G'day All
I've been having an air in fuel problem with my 02 KJ 2.5Lt which i think i have fixed. While i was doing some Googling this morning came across this site with the following quote.

Quote from Thoughbreaddiesel.com

Diesel fuel contains varying degrees of entrained air in the form of foam on the surface or suspended in the bulk fluid as tiny bubbles. Additionally, fuel is driven into the fuel pump by atmospheric pressure, which is usually only enough pressure flow to fill the pump at idle speeds. Consequently, at higher operating RPM’s, the stock pump cavitates producing vapor.

Air and vapor are compressible. The presence of air/vapor in the fuel injector delays the pressure build-up. This delays the injection, resulting in Retarded Injection Timing.

Retarded injection timing in a diesel, just like bad spark plugs in a gasoline engine, causes lost power, poor fuel mileage, and an increase in exhaust emissions. Retarded Injection Timing caused by air/vapor is the primary source of the rough idle, lost power, increased fuel consumption and excessive exhaust emissions of the diesel engine.

Air/vapor in the injector can also cause permanent damage in the form of galling and pitting of the barrel/plunger assembly and tip erosion.

The conventional vacuum feed fuel supply system does nothing to remove entrained air from the fuel. In fact, it only makes things worse. As the filter plugs with use, the already inadequate fuel flow to the engine is further reduced, increasing cavitation and retarding injection timing even more.
End of quote.

Makes you think that all diesels should have an air/fuel filtering system because the excess fuel from pressure regulator is in constant flow back to the tank creating more air in the system.
So I started thinking about a simple filter system using another filter with glass water bowl and lift pump.

Basic idea is to fit a 12v diaphram lift pump after the stock filter and then to another water separator filter upside down ( glass bowl on top ).
From the drain on the glass bowl on the second filter, fitting a nonreturn valve and line "T"ed into the fuel return line to tank.
This in theroy would help prime the stock filter after a new cartridge was fitted by lifting fuel through it, this would have the added benofit of not emulsifying the air into the first filter if it were before it, may not be a problem with this setup. Any air drawn up through the first filter would then be pushed through the second filter by the pump, where the tiny bobbles would coalize into large bobbles on the filter medium and float to the top of the glass bowl where they would exit through the nonreturn valve, maybe a relife type nonreturn valve to control pressure to the injector pump, not sure what flow rate or pressure to use.
With the pump between filters, the first filter would always be purged of air and filter media would be in full contact with the fuel. If the pump was before the stock filter, any air would be trapped in it untill it is bled out by primming pump.


Your thoughts and ideas welcome.

Regards
Petah

There are products out there solving this problem you might want to check out.

One that the Cummins crowd (and OTR rigs) like is the F.A.S.S. (http://www.fassride.com/)

It has a a pump that could power your jet ski, 2 micron filters, and an air separator.

Probably peels potatoes too... ; ' ) Seriously tho, they've a great reputation if you want to go all out.

Most of us have pretty good results with either an in-tank fuel pump (from the Dodge RAM trucks w/Cummins) or in-line just ahead of the tank. The tank/line fittings allow the stock configuration to suck air in where they join - I think they were originally intended for pressurized (gas/in-tank pump) systems and not-so-much for the vacuum that the stock CRD creates by pulling from the Bosch pump on the engine.

Mark

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2005 Liberty CRD
2004.5 Cummins 5.9L TD, F1s, NV5600 6-speed in a '93 GMC Suburban

G'day msilbernagel
That's the sort of unit same as AirDog that got me thinking about the air in our systems, and a cheaper way of getting rid of some of it.

From the quote it's fesable that air in the form of micro bobbles could be circulating in a closed system, especialy if only a small amount of fuel is in the tank and the air can't foam out to the surface.
The quote was from www.thoughbreaddiesel.com/airdog/original.htm bottom of the page.
So could this be robbing us of power and economy?

Regards
Petah

_________________
2002 KJ 2.5Lt CRD minor mods sofar.
My own design air/fuel filter setup.
2" spring lift, Snorkel, Rooftop camping setup.
And some mods of thermostat and fan shroud.
More to come as need arises.

When I installed my lift pump I also connected the fuel filter bleed port to the fuel return line through a check valve with a low pressure break point. The one I used broke at one pound of pressure. My lift pump is supposed to deliver about 4 to 7 lbs of pressure so if theory holds I should have fuel returning through the filter all the time to the fuel tank through the bleed port and maintain a 1 lb pressure feeding the fuel pump. Does not necessarily guarantee the diesel is degassed but will prevent any collection of air at the fuel head. The fuel pump should not cavitate and the only air reaching the injectors should be in the form of micro bubbles entrapped in the fuel.

No, I have not put pressure gauges on the fuel feed line or the return line to test the actual operating pressures, but the setup has been operating without a problem since it was installed. I may use up this first fuel filter faster than normal because I am circulating fuel all the time at some low volume but I have clocked several thousand miles with no issue yet.

_________________
Stone White 2005 KJ Limited CRD.
EHS, ORM, Fixed Flex Fan done.
Does EXACTLY what I expected pulling my 20 ft bass boat, chasing reds up and down the beach at North Padre Island.

G'day turbobill
Now that is even simpler and cheaper, I like it.
If we could get a definative answer about the micro bobbles effecting the injectors and timing, then this will be the way i will go.
Thanks
turbobill
Regards
Peter

_________________
2002 KJ 2.5Lt CRD minor mods sofar.
My own design air/fuel filter setup.
2" spring lift, Snorkel, Rooftop camping setup.
And some mods of thermostat and fan shroud.
More to come as need arises.

Okay, I'll wade into the water. FWIW Peter, I know of Thoroughbred Diesel and I know of Air Dog. BOTH are top shelf.

Basically the short answer to "Will the Air Dog help?" is: it depends! Not to be smart or anything, but it is relative. Yes, there is no question that you want to have a solid supply of diesel fuel to the injection pump, i.e. sans air, water and particulate. The Air Dog II can filter fuel of these three items, with particulate down to either 10 microns or 2, your choice-personally I would go for the 10 micron. There is no question that our mongrels would have a positive response to a better supply of fuel. It has already been shown to have a positive response with the install of some variety of the lift pump of your choice.

I have wanted to install an Air Dog II myself. The question is that of packaging on the vehicle. The footprint for the Air Dog is not small. You should mount it vertically and as close to the tank as possible. Remember, pumps push much more so that pull the fluid in question. My fear is that the filters will hang down and catch every stray pebble you encounter.

I have a Raptor lift pump (same company as the Air Dog) that I will be installing at some near point in the future. It is for a Chevrolet Duramax 6.6 Liter truck applicaton and it set to 8 PSI. If you should choose the Air Dog, look to this same application due to the PSI setting. Anything higher and I'm afraid that you will overwhelm the fuel system. While it may not have all of the advantages of the Air Dog, I believe that it will install with much less of a headache than the Air Dog and give you some advantages that you are seeking.

Now, with all of that said, IF you find a good way to mount the Air Dog vertically on our tractors, then by all means post the pics mate and I'm glad to copy and paste! Hope this helps.

Hoosier CRD

_________________
FWIW,
Hoosier CRD

#1 Liberty: '05 CRD Limited Stone White
(SOLD Dec. 2013)
#2 Liberty: ???
"Why guess when you can know?"- Carroll Smith

G'day Hoosier CRD
I'm not looking at fitting and AirDog or the like, they are just too expensive and bulky.
Just want a cheap way to remove some of those micro bobbles from the system and maybe add some reliability, can't do any harm even it didn't work. At the very least i would have a second filter.

Thinking about it a bit more and what i've read, a pump as close as posible to the bottom of the tank would be better than between the filters, as in my first thought. Less chance of emulsifing the bobbles further into the fuel due to having a flooded suction into the pump. A pump above the fuel could posibly cause cavitation and also more micro bobbles into the system.

Regards
Petah

_________________
2002 KJ 2.5Lt CRD minor mods sofar.
My own design air/fuel filter setup.
2" spring lift, Snorkel, Rooftop camping setup.
And some mods of thermostat and fan shroud.
More to come as need arises.

I really like the way this setup sounds, simple and effective, I would love to see a pic, and possibly know what kind (brand) of check valve you have.

_________________
2005 Jeep Liberty CRD - GDE Eco Tune - OME Lift - Cooper Discoverer AT3's 245/75R16

Something that may not be pointed out well on the internet with regards to the Air Dog II is that there is also a long suction tube that is incorporated. This tube is installed in the removable sump that is positioned at the top of the fuel tank. It draws fuel from the very bottom of the tank and therefore its opening is almost always covered with fuel. It would only be partially uncovered if you were say down to 1/8 of a tank or the like. The sump should have fuel in it most all of the time. It is always receiving returned fuel from either the fuel rail or from the Air Dog II itself. To be clear, with the Air Dog II, there would now be two (2) return lines going back to the tank.

One thing that a fuel injection system does not tolerate is large gaps of air in the system. If things start to get burpy, you had better be looking for a filling station. I do concede that the Air Dog is bulky though. Fitting one on a Liberty/etc. is not an easy task.

FWIW.

Hoosier CRD

_________________
FWIW,
Hoosier CRD

#1 Liberty: '05 CRD Limited Stone White
(SOLD Dec. 2013)
#2 Liberty: ???
"Why guess when you can know?"- Carroll Smith

I can understand large gaps of air being a major problem, but what about the small bobbles that are going through the system all the time.

To help me visulise it.
I can get a jar half full of diesel and shake it.
Now that is going on in the fuel tank if i'm not mistaken.

Now this is the part that I am assuming, and please correct me.

If the fuel pump has picked up some of those bobbles from the fuel tank and sent them through the injector pump and injector bypass ect. Would they not be more emusified into the fuel and then dumped back into the fuel tank ready to do the trip again.

Air is compressible, surely it must have some efect on timing, maybe not as much with common rail. I don't know, thats why i'm here.
From my experiance starting a couple of weeks ago when i changed the original fuel filter 9 years old, I have only had it for 12 months and my first diesel. I noticed an improvement in idling for a short time and then air started sucking in through the priming cap which i have fixed with an 0 ring.

I'm going with my gut feeling here and have started by fabricating a bracket and fitting another filter to see if any air accumulates in the bowl after a few days. I will fit a pump also as close to the tank as possible in any case, later.

Regards
Peter

_________________
2002 KJ 2.5Lt CRD minor mods sofar.
My own design air/fuel filter setup.
2" spring lift, Snorkel, Rooftop camping setup.
And some mods of thermostat and fan shroud.
More to come as need arises.

Hi Peter,

Glad to be of help. To affirm your thoughts on air in the fuel, yes it does cause a problem. In fact many problems. Mainly, entrained air in diesel fuel causes accelerated wear on the injection pump and injectors. It's called cavitation erosion. Many of the internal parts of an injection pump and injector are hardened. Especially in current production engines that are used here in the states. Diesel fuel acts as a lubricant to these parts. Specifically, it is the sulpher that is the lubricant. Due to our lovely EPA (Environmental Protection Agency) diesel fuel can now only have 15 ppm of sulpher. Previously the level was 500 ppm. If I remember correctly, there was a time in the not too distant past where the sulpher contect was 1500ppm! The hardening of the parts slows the wear. The entrained air, which has always been present, was a main source of wear prior to the drop in sulpher content. That and just regular use of the engine.

Performance is compromised due to the air in the system taking the place of fuel. As parts wear, performance is also compromised. The AirDog can at least give the engine (injection pump and injectors) a pure supply of fuel. Along with eliminating the entrained air, particulate and water vapor is also eliminated.

I can't find a better body of evidence than this video from You Tube.
http://www.youtube.com/watch?v=ujokaEkF8Z0

This is the demo of the AirDog that you would see at a trade show. The narrator is Mr. Charlie Ekstam, the inventor of the AirDog. This video clearly shows how entrained air flows through the fuel system and how the AirDog eliminates it.

I have said many,many times that if you have a diesel engine, you either have an AirDog or you need one. In the case of the Liberty CRD, I guess we need to build an extra room on the side of it to house the thing!

Hope this helps.
Hoosier CRD

P.S. The quote you used in your last message was from me. I'm not sure who "Greaser" is though.

_________________
FWIW,
Hoosier CRD

#1 Liberty: '05 CRD Limited Stone White
(SOLD Dec. 2013)
#2 Liberty: ???
"Why guess when you can know?"- Carroll Smith

G'day Hoosier CRD

Don't know how Greaser got the "quote" must be a bug in the system.

Great video, that just makes it so clear. This is what i have been imagining happening in the tank.
The return line size is a little exaggerated, but the principle to me seems wright.
You seem to know a bit about the AirDog, have you used one.
If i could afford one i would, but as you pointed out, it's too big for our KJs.

I'll have the install of my filter finished today. Will let you know what i find.

Regards
Petah

_________________
2002 KJ 2.5Lt CRD minor mods sofar.
My own design air/fuel filter setup.
2" spring lift, Snorkel, Rooftop camping setup.
And some mods of thermostat and fan shroud.
More to come as need arises.

See viewtopic.php?f=5&t=24527&hilit=automatic for BlackLibertyCrd's bleeder mod with pictures. Nice idea but I've not tried it as the 2gen CRD fuel filter head solved my air in fuel problems. If the problem comes back I have a Facet lift pump on the shelf and will install it; maybe with this mod.

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Sold to LOST member my 05 Ltd, GDE Stg II turbo + TCM tune, SunCoast TC w. Transgo kit, Steiger window regulators, Samcos, Fumoto valve, 2nd gen filter head with Lub. Spec. bleeder, Hayden clutch & 11 blade fan, inverted spare, P-1 battery, BF Goodrich Long Trail TAs, Etecno1 glow plugs, timing belt at 50K miles/8 yrs

Update
Filter is in and working great, bad news is i have an air leak somewhere up stream of the filters.
It's easy to see the air bobbles rising up from the filter cartridge into the glass bowl. I thought it was just air trapped in the cartridge at first, but after bleeding it out three times i'm sure it's coming from the fittings near or in the tank.

It now confirms to me that i have had an air leak getting worse for the whole time i have owned the Jeep ( over 12 months ).
Funny how you think things are normal when you don't know different.

When i started it for the first time after bleeding it. It sounded different, my wife also noticed it. Idels much smoother, and sounds so different to what we were both used to.

There's definitely no visible air bobbles getting past the filter. I have only ideled it to 2000 rpm. Sofar Very happy.

Question: Are there any joints on top of the tank that could leak air?
Don't want to drop the tank, but might have to if the leaks on top.
Theres a plastic push fit conection about 6 inches in front of the tank, thats where i'll be fitting the pump.

Haven't taken it for a drive yet as i have'n fitted the lift pump. Thats going in tomorrow, I'll post some pics of the bracket and filter setup aswell.


Thanks papaindigo for the link to BlackLibertyCRD lift pump setup.
Has some pointers for wiring the pump, not too keen on pump placement, but it is easy to get to.

Regards
Petah

_________________
2002 KJ 2.5Lt CRD minor mods sofar.
My own design air/fuel filter setup.
2" spring lift, Snorkel, Rooftop camping setup.
And some mods of thermostat and fan shroud.
More to come as need arises.

Petah,

Sorry, that is where my knowledge ends, unfortunately. I have not directly used an AirDog myself. My KJ is the first diesel-powered vehicle that I have owned. However, I have seen several in action and have spoken with the owners of the trucks. They, almost to a person, have stated that they have noticed a nice difference in how their truck performs. Secondly, I have a performance-oriented technician in the shop where I work who swears by the AirDog and none other (!) for this type of part for a diesel truck. These instances combined with seeing the demo (up close in a meeting) that I showed you in the video convinces me that if I can shoe horn an AirDog underneath our KJ mongrels, mine is named Thumper btw, then that is precisely what I will do, and he'll run all the better for it. I realize that I have stated that I have a Raptor lift pump. This thread has re-inspired me to give the AirDog a go once again and this time make it stick!

FWIW,

Hoosier CRD

_________________
FWIW,
Hoosier CRD

#1 Liberty: '05 CRD Limited Stone White
(SOLD Dec. 2013)
#2 Liberty: ???
"Why guess when you can know?"- Carroll Smith

The fuel line fittings that connect the lines to the top of the tank are made to be pressurized, but unless you have a lift pump in the tank, they will likely be under vacuum, for which they are not designed. Others have replaced the fittings with regular fuel line and hose clamps.

_________________
2006 Liberty CRD Limited

Provent @ 43,000 km
SEGR in progress
SAMCO Sport hoses @ 48500 km
Goodyear Wrangler Duratrac LT225/75R16

Thanks for that.
So i wont know if i have a leak on top of the tank, untill i fit my lift pump and use up the 40 odd litres to make it easier to drop out.
It's not drivable atm till i finish the return line valve and pump install.

Regards
Peter

_________________
2002 KJ 2.5Lt CRD minor mods sofar.
My own design air/fuel filter setup.
2" spring lift, Snorkel, Rooftop camping setup.
And some mods of thermostat and fan shroud.
More to come as need arises.

The best solution for fuel aeration: viewtopic.php?f=98&t=37868

All the expressed hysteria about putting pressure on the inlet side of the CP3 is that Hysteria.
Some CRD owners have gone as high as 20PSI on the inlet side of the CP3 with only positive effects.
Using the SUCK DAH Fuel out of the tank design was pure Bean Counter Engineering to cut costs.
The other easy upgrade you can do for your '02 is to put the biggest 2 micron Racor fuel filter you can screw on. My '06 used a piece of crap filter that I made an adapter to use the 2 micron Raycor filter. Also I made an adapter to fit the WIF sensor. Others have converted their '05 & '06 CRDs to Raycor filters. Another member who has an extended warranty, put a 2 micron Cat filter down stream of the crap filter he needs to keep on for his warranty, best of both for him.



If you feel a small tremor in West Minster Abby, it is Sir Isac Newton rolling over in his grave from another incidence of Bean Counter Engineering.

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2006 Pearl Green CRD
Magnaflow 2 1/2" Cat Back
KJ Extra Leg Room Brackets, Carter Lift Pump, V6 Airbox, ORM
Fuel cooler, Oil Separator, Progard 7
Gauges EGT Boost Trans Temp Oil Pres, Michelin LXT AT2 245 70 R16
7,000# Draw Tight hitch, PML EX Deep Trans Pan
Centrifuge, SunCoast, Transgo, RAM TCM, InMotion Stage 2
Wife's 99 TDI VW Beetle

FYI - this one involved some custom parts - but it was a clean install
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?p=252515#p252515

_________________
2005 CRD
stuff
Skeptic quod gratis asseritur, gratis negatur

Thank you warp2diesel and ATXKJ for those links, great info.
They are way more complicated installs than mine.

I'll post some pics tonight.
One thing, it is definitely running smother and quieter, even my next door neibour commented that it sounded quieter. I can only put that down to a lot of air being socked through that plastic push fit connection near the tank, that I cut out and replaced with the lift pump.
Still haven't driven it. It's up on jack stands.

Having a problem with a faulty Facet FEP12SV pump, will not produce more than 250ml/min and closed valve pressure of 2.5psi. Supplier is getting me a different brand pump.

Biohazard KJ CRD's install used the power from terminal or relay 5 in his write up. I don't have that relay in my fuse box shown in the pic. Where's the next best place to get power. I don't want it to run on accessory, only while engine is running.

Regards
Peter

_________________
2002 KJ 2.5Lt CRD minor mods sofar.
My own design air/fuel filter setup.
2" spring lift, Snorkel, Rooftop camping setup.
And some mods of thermostat and fan shroud.
More to come as need arises.