View Full Version : I've got gas
FirstDiesel
04-06-2003, 11:43
Air actually!!
I bled my Mega filter again today. Pumped up the filter and opened the bleeder. Air. Did this 4 or 5 times before I got diesel.
This is a ton of air. I have had the filter on the truck about 200 miles now. I have bled it 4 or 5 times with the same results as above. Seems to me by now I should have removed any trapped air so there must be air entering the system somewhere. I have no starting or driving issues but am not happy with the thought of this amount of air getting into my system.
Jk, anything yet about a solution??
FirstDiesel,
Will any other (2 micron) Baldwin filter or CAT filter fit JK's
filter head? That might be a way to see if it is only
the Baldwin MEGA medium that's actually capturing the
disolved air in our fuel.
[ 04-06-2003: Message edited by: 56Nomad ]</p>
FirstDiesel
04-06-2003, 12:36
I'm not sure what other filters will fit. I guess J.K. will have to tell us that. I'm having a hard time beleiving it is the filter medium capturing air though. The reason is if it were shouldn't everyone have the same air problem?? That's not happening. Only some of us are lucky enough to have the problem.
I'm of the mind set that there is an air leak somewhere in the system and the filter just is allowing it to accumulate.
Here's something for you think about FirstDiesel, did you ever think to install one of those automatic air purge units that are installed on home based boiler systems.
It allows trapped air to escape without losing water so you don't get the annoying bump and bubble going through your baseboard heating pipes.
If I remember correctly the cost is under ten bucks for one. I just don't know about how diesel fuel will affect it (Brass and Neoprene)?
Might be worth a try just the same.
Good luck
hickcox,
Great idea, but where is there any space to install it.
There is not much room at all under that airbox after
you put your filter assembly in.
56Nomad It's only about the size of a roll of quarters you just have to tee it off in line.
Like I said it might be a good idea to test it's compatability with diesel fuel first (probably fine).
Next question...... will it work with vacuum?
biglouieky
04-06-2003, 14:46
Suction/Vacuum Side Fuel Filters
Suction-side fuel filters are located upstream from the pump. The fuel flows by vacuum through the filter as opposed to those located downstream from the pump where the fuel is forced, under pressure, through the filter.
Problems associated with suction/vacuum side fuel filters are usually not obvious. The most serious problem to consider is loss of vacuum. Vacuum loss caused by air leaks will result in loss of engine performance.
Air being sucked into the fuel system could result in lower fuel delivery. Power and performance will be affected by these conditions. Locating the air leaks in the fuel system is normally very difficult. The common conclusion is that there is a suction leak around the fuel filter.
One observation made in the field is the fact that during servicing of a suction-side fuel filter it is only partially full when removed.
Most suction-side fuel filters will be partially filled with fuel when removed from an engine. It may also seem that full utilization of the media is not being obtained. The air-vapor cavity or air entrapment is caused by the surface tension of the fuel. It can also be referred to as the passage resistance of wetted filter media to allow air or vapor to pass through. The magnitude of this resistance to vapor passage is related to paper pore size and fuel surface tension. By decreasing the pore size, one will increase resistance to vapor passage. An increase in surface tension will also result in an increase in resistance to vapor passage. Once the media pores are wetted with fuel, these pores will not allow the passage of air until the vacuum on the clean side is sufficiently greater than the vacuum on the dirty side of the filter. This vacuum differential increase will break the surface tension of the fluid bridging the pores.
The only time that the air will pass through the media is when a differential vacuum across the filter overcomes the surface tension. In actual engine installations of suction-side filters, when the primer or transfer pump is activated, a differential vacuum across the media is created. The differential vacuum is large enough to overcome the surface tension and allow the passage of air and/or fuel through the media. As the media is wetted, the air-vapor barrier is formed and so any new air vapor generated will be blocked from passing through the media.
With the fuel system completely sealed and assumed leak proof, then one may ask, how is the air generated and where does it come from? The source of air vapor is the diesel fuel itself. Similar to water, diesel fuel contains a certain amount of dissolved air, depending upon the fuel temperature, pressure on the fuel, specific gravity and the amount of aeration to which the fuel has been subjected. Increasing the fuel temperature or a fuel pressure reduction will release the air. The amount of air released is dependent upon the degree of the air saturation of the fuel and the magnitude of temperature increase and pressure reduction.
In actual laboratory experiments duplicating a filter as installed on an engine, it has been proven that the filter will always be full on the clean side and air-vapor is present on the dirty side only. Therefore, there is always sufficient amounts of fuel leaving the filter. The reason that the filter appears partially full when removed from the engine is because as the seal between the filter and the mounting base is broken, the vacuum differential across the cartridge is also broken and the fuel level on the clean side and the dirty side of the cartridge are instantly equalized, thus resulting in a filter that appears to have had the same fuel level on both sides of the cartridge when under operation.
There are, however, instances that some filters upon removal from the engine do appear to be full of fuel. The reasons could be any of the following:
1. There are voids in the seal between the element and the end caps.
2. The element does not seal properly in the filter or housing.
When these conditions exist, a filter bypass condition exists and a filter may then be full of fuel when it is removed.
Remember that the air passage resistance is related to paper pore size. Therefore, a bypass in a filter will represent a large pore size. Hence, easier vapor passage.
Note of Caution: If a suction-side fuel filter is full of fuel, do not automatically assume that the filter is of an inferior quality. There are other reasons beyond the scope of this publication that contribute to this effect and may not necessarily mean filter bypass.
--------------------------------------------------------------------------------
Back To Technical Service Bulletin Index
biglouieky,
Thanks for the fine explanation. I knew that a filter on the suction side can be only partially full. I just didn't know how to explain why and didn't want to make a fool of myself. Noticed this several years ago on one of my 5.7 diesels. I installed a pre-filter on it and everytime I changed filters they would be low on fuel. I asked someone about it that had a lot more knowledge than me, and he said he didn't know why either, but that this was the case on a lot of pre-filters. tpitt
My feelings, at this point, are leaning towards "natural occurrence" as the air in the fuel is seperating and rising to the top. The design of my system will allow pressurization of the filter housing, and the dirty side bleeder will allow evacuation of most any air that is free. From this point, one must figure out WHERE this air is coming from. It could be from a vacuum leak, OR just from air suspended in the fuel releasing.
An automatic air bleed is only practical in a pressurized system.
So I guess the next step is to install a clear hose setup and see if there is any visible air coming from the OE unit during engine operation, AND when pumping the primer.
From there, I guess it will take an A/C vacuum pump, a refirgerant sniffer on the exhaust, and wafting a bit of a detectable gas at the seams/joints on the OE filter unit. This, of course, is best done as an off the truck operation. One could further check the system with the same procedure by plugging the pick up tube in the tank. Not sure WHEN I will get time to do this...
Truth of the matter is, I'm not too concerned, as regardless of WHERE the air is coming from, catching it is a GOOD thing. I have run 600 miles since bleeding mine, and have had no trouble. I even ran it down to the low fuel light. All it takes is a simple purging to remove any accumulated air.
One thing that DOES seem consistent in all of this, is that after installation, whether a placebo affect, or not, it is most always reported that the truck runs smoother. FWIW, at least one reporting party has an MD in his title...
FYI... Here is a link to the info in biglouieky's post.
http://www.baldwinfilter.com/engineer/tsb_94-6r.html
smile.gif
FirstDiesel
04-07-2003, 14:41
JK
I've asked this question before but with the air I'm seeing in my filter I'm wondering if this is my problem.
My truck runs well, starts fine, but when I idle at a traffic light the truck will idle a little rough, intermitantly. No real change in RPM's or anything like that it just shakes a little.
Could this be the air in the fuel line?? I'm not sure if it's still doing it since I added the Mega unit. Will bleed it and then pay careful attention to the idle. I'd do it now except I got home and found my wife drove the truck to work today instead of her sportscar. :eek:
I haven't had it on long enough to totally bleed the system, but plan to go for a ride momentarily.
I have a clear hose between the EDU and the OE filter housing. Each push of the primer pump will yield a group of several air bubbles when the primer "gulps" fuel from the EDU. The EDU is the high point of the system so it is natural for air to collect here.
After I have some more run time to ensure that it should be bled, I'll recheck.
Once again, I think that what we are doing is "stripping" this air from the fuel and accumulating it in the Mega filter. We are doing our engines a service by removing this air. Now to find the point of entry...
How are you guys bleeding the pre OEM under the air filter mount ??? Removing the wheel well liner, for access ?? Good grief the night mare that could be .... I'm really starting to diss like that mounting position entirely....
Has anyone entertained the possibility of getting a 2 micron to fit the stock mount ?? Then run a stone catcher 15 micron at the tank -frame rail ?? I don't need an idiot light for water sensor.... A clear bowl would suit my needs under the hood..... Would seem like a pretty clean setup if you ask me.....
Not a possibility ??
MAC
FirstDiesel
04-07-2003, 17:30
Actually Mac, it's easy.
The bleeder is in front of the airbox and a long straight blade screwdriver will reach from the top. Or what I've been doing is removing the headlight and put a rag aon the filter top and then open the bleeder.
Bleeding it is easy. My concern is where the damn air comes from!!!
After several miles of driving, I see occasional bubbles about the size of a pin head traveling in the fuel. This is at idle.
Then when I push the primer, I get a small amount of bubbles initially, until I get to around pump 5-10 (I didn't really think to count) when I get large schools of bubbles. This would likely be, by volume, one of the push lock fittings. I'm hoping that the Snap-On man has the line disconnect tool on the truck with him tomorrow so I can pop them open and fill with dielectric grease and retest...
chuntag95
04-07-2003, 19:42
FirstDiesel,
My truck was giving the same symptoms as your is (but my filter isn't here yet). Two injectors were replaced and it seems to be much quieter and smoother. I am starting to get a little of it back intermittantly. I think one injector might be going flaky. Worst you can do is take it in and have them check out the balance and pilot injection.
Chris
John,
I also mentioned my concern about those push lock connectors in my first post on air in fuel filters. That will be the next thing I will be checking if the resealing of the OEM filter gasket proves to not help. Will probably remove the OEM to run a vac.test and then a pressure test while submerged in liquid. from there I will work my way back to the tank by section. I plan on persueing this 12/7 when I return home Wed. Maybe you should have a reward for the 1st to find the soarce of entry. :D :D A couple Extra elements for example. :D :D Hint Hint
Mac,
Bleeding the filter is as easy as pie.
:D
[ 04-07-2003: Message edited by: a bear ]</p>
I've got a Mityvac kit coming from Snappy, but since it is not Snappy brand, it may take a while.
It is hard to tell which push lock it would be, but it seems to take about 10 pumps till it gets there in a NON running engine. Naturally, the first connector above the drivers valve cover is first on the elimination list.
Point of entry #1 appears to be eliminated. The pusk lock fitting above the driver valve cover has been disassembled, packed with dielectric grease and reassembled. I no longer get large bursts of air drawn through my hose when the primer refills. I still see some tiny bubbles flowing through, but I'll wait to pass judgement until I have some more run time. That should happen this aft hopefully.
If these tiny bubbles persist, I'll try the next fittings going rearward to the tank. In all liklihood, I'll end up doing them all eventually, but I'd like to take one step at a time so I can see which ones are indeed leaking.
chuntag95
04-08-2003, 14:09
John,
Did you tighten the banjo fittings or find any of them loose?
Chris
John,
Really don't like the push lock fittings. Does it look like the grease will work long term. Was thinking of using another fitting or hose if they were leaking.
[ 04-08-2003: Message edited by: a bear ]</p>
I'm really not sure that I have it completely sealed. I still see some bubbles, but it seems as if there are pockets of air trapped at various points. It takes a LONG time for this air to work out. It has diminished greatly since I reassembled, but I cannot really tell if it is still making or just purging.
I also did the connector behind the fuel cooler. I am assuming that is the last one? I did not look at the top of the tank.
I doubt that the dielectric grease will go anywhere.
I tightened both banjo fittings, but they only went a very little bit.
John,
What tool are you using to open the Quick Connect fuel line fittings? Is it the split collar type that slips inside the fitting and releases the connection? My Helms manual calls for a J44581. Do you think an equivalent tool might be available at an auto parts store? I would also like to try re-sealing these fittings. (I remember reading that some of the Ford guys have eliminated them on their trucks)
[ 04-08-2003: Message edited by: jbplock ]</p>
I got the Blue Point assortment from Snap-On today. These are plastic clip ons. The multi-sized scissors style by KD wouldn't get in there worth a darn so I went with the plastic ones.
Listed as AC line disconnect tool. Dunno how these lines are supposed to seal refrigerant :confused: I guess pressure is easier to seal than vacuum...
JK,
Found this in the snap on book.
PN. ACT1370 disconnect set
Would that happen to be it.
When I installed the Transfer Flow tank, I found a set of the fuel disconnect tools at Sear's for about $10. Made by Lisle Tools:
www.lislecorp.com/tools/catalog/general/index.htm
37000 AIR CONDITIONING / FUEL LINE DISCONNECT TOOL SET
Easily Disconnects Air Conditioning Lines and Quick Connect Fuel Lines.
Set of six tools which disconnect the spring lock couplings on Ford and Chrysler air conditioning line. Also works on fuel line quick connect couplings found on GM, Ford, and Chrysler. The 5/16" size fits on push lock connectors found on Ford radiators and transmission lines. Easy to use in confined spaces. Set includes six sizes: 5/16", 3/8", 1/2",5/8", 3/4" and 7/8".
37000 Air Conditioning/Fuel Line Disconnect Tool Set. Skin-packed. Shipping wt. 6 oz. Dealer Price $9.95
There is a pic of the tools at the first link in my sig in the Center Console/Transfer Flow album - the last pic I think, or check this link:
http://community.webshots.com/photo/59802499/59806992siCthJ
Kennedy and abear,
Looks like the Snap-on and Lisle are the same tool...except for the price :eek:
Kennedy,
GREAT idea with the clear hose!!! What type of hose did you use?
mdrag
I think mine was $14.95 or $17.95, but it sure beats going to the MALL!
I just used clear vinyl tubing.
Guys, Thanks for the info on the tool! Turns out that I have the same set as shown in Mdrags picture. I'll be re-sealing the QD's this weekend to see if I get less air. I may also use some Parker super-O lube on the OEM filter o-rings (per Tommy's suggestion). :D :D :D
[ 04-09-2003: Message edited by: jbplock ]</p>
Well, still no Mityvac. Friday hopefully. I'm going to give it a while to purge itself, but I'm thinking I'm still "making" air. I'm going to revisit the one by the tank as it seems a bit worse after opening that one up. The increased suction of the primer filling "draws" gobs of air into the clear hose feeding the OE unit.
I talked with a Tech who replaced a sending unit assy that was leaking. This one caused a /no start though.
Could be:
Banjo fittings at EDU
The EDU itself
Hose between banjo and hard line
2 different push lock fittings
Any line/hose on the way back...
I NEED that darn Mityvac...
Out of frustration, I decided to pull the banjo fittings on the EDU. They are sealed with steel washers with some form of teflon type coating. First thing I noticed was that the entire surface of these washers was "gritty" looking in the dampness of fuel. I wiped them, smeared on some dielectric grease and reinstalled. I also repacked the push lock fitting above the valve cover. I may look into copper washers also. These steel ones are bridged together for easy installation, but if a copper washer can seal brake fluid and most other injection systems...
I still a small get air during the first few pumps of the primer, but if I keep it up, I can get visibly clear fuel. I'm not sure if there are any tiny bubbles present as it is really tough to see. Previously, I would get continuous groups of bubbles. Now if I leave it idle, or off, I get some bubbles early on, but can get it to come clean. Not sure, but I'm kinda guessing that it's the EDU banjos that are leaking on mine. Of course, I broke a cardinal rule by doing 2 mods at once, but frustration got the better of me!
It could still be that I have a minute leak that is finely "carbonating" my fuel and when it enters the EDU it has a chance to collect. There's also the chance of a pinhole in the welding on the EDU...
John,
Another thing I will be considering is how close the fuel return line discharges to the fuel suction. Will start with all this in the AM.
chuntag95
04-09-2003, 20:48
Tommy,
Are you thinking the return is "mixing" air into the fuel with turbulant flow?
Chris,
I think it's possible. Air could be entering the fuel line slowly then accumulating in the high spots. Both lines appear to be entering the tank near each other. I'm not sure on the return line depth or orientation once in the tank though. It will be the last item to check due to the added difficulty. Possibly dropping the tank a few inches. I think things will go quick with John's clear hose idea. Shouldn't have to wait between checks.
[ 04-09-2003: Message edited by: a bear ]</p>
chuntag95
04-10-2003, 09:46
Tommy,
I heard from a friend of mine who had to replace and in tank pump that it is easier to take the bed off then drop the tank. :eek: Neither sound like much fun.
In absentia of a vacuum pump I snapped a hose pinch plier on the hose at the drivers valve cover. This yielded an eventual 12" hg draw at 1100RPM. What I found was more bubbles. In fact, when I released it, I had a TON of super tiny bubbles, much like a "fog" look.
pinehill
04-10-2003, 12:11
JK,
The "ton of super tiny bubbles...", looking like a fog, are most probably the air which is dissolved in the fuel being released by the relatively high vacuum you applied. It might make sense to restrict your testing to the maximum vacuum levels you recommend as the point where filters are to be changed, ie, 5-7 inches. No ammount of leak fixing will eliminate this fuel outgassing under high vacuum. Many years ago, I had the opportunity to observe many liquids, under differing conditions, in a vacuum chamber, and at about a half atmosphere, just about anything will outgas.
Dunno what I'll find, but my next attempt will be to push out the fuel, put a mild pressure on the system and do the soapy water check...
Pinehill,
Do you REALLY think that there is that much air in diesel? Could well be, but after talking to a technician who had troubleshot a Dmax air issue and found it to be the sending unit, he described the same type of fog...
pinehill
04-10-2003, 13:19
John,
As I've said before, I really don't know to what extent air dissolves in diesel fuel. My *guess* is that if ambient temperatures are relatively low, like below 60*F, and if the truck has recently been driven with a partially full tank (sloshing), there could be significant dissolved air. When this air- laden fuel reaches hot engine parts, like the injector electronic drivers, it will more readily outgas under a vacuum.
I'm beginning to think that we have a combination of both leaks and outgassing going on here. Either way, stripping the air is definitely not a bad thing...
Lone Eagle
04-10-2003, 19:22
John, At 12 inches I would suspect you are vaporising the fuel and it is going to cause cavitation. Later! Lone Eagle
Yeah I wasn't shooting for 12", but it's tough to regulate with a pinch plier. What really surprised me was how hard it was, to make enough restriction to get the vacuum up! Aside from possible "outgassing" and vac leak elimination, I really see no need for a lift pump. There just isn't a ton of flow in this thing, just STEADY flow...
On a related note, I got my proto restriction gauge set up.
chuntag95
04-11-2003, 07:42
John,
What's the baseline on your Proto restriction gauge? Is it pretty steady regardless of throttle?
I need a bit more time to get familiar with it. It zeros kinda goofy, which I believe has to do with atmospheric pressure. I've got a liquid filled gauge that is connected to a quick coupler via a 90
Eliminated the following as a soarce of air in fuel.
1. Outgassing (Pressure drop and temp increase not favorable)
2. Mega filter and associated hoses and fittings.
3. OEM filter gaskets,drain,bleeder,primer and all hoses and fittings.
4. EDU coils banjo fittings and hoses.
5. Shrader valve fittings and lines.
6. Airation of fuel from return line.
What remains to be checked.
1. All push lock fittings from drivers side valve cover back to tank. Associated hoses.
2. Fuel sending unit. Last to check due to lowering of tank.
At this point there are definite signs of air entering system at one or more of the items not checked. I plan on resuming checks Sunday AM.
;)
CntrlCalDmax
04-11-2003, 16:14
a bear,
Can you explain how you checked the items you eliminated? That's quite a bit of ground to cover, did you discover short cuts to eliminating those as potential leaks?
Leo
Tommy,
Excellent work! Thanks! I too am curious how you did your tests.
After talking to Tommy, he basically attached hose to the push lock by the valve cover and drew his fuel from a can. No more air...
Lone Eagle
04-11-2003, 19:02
I think adding a lift pump is totally unnecessary and would open up a can of worms. I can count on one hand the industrial systems I've seen with a charging pump. The data that came with my Racor said the pressure drop is .05 @ 30 PSI. I don't know how much it would add to the total suction head. I suspect not very much. Later! Lone Eagle ;)
I was under my truck today and noticed a drop of fuel hanging from my drain valve. I wiped it clean and several miles later it was wet again. I have only drained it once and the drain was closed tight. I am not impressed with the quality of the drain, or the rest of the filter and primer for that matter.
I figure if fuel is leaking out, air can leak in. My JK unit has gas too. I bleed it every 300 miles or so and it bleeds air every time, taking several pumps to evacuate.
Any thoughts on this, and where do I get another drain valve? If you ask me, the whole OE filter system is cheesy. SPICER
Leo & Bill,
This will test everything from the drivers side valve cover to the filters.
First installed a 1/2" clear vinyl hose between the EDU and OEM filter to monitor for air per JK. Primed, cranked and got air after about 4-5 pumps on the primer. Repeated a few times and got the same amt of bubbles each time. SD engine and disconnected last pushlock fitting on return line after fuel cooler. Installed a few feet of 5/16" ID clear vinyl hose from return fitting and routed to a clean 1 gal. jug. Cranked engine and started filling jug with returns. After filling jug SD engine and disconnected pushlock fitting on suction line above drivers side valve cover. Hooked up 7/16 ID clear vinyl to this fitting and routed the other end to the jug for suction. Pumped most of air out of hose with primer and cranked engine. Finished working air out with primer pump while running. After working air out got a solid stream of air FREE fuel in hose from EDU to OEM filter. Restricted flow on suction hose to increase suction head. At this point realized the suction pump was a hell of a pump. Ran engine for a while through various RPM cycles and checked for air. NONE nothing but nice clear fuel. Put return hose to tank filler and allowed engine to pump remaining fuel in jug to the tank. SD engine and hooked the OEM connectors back up with O-lube. Recranked engine after priming and the normal amount of air prior to test returned.
At this point the air is W/O a doubt coming from either one of the last 2 pushlock connectors or the main suspect (sender unit)
Looks like history may repeat itself on that sender. JK stated these were a problem before.
Hope this helps.
Tommy,
Thanks for the detailed explanation! I’m anxious to hear what you discover with your sending unit. Do you (or John) know the failure mode of the senders that failed on other trucks? Is it a problem with how the unit seals to the tank or something internal? Since several of us have air, it’s beginning to look like this may be a “feature” of either the pushlock fittings or the sending unit. (I’m glad I have the Megafilter with it’s long clean-side nipple keeping this air from getting to the pump and injectors!). I’m tempted to just remove the suction side push-locks and replace them with hose clamps but I guess I’ll wait until you (and John) complete your tests. Thanks!!
smile.gif
Bill,
John informed me about previous sender failures. Won't know for sure how it's made untill I get there. One thing I have also noticed is the questionable sealing surface of the push lock fittings. It uses one small O-Ring and moves around alot. The last one on the tank has to seal on a molded tank nipple with a not so good sealing surface.
Will be returning tomorrow and hope to finish up checks. Ditto on the Mega filter.
I have heard of sending units "gassing" from White Truck, and Duramaxallitech.
Per White Truck, the orings for these quick connects are NOT available seperately. You must purchase the entire line section.
At this point, on abear's rig, I beleieve that he has eliminated the push lock at the valve cover by changing out the short hose and using clamps???
I'm off fo an appt this AM, but hope to mimic Abear's testing only by pulling my fuel from the push lock by the fuel cooler. I still have quite a bit of fuel in my tank to be dropping it.
I think at this point, I have a definite need to see how the sending unit and it's associated standpipes are configured...
Tommy/John,
I was just looking at the push-lock connectors near the fuel cooler on my truck. The return line connection has a lot of “float” to it but the feed line connection was firm. I also used a mirror to look at the top of the tank and there are two more push-locks that connect to what look like plastic nipples on top of the sender. Tommy, is this the molded connector you were referring to? There is also a middle nipple on the sender that has no connection (??) These sender connections would only to be accessible by dropping the tank (or raising the bed). If the push-locks are the source of the leak, it seems like one could just replace the whole push-lock feed line from the tank to hard line with a length of high quality hose and clamps.
Also, when looking at the sending unit R&R section of the Helms manual, the next page shows a frame mounted lift pump! This is in the 6.6L section, page 6-2896 of the 2003 manual (volume 3), and the title is “Fuel Pump Replacement (Cab/Chassis)”. Looks very similar to the 6.5 lift pump. Anyone know if the Cab/Chassis models come with this pump installed? and if so why ours don’t ?
BROKERS, (if you’re out there)
Since your trucks are the current benchmark for injector life and mileage, do yours have these lift pumps? Also did your mechanic eliminate the push-lock connectors?
smile.gif
[ 04-12-2003: Message edited by: jbplock ]</p>
Bill,
I believe the cab/chassis trucks come with dual fuel tanks and I think the fuel pump is used to transfer fuel from the aux tank to the main tank. Could be wrong,,, but I seem to remember reading this somewhere.
Alan
SoMnDMAX
04-12-2003, 11:32
Tommy, check your e-mail....
Matt
CntrlCalDmax
04-12-2003, 12:26
I had a real problem with air in the fuel. I had to bleed the system after every 150-170 miles or it wouldn't start. I believe my problem is a combination of vapor lock (out gassing) and leaks from the OEM filter.
In aircraft we have vapor lock problems due to the change in atmospheric pressure during climb. The cure is to turn on the boost pump, if one is available for the tank being used, or in some cases, bulletins have been issued to install aux pumps (lift pumps) to eliminate the problem (Cessna 340 & 414 aux tanks). Based on this I installed a lift pump similar to dpearl river's unit, on the frame just in front of the fuel tank and have driven just over 240 miles. I bled both the OEM and Mega filters and had no air. Pure clear fuel came from both bleeders. I'm not suggesting this is a cure-all for everyone's air problems, but I am very happy so far. I hope to have time soon to install a pressure gauge on the outlet of the lift pump to be sure it has enough volume and maintains a positive pressure at high RPM/Load.
The lift pump is also another 5 micron filter so now I have Pre - OEM - Post. I think I'll change the pre filter every 5K miles since it is so easy, the OEM every 20K and the Mega filter every 30K miles to start with.
I also installed a bypass around the lift pump just in case the pump fails. With a failed pump I can still run by opening the bypass valve which is installed on the outside of the frame and easy to get to. Pictures are posted. See sig.
technician
04-12-2003, 14:10
jbPlock,
You're correct on the chassis cab pump in tank. The pump is there to transfer fuel from aux tank to main tank which is where the pick up is. :D
pinehill
04-12-2003, 15:06
A while back, someone indicated that there could be problems in presenting a positive pressure (lift pump) to our positive displacement injector pump which normally operates with negative pressure upstream. Are these problems inherent to a setup like this, or would they be a result of fuel system monitors sensing an out-of-range condition of some kind?
If such problems *don't* really exist, it seems that, after taking care of gross air leaks at line couplers and other joints, the addition of a lift pump/gross filter near the tank would be the ideal solution to any air outgassing/fuel vaporization caused by vacuum and elevated temperatures in the engine compartment.
The success, to date, of those who have installed lift pumps would seem to indicate this. In addition, we would then have a fuel filtration system like that which gave Broker all those miles on his original injectors.
[ 04-12-2003: Message edited by: pinehill ]</p>
CntrlCalDmax
04-12-2003, 18:34
I am not an expert on pumps but have worked around many types of fluid pumps for years. Most pumps are designed to create a differential pressure between the inlet and the outlet or in the case of positive displacement pumps, move a specific amount of fluid per cycle. It seems to me that raising the inlet pressure by 6-7 psi would only affect seals that seal the fluid from the atmosphere, as this would be different than when pulling a vacuum. I don't believe the Dmax first stage pump could have a problem with this low positive pressure.
I have installed a gauge in the lift pump outlet and static, or at idle, it runs 7 psi. Full power, Hot Juice level 4, it drops to 3.5 psi. As long as the pressure remains positive, the lift pump has enough volume for the engine fuel flow requirements.
This positive pressure also eliminates any air leak problems. As long as the pressure in the fuel lines is greater than atmospheric, any leak will be fuel out rather than air in. I can not find any visible fuel leaks so far.
I have one question on the Stanadyne pump filter. Does anyone know if the filter has an internal bypass for a restricted filter or does the flow decrease when the filter becomes saturated with debris?
Bill,
The pushlocks do have some inward/outward movement. Some harder than others. The poly nipple on the tank is the one I was refering to. It has the raised seam lines typical of the moulding process. I can't see how the hard O-Ring on the push lock could give a reliable seal around this under vac. :confused:
All,
I will also be checking the sender as John mentioned. The leak could be either. I did eliminate the pushlock fitting above the valve cover and used hose/clamps insteaad. I feel a whole lot better with this for long time reliability under this vac service and intend to do the same at the tank.
Right now I feel confident that the leak repair/repairs will take care of the air problem.
I would definitely chech with Bosch before using a lift pump. Judging by the way this LP pump keeps prime with this head and small through put of airated flow I would seem to think it may be a diaphram type. Maybe someone can chime in on this.
At any rate I plan on finishing tomorrow.
Matt,You got mail
[ 04-12-2003: Message edited by: a bear ]</p>
OC_Dmax, Technician,
Thanks for the clarification on the Chassis/Cab lift pump. How is the output of the Aux Tank/Liftpump plumbed to the main tank? Is it through the third nipple on the sender? I’m curious about the purpose of this un-used third connection is on the sending unit.
:confused:
Idle_Chatter
04-13-2003, 07:30
jpblock, that "orphan nipple" on the sender has come up before in transferflow tank installation threads and apparently is an extra plastic casting that is unused. It is solid and has no passage port to or from the sender/tank.
Idle_Chatter
04-13-2003, 09:07
No problem, jbp, I suspect that nipple is drilled-through and used on gassers for the evaporative control canister or some other emissions voodoo.
CntrlCalDmax,
Regarding your question: >>>I have one question on the Stanadyne pump filter. Does anyone know if the filter has an internal bypass for a restricted filter or does the flow decrease when the filter becomes saturated with debris?<<<
I am sure if you call Simon Garner, Director, Sales & Marketing @ (860)525-0821, x 5172 he can answer your question. I've talked to him and found him to be very knowledgeable about his Stanadyne Products.
a64pilot
04-14-2003, 08:16
If anyone is installing lift pumps and is worried about pressurizing the fuel lines or stock lift pump too much there are fuel pressure regulators out there that will allow you to turn the pressure down to as far as 1 psi without affecting flow rate. I've had personal experience with Holley's and it worked very well.
As for the lift pump, I'm not really sure if it is good/bad, necessary/not.
The injection pump has a gear type transfer pump, so pressure will not affect this like a diaphragm. The only thing would be if there was an area that was not designed to be subjected to pressure on the suction side. A leak here would fill the crankcase. Keep in mind that Bosch apparently did not have the forsight to provide an adequate weep hole to seperate the fuel from the oil in the event of such a leak. I believe there was possibly a running change here.
I took a break from my investigation and let A bear go at it for a bit. While our trucks may have different air issues, anything that he finds will help. The biggest problem in all of this is that each time you disconnect something, there is a "rebleeding time, and it's hard to know where to draw the line.
The results of thess tests are at this point inconclusive:
I started by disconnecting the quick connects above the fuel cooler and running to a fuel can. I still had air at the line from the EDU. I observed my suction line, and it appeared to be feeding clear, air free fuel. I had the truck on the hoist, and the can on the floor, and managed to get 7"hg reading with the excessive lift required.
I then moved up to the fitting above the valve cover. I did not want to pull this one as I had it pretty well greased, but I needed to see if I could get it to run clear. The problem I had here, was that I had tiny bubbles drawing up the hose that would accumulate in a high point that I had made to catch them. By this time I was pretty frustrated, and it could well be that these tiny bubbles were coming from a hole in my hose or some other source like a trapped air pocket in the hose as I cannot see inside my fuel can. I'm thinking that I may go back after this one at another time, depending what Abear finds.
I am a bit cncerned to learn that we have heavy use of plastics on the sending unit assy pickup tubes. I have not yet dropped my tank, BUT I did run it down to the Low Fuel light so now is the time...
CntrlCalDmax
04-14-2003, 19:19
a64pilot,
That regulator really sounds good. I would like to lower the pressure to 1-2 psi, just enough to maintain positive pressure. Summit Racing has them on the internet and I will be ordering one tomorrow.
Well this thing keeps nagging me so I dropped the tank and was back at it again. :rolleyes:
I can't use the words I'd like to to describe the fuel pickup but the word cluster comes to mind...
The setup is pretty much like drinking from the toilet bowl with a straw while filling it. :eek: The pickup and return are both located in the same "cup" at the base of the sending unit assy. There is no apparent REAL way for fuel to get into this cup aside from above, and what appears to be a diaphragm type check valve in the floor. The walls of the cup stand a good 3-4" from the floor. I'll be investigating further due to my latest discovery.
I put the tank along side my drivers front wheel and plumbed direct to the engine. The fuel coming from the tank was pure carbonation as air passed through the system. I decided to try moving the return line to dump through the filler as it was obvious that the aerated return fuel was recycling. After a period of running, it seemed to be coming clear, so I went and pumped the primer to try to purge any air trapped in the system. I ended up with a large slug of air in the feed hose as apparently, this cup needs the return fuel to refill it properly :rolleyes:
So, that's how far I got for now. Not sure just what I'll try as my next course of action, but I'm going to try to get it 100% purged and see what happens. It appears that we can run low volumes w/o the return plumbed into this cup, so I may idle it for a bit and see if it comes clean. One thing's for sure, we are recycling our fuel/air...
[ 04-14-2003: Message edited by: kennedy ]</p>
Well after several tests It appears that I have finally stopped the air from entering the fuel. I really don't see it necessary to list all the tests that were done because I think what we are looking for is the end result. Lets just say the testing took about 2 1/2 days of running clear tubing, pressure testing, vacumm testing and pulling the tank 2x. The end result was to change out all 3 push lock fittings on the suction side an replace with fuel hose and clamps. While the tank was pulled I also changed the last 2 near the tank on the return side because of the real low return flow volume and possible draw in of air during the down flow of fuel into the tank.
One thing I did learn is that the push locks are of poor design with only one o ring and a far from good sealing surface, especially the plastic nipple on the tank. IMHO these fittings can't take the line bouncing and vibrations from every day driving without eventually developing a leak. One O-Ring for vac. service is not my idea of a lasting design.
The sending unit is made of plastic with 3 steal rods holding the assembly vertically together. The feed and return lines join together in a small container to help keep tank sloshing from causing air to enter the suction. After removing the bottom cup by compressing the bottom section toward the top and releasing the two catches on the cup I noticed the return line had a U riser to bring the bubbles out the top of the cup. Once the leaks are repaired and the majority of the bubbles are out of the system it works well with clear returns. The key is when the leaks are fixed then the return fuel will clear up. The performance of the assembly exceeded my expectations after viewing it in operation in a clear container.
I can't be sure that all of us with air are
getting it from the same soarce but I would almost bet that the fittings are the majority.
If anyone plans on changing their push lock fittings I have hose sizes for various points that will give a tight leak free fit. Do not use a hose that pushes on easy. Been there, Fought that.
I also plan on changing the pusk lock fittings on the return line @ the fuel cooler and above the valve cover. Don't like it that close to the exhaust manifold.
For those that don't have a Mega filter you can hook up a temporary clear hose between the EDU fitting and the OEM filter as John mentioned. This will validate the integrity of every thing from there to the tank.
By the way I made a round trip of about 100 miles tonight and had maybe a teaspoon of air in the Mega filter. Probably residual that worked out of the dipping lines.
pinehill
04-14-2003, 23:19
Many thanks to both Tommy and JK for taking the time to share all these results with us.
Dittos on many thanks both Tommy and John!!
Tommy, I'm also interested to learn about the hose sizes and types you used (?). I have some
I pushed 3/8 on for my return and it fit snug.
I haven't gotten as far as Tommy, but have been discussing this along the way. My concern is the "recycling" of any air that may enter the system. After seeing the supply pickup, I'm even less inclined to run to the low fuel light...
Bill,
I've learned through the process that a hose that fits tight and had to be worked on was needed to provide a good seal on this vac system. Also I've learned that these small hoses need a good fitting clamp. If a clamp too large is used it will tend to slightly egg shape around the hose and not give a good seal.
These were the sizes I used.
Feed line above drivers valve cover. 3/8"ID
Feed line at tank 7/16"ID
Return line at tank 5/16"ID.
Between EDU and OEM filt for testing 1/2"ID clear vinyl.
Between EDU and OEM filt for permanent use 7/16" ID.
I used Gates regular black fuel hose but I guess any type fuel hose with the ID's listed would be OK. If you don't have a Dremel tool now might be the time to purchase one. It came in real handy to remove the hose above the valve cover where the compression ring is. Just slice the ring with the cut off wheel and pry it open with a small screwdriver.
I've still got some micro bubbles coming from the sending unit, so I'm going to try a smaller clear hose for a tighter fit at the tank to eliminate that possibility. I now have the sender in a pail with depth over the top of the "cup"
A couple of points worth mentioning:
The low fuel light illuminates at approx 1.5" of fuel depth in tank. The "cup" stands approx 5" high. Once below the level of the top of the cup, the return fuel is retained in this cup.
There is a reed type of valve in the floor of the cup through which the fuel used is drawn from the bottom of the tank.
FirstDiesel
04-15-2003, 16:39
Okay John
Since your one of the few that have seen this thing, can you explain what this means???
Why do we need to worry about this cup and why are you less likely to go to the low fuel light now that you have seen it??
With the engine idling, if I pump the primer up a few times, I can basically empty this cup and take in a big slug of air. I did not try to see if it would do so with engine draw only at 3200rpm, but it's gotta be close...
I mentioned to a couple people that I would let them know how the drive panned out. Drove 290 miles to Texas this morning. No air. :D :D :D
Tommy,
Great news! I'll soon be replacing my quick disconnects with new hose and clamps too! :D
Bill,
FYI the hose from tank to the connection behind the fuel cooler is femal on both ends so you can clamp onto the male nipples.
I had to put my tank back in and prepare for some trans work and will revisit this subject later...
Push lock comment - They do make clips that fit on push locks to keep them tight. It may not be the end all cure all but it should help reduce the amount of air. It's raining too much here right now to go under my truck. When I can I'll check the style we have. I might be able to get samples from our vendors for someone to test.
There are clips at the connections above the valve cover.
John,
Thanks for clarifying the tank connection. I was hoping to just remove the OEM hose from the tank and replace with hose and clamps down to the hard line (near the cooler). I thought I would start with this hose and see if it eliminates the air I'm seeing (still no starting or drivability problems).
I was also reading the Helms manual and it has a very detailed procedure for diagnosing air leaks in the fuel system (much like what you and Tommy have done). Likewise they also recommend installing the clear hose between the FICM (EDU) and the filter to detect air. The manual states that if there are NO visible air bubbles, the system is working properly. I wonder how many trucks are running around with air moving through the pump and injectors?
:eek:
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