Engine/Transmission (1998.5 - 2002) So, for fun I take out my fuel tank....

[lberch]

Grasping for a solution to an intermittent stumble at idle. I had changed injectors, lift pump, overflow valve, fuel filter - a gazzillion times and had mechanical fuel gauges duck taped to my windshield for months. I absolutely refuse to go to the dealer.

So I take out my fuel tank, remove the module and find where the fuel pick up is, covered with slimy brown crap. I guess it is actually alge or some other biological growth. I would say about 50% - 75% of the membrane was covered.

For those who don't know, there is a "membrane" not a fine screen covering the top and bottom of the fuel pickup area in the module. I have no idea what it is made of - somebody know??

I carefully took it apart and used everything I thought would clean the crap off - gasoline, mineral spirits, fresh diesel and scrubbing to no avail. What was the only thing that would take it off you ask? Pine Sol, yes, Pine Sol.

Long story short, that was a month ago. My lift pump out put pressure (pre-filter) greatly stabilized (stopped bouncing so much) and not a hint of stumble at idle. Hope this info helps somebody else.

 

[Texas Diesel]

Great Job!!



Guess I need to start regular, periodic, biocide treatments.

 

[Cliffman]

Way to go lberch. I grew up in S. Fla. If it's ever lived, it's lived in Fla. Lots of critters there

 

[Jim Fulmer]

Could it be microbiological growth, very bad in aircraft. Fuel samples are taken before the first flight of the day because of it and it comes from water in the system.



Jim

 

[MWilleford]

"Miss" at idle, intermittent

lberch,



I first though I had a lift pump problem, but as you did, I drove around with a fuel pressure gauge taped to the outside of my hood for a week, until I figured/assumed it was a bad tank of fuel (first time in over 30,000+ miles i have ever had a "miss" at idle). I worried and after my next fill up, it went away.

But it is back again after another 2-3 tanks.

I've used standard fuel supplement, but that has not cleared it up.



Please let me know if you had similar sympoms:

-Miss/stumble at idle, and intermittent only once warmed up (not when cold)

-"Acceptable" fuel pressures

-No performance or mileage changes.

-No visible signs of fuel filter restriction.



I'm going to try and find some cleaner that might clean the tank without having to remove it. I've heard of systems becoming contaminated, but only when they sit for an extended period of time. I'll advise if I find any conditioner/cleaner.



This stumble/miss can drive a man in sane

 

[ralphr]

last summer I noticed similar growth when I changed fuel filter, ( this is not a plug) but, I used amsoil diesel fuel conditioner, I think the directions say 2 oz per 100 gals or something, I just poured the hole bottle in the tank and drove it empty, re-filled and put in half bottle, changed filter and repeated with "by directions" since then be ok.



been around a lot of boats and all use bio something or over on a regular basis. also heard keep tank full, half full allows to much water into fuel which allows bacteria to grow!



where in south florida do you live? I lived in kendal area for 27 years before moving.

 

[Big_Daddy_T]

wow ralph i though i was the only one who had that kind of crap happen. Good work. I had a suby that missed when there was someone sitting shotgun. this continued for 30k very intermittently. i ripped the car apart looking for the ecm . the #4 injector wire was shorting out. unfriggin believable. my mechanic thought i was insane. it only missed when a heavy set person was sitting shotgon and not always just sometimes. the ecm was located under the feet of the passenger on the floor towards the firewall where a big persons feet rest.





P. S. im going out to get some biocide today.

 

[lberch]

Mwilleford- A little more background on my troubleshooting:



Last August (@28,000 miles) I had 1 miss at idle (engine cold) @ 80F here in south Florida. From there, the miss got worse/better/worse/better and would change from missing when the engine was cold, to when it was warm, to both and then go away completely for awhile. I never had a change in performance or mileage and never saw but a little black on my fuel filters. Thats what was so frustrating the intermittent part.

I was convinced for a while that it was a sensor because if the temp dropped below 70F the miss would get worse. No codes ever set other than the ones I caused, all sensors checked out.

Got two mechanical fuel guages. The first thing I noticed was that @ idle my pressure was a little low about 11-12 psi pre, and 9-10 post filter. At WOT it would drop to 2-3 psi or lower. So great! I think I got this thing wooped! Change lift pump, got 15psi @ idle no filter restriction, and can't get it to go below 8 psi @ WOT. Still I have an intermittent miss @ idle.

I do notice that when the miss was at its worse it pulsed both guages to spike higher pressures when it missed. If I put in a huge amount of injector cleaner (1 gal plus) I would never have a miss. So great! I think I got this thing wooped! Change injectors runs fine, still have an intermittent miss @ idle.

Now I am getting depressed at thought of possibly having to accept defeat and go to the dealer.

I would stare at the pressure guages for hours on end, my wife doesn't "think" I am nuts, she "knows" I am nuts.

I notice one other subtle detail. When I would change the fuel filter and prime 3 times and start the engine, both pressures would be almost rock steady @ 15psi pre and 14psi post for several minutes and then the post would start to fluctuate between 12-14 psi and then the pre would start to bounce 14 -15 psi. But it would be steady for several minutes after the filter change. By the way before this point I had already taken out my overflow valve and tested it and it was OK. But I said, with a very small psi spread that this valve has to meet i'll just change it. Still had an intermittent miss @ idle.

Something troubled me about the pessures after the filter change. So I took out the fuel tank and the rest is history.

The problem I see in the stock set up is that If you have growth or contamination (me) and you kill it, it is still in your tank and will accumulate on this "membrane" and cause a restriction. So, some time in the future I will remove the "membrane" in the tank and install an inline pusher pump with a "Racor" replaceable filter that is outside the tank.



LB

 

[Steve Campbell]

Same situation....different year.......

Man-O-man did I have fun this afternoon. I had been looking through old threads like this one to confirm my suspicions about the fuel pick-up membrane. I decided that I had put it off long enough and started in on the job after church. 5 plus hours later, fuel shower, tool invention, you name it... . it all seemed to happened to me today.



I put the truck in the shop with all of that snow (I shoveled and swept off as much as I could) dripping down my neck. The main fuel filling hose was really muddy. Then I had trouble figuring out how to undo the electrical connection (finally got a mirror so I could see it). Next problem was a "wrench" big enough to loosen the retaining nut (I wound up using a short lenght of rope, wrapping it around the nut, twisting the ends and then turning the nut with the "Handle" I had just invented.



Talk about a plugged membrane... . when I went to lift the module out, none of the fuel had drained back down... whalla... instant diesel cologne.



Anyway... the rest was easy... I used a toothbrush and some gasoline to rid the mesh of the accumulated "stuff".



Putting it back together was the easy part..... which is the exact opposite of my usual endeavors.



Fuel pressure restoredOo.

 

[Ncostello]

When I had my module out... I found it much easier to take out 6 bed bolts, disconnect the tail lights, and remove the filler neck screws holding it to the bed. Me and two friends lifted the bed off without a problem. Not really that much weight there at all.



For those wanting to look inside the module I have some pics. You can see the mesh (silk like) material.



99 fuel module



I was suprised to see the inside of the tank was sparkling clean. All I saw inside were a few very small sand like particles sitting on the bottom. I figured they were not hurting anything.



PS: I exacto-knifed the screen mesh out of there and installed a spin on 30 mic filter head in front of the tank. Never have to worry about the inside of the tank again. Any crud will show up in the pre filter.

 

[Steve Campbell]

Ncostello......

I considered the bed removal/tilt thing, but just being me/myself/and I ..... I opted for the "other" thing. When the weather turns a bit better (and I can round up a buddy) I think I will model my fuel delivery system to something like you did in the other fine threads that you have shared. i already printed out all of your pictures and instructions to have on hand for the big day.

 

[Sticks]

You don't really have to pull the bed do you? Can't you just jack it up a foot, just enough to get clearance to lift it out?

 

[Ncostello]

Just jacking it up will work I'm sure. Watch the bed quarter panels on the bumper. They might hit if you go too high.



True... I did have help to get it off. But I had a lot of work to do around the tank. And I wanted to clean the frame well and get some good angles for photos.



Plus... I dont think I could have removed my module nut/retainer without standing above it for leverage. It was tough to get it to turn for the first time. I finally figured out to use a blunt punch and a slight tap of a hammer. No wonder they service manual shows a special spanner wrench.

 

[Dane]

I never have understood the logic of a strainer in the tank when it's so darn hard to get to!?



I had a similar problem on my 66 Chrysler 300. Turns out rust had clogged the strainer in the tank...



I like the idea of ditching the strainer and having a filter just outside the tank. That's what I did on the Chrysler. I use a clear filter so I can see when it's getting clogged.



What about an access door cut into the bed of the truck to get to the top of the fuel tank?

 

[Forrest Nearing]

Originally posted by Dane



What about an access door cut into the bed of the truck to get to the top of the fuel tank?

oh man, my bed's already so hammered up, I may go and build an access door in anticipation of future maintanence!!! good idea!



Forrest

 

[Ncostello]

I don't want to sound like I'm nagging anyone... but removing or at least unbolting and lifting up the front of the bed is easy. By the time you fabbed a access door you could remove and replace the bed. Plus you might want to lift it anyway to make sure you dont hit the tank sending unit while cutting a hole. At least be super careful.



I'd rather remove the bed than rotate my tires in the garage. It is definately easier and faster. Plus if you do it and rip out the screen, you'll never have to do it again.



Be aware that the mesh fabric does more than just filter incoming fuel (at least to the best of my analysis of the total system thats what I believe). The module actually is a reservoir of sorts for fuel. The return line empties into the module. The module is a closed cell up to about 3/4 tank. Thus any fuel that is in the module tends to hang around a little while. What I mean is that for it to escape it has to pass through two layers of screen mesh (which looks like silk fabric), out the bottom of the module and into the fuel tank. You can see through the mesh but not actually see mesh fibers. Its is not like a screen on a back door. Thus it takes some amount of time (t) to go through the mesh "trap". That time may be important to Dodge engineers.



So at 1/8 tank... fuel will slosh away from the bottom of the pickup point. The fuel at 1/8 tank level in the module begins to pass out of the module through the mesh "chamber" surrounding the pickup tube. As this chamber is continually flooded with module reservoir fuel... the pickup is constantly submerged in fuel until sloshing fuel comes back to the bottom of the module.



I had great concerns about "ruining" my module when I cut the screen out. I was worried about sucking air at times of low fuel levels, sloshing fuel, or driving up hills thus causing fuel to go away from the pickup point.



My determination is that sloshing fuel in a 1/4 tank will never allow the pickup tube to be without fuel (99% certainty based on scaled drawings and the tank geometry). Plus it would take an extreem grade to cause 1/4 tank to pool away from the pickup point. Something like 45 degrees or more on hills perhaps. I had a couple big buddies of mine help me rock the truck with 1/4 tank. I watched inside the tank (module removed) as the 1/4 tank sloshed back and forth. There was never anything close to fuel running completely away from the bottom of the module. And slosh it does!! That fuel was really rolling in there and splashing violently to and fro.



I've ran 1/4 tank and sloshed it around and driven up the steepest hill I could find without ever loosing prime (pressure) at all. I've never had a problem at all. I've also never been caught below 1/4 tank either. I wouldn't advise that anyway.



I believe its OK to remove the screen... just be aware it might do more than just screen fuel for contaminates. I posted this info somewhere else. I hope its not real confusing as I need some sleep.



PS: I tried asking Dodge about the design of the module. That didn't get far. I also contacted the people who actually make the module. They didn't have a clue about its design really... or at least played dumb (as if the person who engineered it no longer exists and neither do the design parameters). A new one is $440 so choose wisely and be careful. And although the screen is removeable it is not available as a part #. The fuel level unit however is.

 

[Forrest Nearing]

my bed is already hammered up and has multiple holes in it... I figure I'll be in there replacing the sending unit or some fuel lines etc. at some point or another... I'm all about easy access. I can promise you that when/if the bed gets lifted, it's getting an access door made!



Forrest

 

[Steve Campbell]

Ncostello said.....

..... "And slosh it does!! That fuel was really rolling in there and splashing violently to and fro. "



I wonder why DC does not design in some baffles to slow that ... ... "splashing violently to and fro"..... to a more moderate level. As I understand it, the FASS system is all about taking out that entrained air that happens when the fuelgoes... . "splashing violently to and fro"





..... "So at 1/8 tank... fuel will slosh away from the bottom of the pickup point. " (previous courtesy of Ncostello)



I have said in the past in threads regarding the fuel level in the tank vs fuel level on the guage not corresponding (something like 4-7 gallons remaining~~~would that be around 1/8th of a tank of fuel left in most tanks when the guage reads empty)..... I think Dodge designed it this way to avoid what Ncostello just pointed out so well.

 

[Grey Wolf]

In the past 30 plus years of driving Diesels I,ve had that happen a couple of times too I,ve found this product to be the best for prevention... ... ... ... ... Biobor® JF.



Around here it can be purchased in the harbor areas, but here is another place to get it.



http://www.hammondscos.com/fuel/biobor_jf.html

 

[Dane]

So, If you get a big gob of bacteria/fungus from the tank at the filling station will the products for keeping the gook from growing help?



I ask because some of the filling stations I use have filters in line with the filling hose and some do not.