luck on my 71' D-jet system.

https://www.rockauto.com/en/moreinfo.php?pk=10910628&cc=1370089&jsn=11374


Image may have been reduced in size. Click image to view fullscreen.


Thanks!...and thanks for another source for an FPR! Delphi generally makes good components.

Just for those looking on....they note the diaphragm is "Nitrile"...well...probably not just Nitrile ...but HSN (highly saturated Nitrile) or HNBR (Hydrogenated Nitrile butadiene rubber)....works great with fuel and oils and is the green rubber o-rings used in AC systems.

Ray


Ray, do you have any photos how those CIS injector seals install on a type 3?

They seem way too fat to flex around the injector, or sit into the bore of the type 3 intake manifold.

I'm tempted to install them, but have not seen any photos here on Thesamba about them.


I will see what I have.....but they work better precisly because of what you described.

You will need to securely hold the injector.

If its your first time putting them on.....cap the fuel inlet side and then find a 1/4" drive deep socket that the capped fuel inlet barb just fits into.

Take that socket and either insert it into a hole on a wooden work bench or clamp it in a vise. The object being to hold the injector stable and vertical while you use both hands to 8nstall the CIS o-ring. This is mainly necessary if you still have the yellow or black plastic injector pintle covers.....which I hate and remove.

With a cotton swab put some light oil or grease....just on the inside of the o-ring. You do not want it sloppy.....but you need a little lube and don't want it on the outside where you will slip off the o-ring.

Push it straight down onto the injector end. It will take a bit of force to get it to expand. Just when you think it will not fit....it will snap down. But it may have some stretch todque on it and it may try to pop back off.

To stop that.....hold it down with your fingers and give it a half rotation twist and it fixes it in place.

The outer diameter prevents it from fitting into the well around the port in the manifold end.....but once you tighten the bracket up that holds tbe injector....it compresses about 50% of the thickness of the o-ring down into the well...sealing both the outer/upper edge of the port counter bore and all the way to the ledge in the inner bore.....and forces the injector to be dead center and allows "0" movement.

Ray
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PostPosted: Sat Feb 27, 2021 12:50 pm    Post subject: Re: D-jet fuel pressure regulator. Whats inside and how it fails Reply with quote

Does anyone remember what the upper end of the adjustment range will provide in PSI? I have one of these D-jet regulators still new in a box from about 2013 (when the Bosch units were still readily available), with the intent of using it on a MSII conversion (that wants to see about 42-48PSI, or 3 Bar), but this project is finally coming together and was wondering if it is still a viable solution, or if I am better off moving to something like The Dub Shop''s fuel regulator, that uses the early 2000s 3 Bar Bosch/VW regulator insert.

If it helps, I am using a CIS pump. I am aware of the lack of vacuum reference on the D-jet regulator, and the possibility of modifying one into it, but just want to know if the more modern regulator is better suited (or is it better built or worse?) than the ancient D-jet unit.
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PostPosted: Sat Feb 27, 2021 4:55 pm    Post subject: Re: D-jet fuel pressure regulator. Whats inside and how it fails Reply with quote

jsbeddow wrote:
Does anyone remember what the upper end of the adjustment range will provide in PSI? I have one of these D-jet regulators still new in a box from about 2013 (when the Bosch units were still readily available), with the intent of using it on a MSII conversion (that wants to see about 42-48PSI, or 3 Bar), but this project is finally coming together and was wondering if it is still a viable solution, or if I am better off moving to something like The Dub Shop''s fuel regulator, that uses the early 2000s 3 Bar Bosch/VW regulator insert.

If it helps, I am using a CIS pump. I am aware of the lack of vacuum reference on the D-jet regulator, and the possibility of modifying one into it, but just want to know if the more modern regulator is better suited (or is it better built or worse?) than the ancient D-jet unit.


They can do 3 bar no problem. When they get to about 4.5 bars they get iffy.

Ray
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PostPosted: Sat Feb 27, 2021 5:50 pm    Post subject: Re: D-jet fuel pressure regulator. Whats inside and how it fails Reply with quote

Thanks for the pressure info Ray. Any opinion on relative merits or quality of these D-jet regulators vs. the newer insert style Bosch units that I previously mentioned (something like the Bosch 0280160557 3 Bar unit on early 2000's Golf/Jettas)?
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PostPosted: Sun Feb 28, 2021 9:52 am    Post subject: Re: D-jet fuel pressure regulator. Whats inside and how it fails Reply with quote

jsbeddow wrote:
Thanks for the pressure info Ray. Any opinion on relative merits or quality of these D-jet regulators vs. the newer insert style Bosch units that I previously mentioned (something like the Bosch 0280160557 3 Bar unit on early 2000's Golf/Jettas)?


The build quality is virtually the same in the D-jet versus L-jet or digifant regulators. The mechanism TYPE Ais virtually the same.

You get small differences in detail and diaphragm sizing because the L and digifant models are vacuum indexed. But they pretty much work the same and with age or with moisture are prone to the same failure modes. This is not saying any of them are not dependable. Its actually time and lack of running that kill regulators and not so much huild quality.

As far as the "accuracy" of the later Mk2 style insert regulator versus the earlier actual L-jet......from what I have seen, the later regulators were a little more accurate in just how they worked......but overall vacuum variable regulators are not very accurate just because of the variability of the vacuum signature itself.

It was really a crutch in earlier injection systems like L-jet and digifant...because the system itself did not have the range of upper end rpm and under load fuel volume control required via pulsewidth alone.....without having excessively large injectors that then introduce their own contollability issues.
Having a few more psi at WOT and at part throttle helped for gross enrichment....with the ECU/system controling the fine detail via pulsewidth and the 02 sensor. But having or allowing the pressure regulator to control a fairly wide range of fuel pressure and not being controlled by the ECU meant that the system could only be so accurate for fueling.

The even more modern systems like mk 4, 5, 6 and on.....use a a fairly accurate fixed system with the regulator in the fuel filter located far aft at the tank. Structurally this means the MAIN fuel supply is smoother and more pulse free.

And of course the more modern injection with more sensor inputs has wider pulsewidth lattitude ro fully control fuel without havibg to have the rising rate variability. At least that is how most of the 2.5L work.

But....some of the GTI and others.....use the same system I just listed......but still have fine pressure variability at the rail.....but using an electronically variable valve.....basically a solenoid.

Personally.....if the programmable system you are going to has wide enough adjusting lattitude.....and.....maybe even an 02 sensor ......I would try a fixed D-jet style regulator fed by the modern version of fuel pressure regulator like the golf and jetta mk 4 and onward use.

But either way the regulator you are looking at is better overall than the early L-jet and digifant regulators. Ray
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PostPosted: Sun Feb 28, 2021 4:35 pm    Post subject: Re: D-jet fuel pressure regulator. Whats inside and how it fails Reply with quote

Once again Ray, a million thanks for this virtual Masterclass thread covering all aspects of fuel pressure regulators; that was even more detail than I expected.

The only part of your last reply that I did not follow was the reference to using "a fixed D-jet style regulator fed by the modern version of fuel pressure regulator like the golf and jetta mk 4 and onward use". Do you mean literally in series? I was not aware that was a workable option, as I rarely (perhaps never?) see references to FPRs placed in series. If you are saying this is optional, and the D-jet regulator (alone) I already have can handle the flow/pressure regulation duties produced by a CIS pump, I will likely run it that way, without the added complications of a second FPR.
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PostPosted: Sun Feb 28, 2021 10:13 pm    Post subject: Re: D-jet fuel pressure regulator. Whats inside and how it fails Reply with quote

jsbeddow wrote:
Once again Ray, a million thanks for this virtual Masterclass thread covering all aspects of fuel pressure regulators; that was even more detail than I expected.

The only part of your last reply that I did not follow was the reference to using "a fixed D-jet style regulator fed by the modern version of fuel pressure regulator like the golf and jetta mk 4 and onward use". Do you mean literally in series? I was not aware that was a workable option, as I rarely (perhaps never?) see references to FPRs placed in series. If you are saying this is optional, and the D-jet regulator (alone) I already have can handle the flow/pressure regulation duties produced by a CIS pump, I will likely run it that way, without the added complications of a second FPR.


Understand....that the new systems...say Mk4 through Mk 6 for sure and probably 7 and 8....use a LARGE fuel filter that has a 4 bar regulator built in.

Image may have been reduced in size. Click image to view fullscreen.


Fuel comes in one side...goes through a 4 bar regulator (an identical 6 bar is also available)...goes through the filter and to the front of the car.

This filter/regulator assembly is right next to the fuel tank. The excess regulated fuel goes right back to the tank.

The object is that having a large reservoir of fuel i the filter and a large pressure head of fuel...way in the back....creates very SMOOTH and STABLE fuel pressure. The standard oscillation from the pump...is non existent. It is also more pressure than the system needs in the case of the GTI and some Audi models that use the 6 bar regulator.

Having high smooth volume at higher than necessary pressure...means that there is virtually "0" fluctuation and none of the vehicles use or require a vacuum variable regulator.

Most of the five cylinders at 4 bar....use it straight fom the pipe and work with pulse width only. The GTI's and others...use a secondary...fine adjustment regulator that is electronic and very small...that drop the pressure further. So they really run a fixed pressure.

The object is filtering and regulating very close to the tank ...long distance from the engine...our tank in the front and engine in the rear is just fine....and starting out with more pressure than you need...and regulating down.

One of the issues with D-jet.....is fuel pressure oscillation/variation. I plan on mine to use a better than stock pump...turbine ring modern pump..smoother to start with than roller cell....and go through a 4 bar regulator filter....a fuel pot or accumulator near the fire wall in the back...and then do the 28 psi regulation with the stock D-jet regulator.

I think this method would help with your set up as well. Ray
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PostPosted: Sun Feb 28, 2021 10:49 pm    Post subject: Re: D-jet fuel pressure regulator. Whats inside and how it fails Reply with quote

Wow, more food for thought; but in some ways, a bit too late to make yet another adjustment to my (what I thought was carefully planned out) system.

As it stands now, I am using the complete fuel pump assembly (with mini surge tank surrounding the pump) and integrated large(-ish) filter from a 1990 16V Passat (CIS). This setup is really almost what you describe, minus the very cool pressure regulating filter. The portion that is the mini surge tank surrounding the pump is also where the return line runs into, then the excess is sent back to the fuel tank from there.

While I do admire the elegance of the setup you just described, let me know what you think of what I have currently assembled. It may have some of the stabilization effect you describe from the large filter closely coupled with the pump (and sitting right under the fuel tank in the right side well, behind the beam), then a moderate length back to the engine, through the fuel rails/injectors, onto the (adjusted to 45PSI) D-jet FPR, and back into the return line and onward back to the surge tank and return to main fuel tank.

Am I setting myself up for trouble here?
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PostPosted: Thu Apr 08, 2021 7:11 am    Post subject: Re: D-jet fuel pressure regulator. Whats inside and how it fails Reply with quote

By the way......and I meant to post this point back when I originally posted yhis thread and the regulator microscope shots.

When I showed the black flecks of rust on the machined metering outlet of the regulator.......I meant to "get back to" the reasons they look so deep and black like they are.

The very shiny surface of that metering outlet orifice......is either nickel electroplate or "electroless" nickel plate.

This is significant because:

1. Nickel plating DOES NOT RUST.......
2. Nickel plating....especially electroless nickel plate.......is very, very hard and wear resistant after they plate it and bake it. Like about 70+ Rockwell.

3. The problem is.....that unlike a zinc plating which is a sacrifical anode and prevents rusting over a wide area......but is too soft of a metal for a high frequency wear area like this..........nickel is NOT a sacrifical anode.
The nickel itself will NEVER rust. BUT......if the plating is cracked, chipped or gouged to make any kind of opening through the plating to the metal below........the metal underneath the nickel plating.....will rust in all directions.....creating a crater or erosion cavity behind the nickel plate.....and eventually there is no metal left to support the nickel plate.....and that spot cracks asay leaving the effect you see in those microscope shots.

So what causes the original cracks in the nickel plating inside of the regulator?

I suspect......that its just the violence of the millions of cycles of harmonic opening and closing.
But.....its also the fact that these were PROBABLY....nickel ELECTROPLATED back in the day......and not ELECTROLESS nickel plated.

Those fine machine marks are little valleys. When you are doing electroplating.....the current follows the path of least resistance. It would tend to flow to the high peaks of those fine machine marks.....depositing thicker nickel there....and thinner nickel in the valleys.

Electroless nickel.....does not use electricity. It uses an acid or base mixture to cause electrochemical reaction at the surface of the ferrous metal part you are plating. In short....it makes its own electricity for plating.

So.....the electroless nickel plate.....gives a surface thickness uniformity that is many times better than standard nickel electroplate.

Its also damn expensive....solution wise..... and was probably not in as wide of use back in the 1960s. Ray
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