Car= 2003 XKR Coupe, 4.2L S/C, 6 speed ZF auto, approx 89,000 miles

The bad mojo continues.

Fuel Pulsation Dampers

"It appears not a question of IF but WHEN it will leak."

Since completely disassembling the top of my engine (to gain access to the fuel rail), having the seal of a leaking pulsation damper "fixed" by a professional, then reassembling the engine - plus nearly three months of chasing an unknown electrical gremlin brought to life by the above service (including disassembly/reassembly of the engine a second time while chasing said gremlin) - I have had 1400 great miles fantastically satisfying driving!

Thats the good news. The BAD news is that in the last two weeks I have started to smell gasoline at cold start ups once again. Several days ago, I confirmed my future service nightmare.

The SAME pulsation dampener (bank 2 fuel rail) is drip drip DRIPPING fuel again!!!!!

Exactly like five months ago, the damper drips (one drop every four seconds) when the engine is started from cold and within five to seven minutes of driving it stops leaking - and as long as the engine is at operating temp it (for now) doesn't leak.

I know fixing the leak will require a ridiculous amount of aggravating work and that, without question is in my future.... but I have a plan!

First, a theory:

After hours and hours of interwebs research, plus several phone calls to professional high performance engine builders, I have realized that I am NOT alone with my problems. Many cars equipped with the EFI fuel rail dampers are having or have had these dangerous fuel leaks.

I have begun to believe that the huge amount of fuel problems we are starting to see on the forums are caused by the stupid amount of ethanol in the fuel available here in the USA. Our fuel system's plastic parts and rubber seals are not dealing well with this alcohol... Although, in Kansas City, we can still find an occasional fuel station that sells gasoline that is advertised to be blended without ethanol, they are few and far between - which it not very practical for daily driving and the 30-50 cents per gallon higher price for this fuel is annoying.

Now, my plan:

I am going to dig back into my engine to get at the fuel rail and put a definitive end to those pesky pulsation damper leaks forever!
(Radiator, Belts, All hoses, Thermostat Manifold, Throttle Body & TB intake manifold, Charge Air Coolers & Supercharger plus engine wiring harnesses) ALL have to come off - about 5 hours of work just to get to the fuel rails)

I am going to disable the pulsation dampers - block them off... I will backwards engineer our trusted Jaguar engineer's design. I have much support in this idea from many sources, including the company from Houston, TX - that did the injector cleaning and put new seals on my fuel rail dampers five months ago.

Seems apparent that one of the main reasons the dampers were installed on our cars to begin with was to make the EFI system more quiet. High pressure systems without damping tend to "ring" or make a "clickity clickity click" sound when in operation. The "let's make the luxury car quiet" theory certainly seems well supported - considering the ungodly amount of "muffling" our exhausts have from the factory. Indeed, buyers of $90,000 cars certainly must not be expected to put up with the "low brow" sounds of a V8 engine at work... right?!

There ARE other reasons that, in theory, these dampers were put into place. Chief amongst those are to make the fuel delivery somewhat smoother within the rails. In EFI systems where injectors fire in tandem (like in-line sixes) the fuel pressure at the injectors can vary quite a bit (when sets of injectors open & close at the same time) - that's what the pulsation dampers help to control. However, in EFI systems that are sequential (like our V8 Jags) huge sudden "dumps" of pressure are not encountered - so the dampers are not as essential in providing a "smooth" flow of fuel within the rail. Also, the size of the rail (or more specifically, the quantity of fuel the rail contains) is a factor effecting fuel pulsation caused by injectors firing. The larger the quantity of pressurized fuel available in front of the injectors, the less pulsing will occur.

Given that I don't care that I can hear my injectors firing (I LOVE the sounds of mechanical cacophony) and I believe that our fuel rails (with their long, circuitous nylon hose that winds around the supercharger snout) holds quite a bit of fuel - I'm gonna give the "no-damper will exist to ever leak again idea" a go.

I'll keep you all posted on how I block them off and the progress/results in future posts.

Support research:

I have heard a number of reports that OEM pulsation dampers (located on
fuel rail) has leaked in automobiles - and even resulted in fires! It
appears not a question of IF but WHEN it will leak.

In my research about pulsation dampers I ran across information from
builders of high performance aircraft engines - some of which are
adapted from automotive powerplants. I quote: "Don't use a pulsation
damper. They are not necessary with today's smoother (less-pulsing)
aftermarket pumps. These dampers have been deleted by every aircraft
builder that I am aware of due to a significant potential for internal
leaking."

Injector-Rehab Fuel Injector Cleaning Services

Fuel Pulsation Damper. What is it?

A fuel pulsation damper is a device used to regulate the oscillation of
fuel caused by the injectors opening and closing and smooth this out.
Sometimes referred to as a FPD. At this time I do not have a diagram to
show you, so you will need to use your imagination as I describe it the
best I can.
The damper uses a diaphragm to absorb pulses or waves in the fuel. If
you could picture what would happen if you were to have a large beach
ball in a pool and "bounce" the ball half under the water, let it come
up and repeat several times. Waves would form. The injectors opening
and closing against the pressure sent by the pump causes the same waves
in your fuel system. The damper's diaphragm is used to absorb these
waves and smooth the fuel delivery.
Many people say you do not need the pulsation damper, other will tell
you that you do. The ones that say you do not need it more than likely
either heard of someone or themselves had an engine fire due to the
pulsation damper failing. The ones that say you do need it may have
heard stories of an injector failing because there was no pulsation
damper. The failure of the injector was caused by the fuel hammering
the injector so hard that it failed. I have never personally seen an
injector in this state (remember we se A LOT of injectors) and still
feel this is an urban legend. If you happen to have an injector in this
state, please let me know. I would LOVE to test and analyze it.

If you are running an aftermarket fuel pressure regulator, more than
likely there are dampening capabilities built into the regulator. I
know for a fact that Aeromotive regulator use this technology but I am
not sure about others. Mounting the aftermarket regulator as close to
the fuel rail as possible will eliminate any need for additional
dampening. The Aeromotive units will regulate the flow by creating a
stable and smooth flow.

In short, a pulsation damper does serve a purpose, but is not
"nessessary".

Many cars like the Mazda RX7 are equipped with a fuel pulsation damper
that is prone to failing and causing an engine fire. If you plan on
retaining the FPD you must keep an eye on it. Replace it BEFORE it
fails and you loose your car to a fire.


More very interesting information on fuel injection systems here:
Knowledge Base

 

I agree with your analysis of the potential cause of seal failure, I also have a 2003
XKR with 33xxx miles but have not seen a leak. Could the problem in your area have contributions from the local fuel additives.
I remember from a few years back the Maryland area experienced natural gas explosions in a few homes that were thought to be caused by seal failures from a new source of LNG. I'm not sure if this was ever confirmed since the news reports dried up.
Good luck with your approach, I'll be watching with interest.

 

Maxwdg,
Once again you have my sympathy, as I've said before you don't deserve this amount of bad luck.
A very interesting post.
I have no idea how these fuel rails fit together or what they're made of.
Do they use O rings?
My life (literally) depends on O rings and other flexible seals and I've had some interesting moments with them.
There is no doubt that chemical mixtures have completely different effects on seals from their constituent parts.
We use rapeseed oil to test some of our equipment which uses Viton O rings. Viton is a fluoropolymer resistant to almost everything.
One day someone substituted used cooking oil and the seals dissolved. This is impossible since Viton is resistant to all oils and their likely thermal breakdown products but it happened.
I don't know what the fuel rail seals would be - possibly nitrile rubber which is reasonably resistant to petrol and highly resistant to ethanol - but a mixture of the two - GOK !
Maybe if it is just O rings the answer would be some really resistant material like Simriz.

 

@maxdawg

If you want to retain the function of the fuel damper there may be a couple of solutions.

First, is the idea of a anti-hammer trap as found in household plumbing. It is nothing more than an air bubble trapped at the top of a vertical pipe stub. As air is compressible, it absorbs the standing wave when someone shuts off a tap suddenly. If you put a valve at the top of the trap, then it is possible to renew the bubble if it disappears. You would then depressurise the system, open the valve and let the air bubble be replenished. There are commercial versions of this type of device.

Alternatively, you could also plumb in a small version of a pre-oiler tank. It is the same as above with the two sides separated by a piston. It may not be as effective because of the mass of the piston moving around since it is designed for pre-oiling.

So, a few fittings and you have a reliable replacement device to serve the function of the damper. If you use steel tubing bent to exit somewhere convenient before the stub, you'll be able to access the stub without taking things apart.

 

The talk surrounding gasoline is "ethanol" or "biofuel" made from "biomass". It is fairly imprecise.

The cooking oil could have been based on canola, corn, "vegetable", olives, grapes ad inifintum. At least it is labelled on the jug.

There is no such labelling on gasoline.

The point of course is that the ethanol content could be any biomass source or any combination of biomass, with or without trace contaminants.

Now ... watch the nay sayers proclaim ... loudly ... that "ethanol" is perfectly benign to automotive fuel systems.

phase separation in ethanol blended gasoline:

 

I don't know what's in that beaker of yours, Plums, it certainly looks evil.
Ethanol, as us wine drinkers know, mixes well with water whereas petrol doesn't.
Ethanol is considerably denser than petrol ( 0.79 as opposed to 0.71-ish) and this will get worse as the ethanol absorbs water and, in the process, becomes less miscible with hydrocarbons.
Petrol in the US contains detergents including alkylamines and alkyl phosphates at the level of 50-100 ppm.
These levels may be raised in ethanol mixes to keep the alcohol from separating - effectively acting as emulsifying agents.
These chemicals are exceedingly damaging to some seal materials and may, for example ,facilitate the penetration of one of the major fuel components into the seal.

The point about Viton vs cooking oil is that Viton is highly resistant to ALL oils/grease/fats/waxes and this just shouldn't happen.
Interestingly the automotive industry is quietly shifting to very exotic seal materials
Polyimide Parts & Shapes | DuPont? Vespel®
perhaps they already see a problem here.

 

The beaker is the fuel drained from a lawnmower after several months of storage. The site owner explains that the top layer is dark because of the two stroke oil. The bottom part is phase separated ethanol. Phase separation is the process whereby the ethanol binds with water and then drops to the bottom.

It is a well known effect in the marine world because recreational marine engines can sit for extended periods without running. It is also the cause of formerly reliable diesel and turbine generators not coming online during power outages at data centers. Just read the accounts about failures to maintain power at premiere tier one date centers on the east coast during the recent hurricane. NY dropped power deliberately and the data centers dropped like flies.

If you plug ethanol, viton into the big G, you will come across a study by Dupont about ethanol and viton presented at some conference.

There is also an article from the fuel handling industry on the first page, the people who move the ethanol around and they don't like the effects of ethanol on their equipment one bit. Those are people who can spend *huge* sums of money on the best components available to industry ... and they don't like ethanol.

BTW, Dupont notes that a 25 percent concentration of ethanol in their standard testing fuel which is named "Fuel-C" is more corrosive than either 100 percent gasoline or 100 percent ethanol. There must be some interaction there.

 

BTW, Dupont notes that a 25 percent concentration of ethanol in their standard testing fuel which is named "Fuel-C" is more corrosive than either 100 percent gasoline or 100 percent ethanol. There must be some interaction there.

Exactly the point I'm making with the unknown oil mix.
We're used to looking at chemical resistance against a pure or (usually water) diluted chemical, so Viton is fine for molten sodium but hopeless for MEK.
- as you rightly point out Viton gets an 'A' rating for either alcohol or petrol but mix the two and it is 'not recommended'.
Going off topic - I can still buy alcohol free petrol (and beer should I be foolish enough) but our tractor diesel now contains 10 % ethanol.
This reduces the power output - ethanol has a molecular weight of 48 of which 16 is oxygen - by about 8% so the increased fuel consumption pretty much negates the alcohol content as well as making the fuel hygroscopic.

 

Hopefully, the carburetor on that tractor has a brass float. There is an article you can find about a plastic float that had been "pickled in ethanol" for x hours. Not pretty.

Did you know, that as of the time of the Dupont presentation there were 6 grades of Viton(tm)? Some better than others depending on the fluid involved. Makes you go hmm...

Overall, ethanol has not benefited Johnny Jaguar one bit. Indeed, it has made him to significant expense in downloaded repair costs.

BTW, the reason that high ODBII LTFT trims without a vacuum leak seem to get no real notice by the EU techie types is .... ethanol/fuel grade. They just don't see it as frequently, if at all. Running two tanks of 91 AKI fuel(premium) will knock a persistent 10+ percent LTFT on both banks with no apparent cause down to circa 2 percent LTFT. 20/20 hindsight says that the ECM was upping the fuel feed due to the effects of the 87 AKI(regular) fuel while in closed loop.

 

Are you suggesting our tractors are so ancient they run off TVO?
We've stopped using Viton since the dissolving incident and use either Simriz or Chemraz depending on what delightful fluid we have to contain.
Costs ten times as much, but who cares.

 

Here is a good site to visit for finding ethenol-free fuel, I pulled up KS for you.

Ethanol-free gas stations in the U.S. and Canada

Here in WI the ethenol-free Premium 91 Octane is cheaper than Ethenol laced Premium by a dime and is fairly easy to find. I use it in everything.

Some motorcyclists and PWC guys "distill" their own by doping 5 gallons of fuel with a little water, which encourages the ethenol to phase out quickly, and then drawing it off the bottom. You are left with pure fuel. Add some octane boost and you can custom make fuel to your specifications. Pretty hard core.

15% Ethanol is coming.

 

Wow! I'm glad that other's certainly seem to share my theory that alcohol may be a culprit in the destruction of a lot of fuel components in cars that are 8-10 or more years old. I am not a chemist, so this talk of formulas, density and the like is kinda going over my head! But it is fascinating, and I'm learning from all of these general propositions. (They cause me to go on google fests!)

I hate hearing that even higher percentages of alcohol may be in our future. Thanks Spurlee for throwing out the link to "pure-gas.org." I have been using that site for a year or so to find stations that provide non-"alcolaced" fuel. There was a grocery-store chain (Hy-Vee) that just put in a pure-gas pump about a month ago near my home! The price of the pure 91 octane fuel yesterday was 23 cents/gallon above the 89 octane "mid-grade" alcofuel. That's not so bad! Prior to that station opening, the closest retailer to me, was a 20 mile out-of-the-way round trip and it was 45 cents/gallon above the premium fuel price! THAT was a bit difficult to afford for daily driving fuel - so I have not been using "pure gasoline on a regular basis in my XKR. I hope that Hy-Vee does continue the reasonable priced pure gas - I plan to use it as much as possible in the future.

I will say, at this point, I'm still unaware of what precisely IS causing the damper to leak - in fact I have taken one of the dampers off of a salvaged fuel rail that I bought off of Ebay and can see that the leak may wll be coming from TWO places... Either the O-ring seal or the damper construction itself.

I am going to shoot some pics of that salvaged damper later today and post them so that we can all form ideas - based on actually looking at the damper itself.

Then, when I take the five hours to actually tear my engine down to get to the specific leaking part - I will, of course, try to bench test the damper and make an attempt to determine the source of the leak.

 

Everybody always wants to blame ethanol for every fuel leak or fuel problem, but the facts are that if ethanol was causing all these problems, there would have been a million lawsuits by now. But to your problem, GM and ma mopar learned a long time ago to put fuel dampners in the gas tank, not sure why anybody in their right mind would not as these always wear out and I would not one to start leaking on my nice hot engine.
I had my first replacement one in my vette last 2 weeks, second lasted 3 months and the final one was still going strong after 3 yrs when I sold the car and about 35-40k miles. Not sure about the 1st one, but the second I bought off ebay, was vitron type seals (that is what the ad said), so be VERY careful buying auto parts, I have been seeing a lot of misleading advertisements and package information the last couple of years. Got one part from a well known online parts house that had a delco box, but the part was definitely not. They refunded my money, including shipping and sent me a new part and it was delco.

Just be wary about the parts you buy, might not be the case in your situation, good luck!!

 

That is not a fact about the effects of ethanol, that is a supposition based on extrapolation.

That does not explain failures on original factory installed parts that have not been touched.

 

Maxwdg,
Never mind all the high falutin' stuff - please let's see how the thing is put together (i.e. seals) when you get it to bits.

 

Here are some detailed pics of the dampers I removed from the salvaged fuel rail I purchased on Ebay.

The dampers are held onto the fuel rail "cups" by metal tabs crimped onto the flared edge of the "cups."

I am thinking theses dampers can ONLY leak from two places:

#1 the O-ring. Since these are not the dampers from my car I can only guess that they were not leaking. After the tabs were pulled back, the dampers were very hard to pull out of the "cups" because the O-rings were such a tight fit. Examination of the condition of the blue O-rings tells me that they were good. The fuel rails were still full of old residual fuel and plenty spilled on my shirt when I removed the first damper..... Stinky!

#2 the crimping around the damper. I would imagine, just like the old oil pressure sending units from GM and Mopar cars were prone to do as they aged... Fuel could be leaking from this internal seal, right?

When I actually get my XKR's damper out I will do a series of pressure tests to hopefully determine where the leak is coming from. I MAY simply remove the damper "cups" and silver solder the two holes in the fuel rails closed... Don't know yet. Another idea (if the leak doesn't seem to be leaking past the O-rings) would be to machine two stainless plugs to a few thousands larger than the input tube to the dampers and "press fit" the plugs into the damper tubes... That will stop any fuel from leaking around the "crimp."

For the record, the rating on the dampers say 380kPa (51psi)

Enjoy the pics!

 

How about silver soldering the seam?

 

That's odd, the fuel pressure on the 4.2 is actually 65 psi, and on the SC engine 76 psi under max boost. From what car was this fuel rail?

Edit: Maybe this is the internal pressure setting of the unit.

 

It certainly isn't a safety margin I'd like to work to !
There's a big old moulding flash on that O ring - how much does it squeeze when it goes in ?
If you've got callipers the OD of the O ring unsqashed and ID of the rail socket would be good.
Also what do the O rings on the injector fittings look like?

 

For the record: The photos and mesurements ARE NOT from the fuel rail on my car. My car is still drivable and I'll continue to do so before the wintery mix weather hits in the next week or so. At that time, I'll pull it into my shop and start the job of dismantling the engine... I have confirmed again today, that the pulsation damper on my car only leaks when the engine is cool - once it is up to operational temp there is NO leaking at all. It drips about once every 4 seconds down into an intake manifold runner valley at start up and then subsides within 5-7 minutes of running. With very careful observation using a bazillion candlepower flashlight and a long wooden medical Q-tip the damper seems to be leaking around the crimp - but thats kind of hard to ascertain - to be sure.

The fuel rail and injectors we are observing through my pics and measurements was obtained by me as an investigative mule - from Ebay. It was misrepresented to me by the seller as being from a 2006 XKR S/C 4.2L.
What I received was certainly NOT from a supercharged car. I have no clear idea what year car was from - but I know it was from a normally aspirated Jag/Ford/Rover AJ V-8.

I tried to trace the injector numbers to determine the exact year, but I ran out of patience after searching for about an hour on the web. Perhaps one of you guys can tell me.

Injectors are beige in color, have only four spray holes at the business end and have these part numbers and words on them DENSO 8DB A, FoMoCo
0480 887 07, 6R83-AD

The Injectors were were not nearly as hard to work out of the cups on the rail as the dampers were - but still, they were very secure.


Plums: Although my plan is most likely to disable the dampers on my XKR (so it really wouldn't matter if the heat destroyed the diaphragm inside the damper) silver soldering the crimped seam may make the clips that hold the damper on to the fuel rail cup difficult to bend in far enough to grip the cup and thus hold the damper with the O-ring in place. I'm still leaning toward machining two stainless plugs to a few thousands on an inch larger than the ID of the input tube to the dampers, "press fitting" the plugs into the damper tubes and refitting the damper into the rail with new O-rings.

avos: See above comment about fuel rail origination - I too, had questioned the 51psi rating I saw on the damper that we are looking at so far in this thread - after seeing over 70psi at the Schrader valve of my '03 XKR 4.2L last November when I replaced the fuel pump.

Steve: I have many measurements for you and all to peruse. Also, you will note the the injector O-ring doesn't have near the casting flash that the blue Damper ring.

Please keep in mind that these are USED O-rings and the OD X and Y axis difference may be caused by the rings having taken a "set" from a long in-service, installed time.

Fuel Rail Cups ID (both Dampers and Injector cups) = 13.49mm

Damper input tube ID = 6.66mm
Damper input tube OD =7.93mm at seal seat

Damper O-ring ID = 7.70mm
Damper O-ring OD (diameter) = 14.35mm
Damper O-ring OD (X axis) = 3.75mm (see picture below for Axis Key)
Damper O-ring OD (Y axis) = 3.33mm

Injector O-ring OD = 14.00mm
Injector O-ring OD (X axis) = 3.77mm
Injector O-ring OD (Y axis) = 3.17mm