Lift Pumps: Remove Air : HOW?

[RJWEST]

I see several after market Lift Pumps with water seperators/filters,

that advertise that they condition fuel and " Remove Air "



How,& Where does the air go,



Splain to me Lucy... ... Pless.

 

[Allnew2Me]

The pumps that claim to remove entrained air all use a fuel return line that goes back to the tank. They have a fuel inlet, an outlet that supplies fuel to the engine and another that goes back to the tank, usually by way of a fitting that replaces the rubber hose on the filler neck. I have asked about how they remove air and never really got a solid answer to that question.

 

[rweis]

The VP44 bypass back to the tank removes air as well. Maybe not as well as the FASS, but the engineering of the bypass valve is at the physical top of the VP44 body and put there so that air could be passed back to the tank.



I do not know what type of air though, entrained air or free air.



I feel the return bypass valve concept like the RASP uses helps remove some of the air because the fuel stream is constantly moving and being bypassed to the tank or goes through the VP44. Notice I said I FEEL, I have NO empirical evidence to back up my thoughts that there is less air. I do have hard copy descriptions of the details fo the VP44 that say the VP44 bypass valve is designed to return air back to the tank.



Bob Weis

 

[steved]

In the FASS, it uses the principle that entrained air floats.



The fuel pickup (for the engine supply) is near the bottom of the particulate filter, the return line to the tank pulls off the top of the filter. As the air works through the filter media, it rises to the top and gets returned to the tank. And since there is much more volume of fuel getting pushed to the return line than to the engine, the air is "encouraged" to move to the return line.



Actually quite simple...



steved

 

[LowFly]

Im a little short on time at the moment... . but i will post these:





#ad




ALSO Click Here for a Vid Demo

 

[Gary - K7GLD]

About the only way to separate air bubbles from fuel flow, is to somehow use the law of physics - air usually RISES in a solution - so using that standard principle, air reducing systems usually have to include a point of separation, and also a separate route to vent/return trapped air outside the system or back to the fuel tank.



In my own system, using a Walbro GSL392 high PSI/flow rate pump, a return line and regulator was necessary anyway, so I decided to orient the positioning of the regulator/return to the TOP of the assembly in order to encourage and enhance the separation and return of trapped system air back to the tank in the return line:



#ad




This install may work especially well, since this assembly is physically located just inches ahead of the VP-44 itself, and as Bob pointed out, the VP-44 itself also provides for separation and return line venting of entrapped air as part of it's internal design, using the same principle.

 

[RJWEST]

Thanks all; Keep rereading info, Still a tad skeptical... .

Where does air come from? When filling tank is the Foam,
fuel vapor or Air, My guess is fuel vapor,

With the Air remover systems , I assume they work as advertised
But, To me it does not seem that the Fuel would be in place long enough to remove all the air/vapor... Probably helps But ???

My Thoughts, Bigger supply line from inside fuel tank to prevent ANY cavitation from forming Vapors/air bubles... .
IE If LP has no restriction from tank, smooth fuel flow...
which would place in question a too large a LP for application. .

Thanks for your patience from a relative NEWbe.

 

[Gary - K7GLD]

Thanks all; Keep rereading info, Still a tad skeptical... .



Where does air come from? When filling tank is the Foam,

fuel vapor or Air, My guess is fuel vapor,



With the Air remover systems , I assume they work as advertised

But, To me it does not seem that the Fuel would be in place long enough to remove all the air/vapor... Probably helps But ???



My Thoughts, Bigger supply line from inside fuel tank to prevent ANY cavitation from forming Vapors/air bubles... .

IE If LP has no restriction from tank, smooth fuel flow...

which would place in question a too large a LP for application. .



Thanks for your patience from a relative NEWbe.

WELL, as far as I'm concerned, the issue of "air in fuel", and promotion of "systems" designed to provide significant VP-44 or engine function improvement due to "air removal", is another of those urban legends and old wives tales. Sure, there is undoubtedly SOME air/vapor that naturally gets entrapped in the fuel flow from LP action and other system peculiarities - but as has been pointed out, the VP-44 design already covers that with an internal air separation design that then feeds any air back to the tank in the fuel return line.



Is it likely that MORE air might be "generated" in the fuel system - perhaps by overkill pumps that provide FAR more PSI and flow than the VP-44 wants, needs or can use? Probably - but in those cases, significant efforts to then REMOVE that air is pretty much an admission of a system that is poorly designed, and NEEDS the added "crutch" to remove the air it ITSELF has created in the fuel flow!



The VP-44 is fully capable of separation and removal of any NORMAL air/vapor in the fuel flow - and if a system needs extra design or gadgets to remove air, it's most likely the air that that system ITSELF has created!



And yeah, I fully realize my above OPINION will generate volumes of screams of anguish and denial from the makers and users of those systems - but that's life... :-laf

 

[RJWEST]

Gary, Some very good points, along with what I had been
thinking, But did not want to bias any replys. .

My thought is ( with fairly stock Truck )
an adequate , reliabe fuel system, without excessive fuel
pressure, allowing the VP44 to manage the volume and air rejection.
Guess I Gotta go back and reread all the old posts again.

 

[Bob4x4]

If removing air was relevant to power or mileage the oem's would make a larger issue out of it. They don't ! we dyno'ed both stock and modified 24 valve trucks before and after FASS systems were installed... ... ..... no improvement at stock or 400 hp level.



Bob

 

[RJWEST]

Thank you Mr Bob4x4, Good Info...

 

[CEkstam]

WELL, as far as I'm concerned, the issue of "air in fuel", and promotion of "systems" designed to provide significant VP-44 or engine function improvement due to "air removal", is another of those urban legends and old wives tales. Sure, there is undoubtedly SOME air/vapor that naturally gets entrapped in the fuel flow from LP action and other system peculiarities - but as has been pointed out, the VP-44 design already covers that with an internal air separation design that then feeds any air back to the tank in the fuel return line.



Is it likely that MORE air might be "generated" in the fuel system - perhaps by overkill pumps that provide FAR more PSI and flow than the VP-44 wants, needs or can use? Probably - but in those cases, significant efforts to then REMOVE that air is pretty much an admission of a system that is poorly designed, and NEEDS the added "crutch" to remove the air it ITSELF has created in the fuel flow!



Hi Gary,



Let me answer that question for you! (REMEMBER, YOU ASKED)





The quest to separate air, specifically entrained air from diesel fuel and also vapor has been attempted unsuccessfully, by many, since 1892. If you study these earlier attempts by the patents that are registered with the U. S. patent office and also the PTO's of other countrys, you will see a maze of these devices. The Fuel Preporator, which was developed starting in 1990, is currently the only true fuel air separator on the market. There are bubble eliminators out there which, to some extent can separate fuel and air. I will explain that.



First, damage to injection system components caused by air in fuel is a known issue and is fully addressed in all diesel engine manufacturer's service manual trouble shooting guides.



Second, the affect of air on the performance of the diesel engine that utilizes a barrel/plunger assembly to inject fuel is well understood by the industry. The compressibility of air and fuel vapor delaying the pressure build up in a barrel/plunger type injection system and causing retarded injection timing is what has led to the development of the common rail. In the common rail, the spray of fuel into the cylinder is caused by the release of fuel from a high pressure reservior, the common rail, by a computer (ecm) controlled valve.



Removal of air from the fuel!



The removal of air from the fuel by the Fuel Preporator system, developed starting in 1990 and of which the AirDog is the smallest model, happens as follows:



The air separation details of the following narrative can be found in the Fuel Preporator patent 5,746,184. This patent has a priority date of 1992.

Fuel with entrained air flows from the tank, through the lines, through the wire screen water separator and into the pump of the AirDog. Now we have positive pressure under our control. The fuel flow coming from the tank is drive by atmospheric pressure trying to equalize or satisfy the demand of the pump. From the pump the fuel flows under pressure into the filter, the filter fills. Fuel passes through the filter leaving the separated air bubbles behind. As I pointed out in my 1992 patent 5,355,860 Cummins explained this in their Service Topic 5-135. Air is separated from the fuel by the resistance of the passage of air through the wetted filter element. This is why filters on the vacuum side of a pump are most always low or partially filled.



So, now the air is separated, it can float to the top of the dirty side of the filter (this is important, remember it). The Fuel Preporator/AirDog has a bleed hole at the top of the filter (dirty side) to discharge the air into the return to tank line. Note, the fuel (without air) passes through the filter element. Inside the filter element, extending down from inside the nipple that holds the spin-on filter in place, is a pickup tube (we call it a depth extension tube). This is the passageway that takes fuel from the bottom of the filter element for the engine. It is extends to the bottom to take fuel that is free of air bubbles that may randomly pass through the filter and also air that was in the filter from filter changes.



The space between the nipple and the depth extension tube is the port for the fuel the engine doesn't need to flow back to the tank. Again, any air in the filter from filter changes or that has randomly passed through the filter may return to the tank with the fuel. Located in the return passageway is a regulator that maintains internal pressure. This is what sets the out to engine pressure. The primary air exit port, mentioned earlier as the tiny air bleed hole on the dirty side of the filter, enters the fuel return passageway after the regulator. This is important, as the regulator closes as fuel demand from the engine or the filter restricting the fuel flow as it gets dirty, the separated air can still get out.



The Fuel Preporator also has flow dividers, patent no. 6,729,310. These separate the dirty side of the filter into an inlet side and an outlet side. With these features, the little AirDog can separate air at flows in excess of 150 gph. Without the flow dividers, it would take a 5" OD filter to do the same. Without the primary gas exit port and the flow dividers, our tests show that the system will stop separating air from the fuel as the regulator closes and or as the flow to the engine exceeds 30 to 40 gph.



The FASS has only the depth extension tube extending up to a passage way that goes out to the engine and the fuel return passage with the regulator feature for air separation. The air is separated by the filter in the Fass . All of the separated air is trapped on the dirty side of the filter where it stays until the equilibrium point is reached. It is then forced through through the filter where it emerges as larger bubbles, no as the tiny bubbles of entrained air. If the regulator is open and flow velocities are low enough for the bubbles to float, it can rise up and return to the tank. If the regulator is closed, the passageway to the engine is the only exit from the system. Additionally, if the velocity of the fuel through the system is to fast for the air to float up out, the air will again go with the fuel to where ever the fuel goes.



I hope this will help you to understand how these fuel / air separation systems work!



Please excuse the typo's!



Charlie

 

[Gary - K7GLD]

With all due respect to the above - and thanks for providing it:

First, damage to injection system components caused by air in fuel is a known issue and is fully addressed in all diesel engine manufacturer's service manual trouble shooting guides.

I would submit, and propose that the FACT that random air in the fuel system IS "a known issue", that engine and fuel system makers have pretty well dealt with and provided OEM designs that will in all *normal* situations, deal with that vapor in a totally adequate manner - at least in the VP-44 IP, that issue is addressed internally as part of the pumps basic design.



Added to that, is my suggestion that much of what is mentioned in the above quote relative to air in the system relates primarily to air LEAKS in the system and "troubleshooting" to find and eliminate those leaks potentially causing engine and related issues, rather than what minute and random air that more commonly might be normally present in a properly functioning system. In that case, it makes far more sense to locate and eliminate the leaks, than to install gadgets to remove it!



The basic issue here as it relates to Dodge/Cummins owners is, is there any NEED or benefit for added attention or installation of extra devices to remove air, over and above that already provided. AND, if entrapped system air IS to be found over and above normal OEM recognized levels, WHERE does it come from - and is the installation of a aftermarket pump and filtration system to bleed that air off the BEST system for that purpose - or are aftermarket system THEMSELVES the primary source for that excessive air generation to begin with?



To be more specific, do any documented studies exist relative to our trucks, clearly showing that in a properly functioning OEM setup, excessive, damaging air is present?



If not, and if added, excessive air at compromising levels are only introduced AFTER significant fuel system mods have been done, we're back to my original opinion that air reduction function in fuel systems are there basically to correct what those systems themselves have created.



I'm not trying to be argumentative here - but the makers and sellers of the "Air Reducing" setups seem to be claiming that in the NORMAL operation of our trucks, there IS significant and potentially damaging air in our fuel stream that the OEM has failed to deal with, and that THEIR setups are needed to correct that issue - is that actually the truth, or simply largely advertising hype?



I'd be very interested in seeing any independent test documentation you might have available that counters any of what I have stated...

 

[CEkstam]

All petroleum based liquids contain varing degrees of entrained air. Cummins issued Service Topic 5-135 in 1965 to explain why the primary fuel filters were always low or partially filled when removed for filter changes. In March, 1990, Caterpillar issued Special Instruction 651-1250 stating that diesel fuel contains up to 10% air. Parker Racor published a bulletin authored by a Mr. David Hodgkins, a 40 year diesel fuel system engineer) stating "Fact #1: There id AIR entrained in diesel fuel. " And Milwaukee School of Engineering, Handbook of Hydraulics page 4 Table of Contents: VI Effects of contaminants upon hydraulic fluids... !. Air, A... Source and effects of air contamination... 1. Dissolved air... 2 Entarained air & foam... Page 82. . Itis estimated that 75 to 85 percent of hydraulic system failures are a direct result of fluid contamination... 88. There are two types of contaminants, Fluids and Solids. Probably th most destructive fluid contaminant is "Air". It goes on and on! Cavitational pitting of the barrel, galling of the barrel / plunger assembly, tip erosion and tip loss.



Once you really get into the study of this subject you will find it absolutely hard to believe that it has been around since day one of the diesel engine. If you would go to our temporary website, ( search under AirDog, Fuel Preporator or PureFlow Technologies, click on Pureflow Technologies) you will find a detailed narrative on the affects of air on injection timing, fuel economy, power output, exhaust emissions, and how air damages the injection system.



Just putting a vent line on a vessel with diesel fuel in it will not separate the entrained air from fuel. This has been done for decades, to no avail, only the large bubbles or free air will float out. That is if the velocity/turbulance of the flow is low enough for the bubbles to float.



It is all very interesting!



Charlie

 

[brods]

Interesting, yes. Charlie why have you not mentioned dissolved air? Is it not present in diesel? I was under the impression that dissolved air is drawn out at pressure drop situations. Does the air dog induce a pressure drop to intentionally draw out any dissolved air?

 

[Gary - K7GLD]

All petroleum based liquids contain varing degrees of entrained air. Cummins issued Service Topic 5-135 in 1965 to explain why the primary fuel filters were always low or partially filled when removed for filter changes. In March, 1990, Caterpillar issued Special Instruction 651-1250 stating that diesel fuel contains up to 10% air. .



Once you really get into the study of this subject you will find it absolutely hard to believe that it has been around since day one of the diesel engine. If you would go to our temporary website, ( search under AirDog, Fuel Preporator or PureFlow Technologies, click on Pureflow Technologies) you will find a detailed narrative on the affects of air on injection timing, fuel economy, power output, exhaust emissions, and how air damages the injection system.



Just putting a vent line on a vessel with diesel fuel in it will not separate the entrained air from fuel. This has been done for decades, to no avail, only the large bubbles or free air will float out. That is if the velocity/turbulance of the flow is low enough for the bubbles to float.



It is all very interesting!



Charlie

Thanks Charles - appreciate the comments and pointers - but here's a few points:



I'm really not too overwhelmed by potentially outdated fuel and system studies done 40 years ago (1965), or 17 years ago (1990) - there have been LARGE changes in both fuel AND pumping systems since those early studies - from original high-sulphur diesel, thru LSD and ULSD - and from older style rotary injection pumps thru the P series, VP-44 and now the common rail stuff, as well as changes in injectors themselves.



Additionally, I found this quote from your pointers to be interesting, in regards to testing parameters used to establish their findings:

These diesel engines are all equipped with the conventional 'vacuum feed' filter system.

That would seem to NOT apply to our pressurized fuel systems, where the fuel is not "vacuum feed", but pressurized by way of the OEM LP.



Changes in diesel formulations, refining and transport have also occurred. So, are all the same fuel conditions now the same as in those decades earlier - and have vehicle fuel systems been improved to better deal with what was earlier claimed regarding fuel quality?



I'll ask again:



What tests regarding fuel entrapped air has been done in OUR trucks in RECENT years - say during the 2nd generation to present trucks - and is there any independent testing documentation available that backs up/verifies testing done on diesel fuels 40 years ago?



We have seen examples of our trucks making 500K miles - and some over the million mile mark - WITHOUT unusual failures or special attention to air entrapment in fuel systems - and what efforts do the 18 wheeler manufacturers use OEM in that regard in their million mile engines - seems like they would be VERY sensitive to that issue, if there is one - in the trucks they make their livings off of - wouldn't such a sensitive and damaging issue be treated OEM, if the technology is easily available to counter it - especially with all the added claimed benefits available to offset the expense? OR, is this actually a "tempest in a teapot" - an issue actually of rather limited occurance in real-world, day-to-day operation?



On the face of it, claims of as high as 10% air entrapment in current commonly available fuel supplies seems VERY far fetched - I'd sure like to see documentation verifying that claim - then maybe we could try for a corresponding 10% reduction in the pump price because of the AIR we are being charged for! :-laf:-laf



Very interesting subject - worth further discussion!



Best regards



Gary

 

[CEkstam]

Good comments Gary,



One thing to keep in mind, no one is going to highlight a problem they cannot fix. Here is a little experiment to try with the diesel fuel you are putting in your truck today. Take an empty plastic soda bottle, clean it and fill it about half full of diesel. Cap it, of course. Now hold it on its side in front of a good bright light. Slosh it back and forth as it would if you were driving. Observe how the bubbles start folding into the body of fuel. Now, shake hard and hold it still in front of the light. At the proper angle to te light you will very clearlly see the tiny bubbles just hang there. When the University of Illinois studies were done, they took very clear pictures of these samples, enlarged them many times and every time, you could see more smaller bubbles in the back ground. It was like looking at the stars first with the naked eye and then through stronger and stroger telescopes. By the way, the Cat Special Bulletin 651-1250 featured a site glass, in fact that was what the bulletin was about, selling a site glass, so you could see dthe air and not blame you know who for low power. I will scan that document so I can post it, tomorrow. Think about this, why is there such a big market in anti foaming agents for hydraulic systems? It is the viscosity/surface tension, amount of agitation, and temperature of the liquid that determines how much air can be entrained in the liquid. A lift pump/transfer pump will pump whatever enters enters its inlet!



The OEM's have fought this issue for a long long time. The primary filters on a class 8 truck engine operate under a partially filled condition today, just as they did in 1965. It hasn't changed with todays fuels. Lost torque at 1,200 to 1,500 rpm hasn't changed either. Starting about 1980, the class 8 engine manufacturers started re-engineering their engines to operate/pull at those rpm ranges. They also went from machanically controlled injection systems to ECM controlled, and now the common rail. They are still improving the common rail system.



This discussion can go forever, don't you think?



Thanks



Charlie

 

[CEkstam]

Sorry, I missed the question about dissolved air. There is no such thing as dissolved air. Sugar, salt and many other substances dissolve but air never dissolves. I specifically questioned a very knowledgeable person at 20,000 Rotunda Drive in Dearborne MI about why the scientific community continually makes that statement when referring to entrained air. He said something to the tone of Well, it just started out that way. He then admitted that air can never really dissolve.



Charlie

 

[Gary - K7GLD]

Sorry, I missed the question about dissolved air. There is no such thing as dissolved air. Sugar, salt and many other substances dissolve but air never dissolves. I specifically questioned a very knowledgeable person at 20,000 Rotunda Drive in Dearborne MI about why the scientific community continually makes that statement when referring to entrained air. He said something to the tone of Well, it just started out that way. He then admitted that air can never really dissolve.



Charlie

I never saw a question about "dissolved air" - must have missed it too...



As to testing typical diesel fuels for entrapped air, I would think a better "test" would be to completely fill a bottle with diesel, then tightly cap it - then let it sit for a few days or weeks, allowing the air to rise to the top and visually see how much the diesel level drops in relation to whatever air pocket results. Or do the "experts" claim that air STAYS in suspension, and never separates on it's own? I have done that same "test" in my own experience - by filling 5-gallon containers with diesel fuel for extended periods, and have NEVER seen any visible change in fuel level over the storage period - and I would think anything approaching 10% would be pretty obvious...

This discussion can go forever, don't you think?

YUP - I suppose so - and I'm admittedly skeptical over this subject as a significant, typical real-world issue for most of us. Added to that is my also admitted skepticism of some of the more extreme and radical claims in hyped advertising - often "supported" by "test results" lifted out of context from a wide variety of ancient or possibly slanted or questionable sources.



Not claiming that is necessarily the case here, but simply making a point - and as the owner of a diesel powered truck, my second, I have NEVER seen even the slightest evidence of the type symptoms or operation of those truck engines as described as commonplace in the pointers you have supplied.



My truck has operated smoothly, idled perfectly, without random missing, or white smoke at startup or after, and power has been smooth and consistent in application across it's full RPM spectrum in routine driving as well as heavy towing and dyno runs. And I doubt my fuel supply during the 175,000 miles or so of diesel operation has been any better than that used by most owners.



Another member further above has recounted his own dyno experience in both stock and modded truck before and after installation of FASS systems, and noted NO change in measured power or engine operation - hard to understand IF there was 10% of air removal taking place and it's claimed damaging effects were being removed in those cases.



I guess this is another of those "Your mileage may vary" issues - and probably the actual value of the air reduction systems as they typically apply to our specific trucks may well fall more into that "warm and fuzzy feeling" after one is installed, than by actual measurable benefit...



BUT, you're probably right, we may have pretty well beat this subject to death - and it falls to the readers to decide for themselves the "dangers" of air entrapment in typical diesel fuel supplies, as well as the "value" of aftermarket air removal systems...



CHEERS!



Gary

 

[CEkstam]

Brods brought up the question of "dissolved air"



Regards.

Charlie