Foaming fuel - PeachParts Mercedes-Benz Forum

Diesel-Lover · #1 01-07-2003, 12:05 AM

Has any one here had trouble with diesel fuel foaming and thereby causing the filler (gas station) nozzel to shut off before the tank is full (i.e. making one "spoon feed" the tank).

Is there a remedy for this problem. I have experienced this on my MB, Ford E350, and also on GM Diesel motor home.

On the MB if I position the fuel statin nozzel just so, it will fill properly, but it is a hit or miss process, generally ending in not being able to use the automatic shutoff process.

During my vacation this past two weeks, I literally had to spoon feed the tank, and 50 Gal takes a long time.

I notice the filler has some kind of slotted sleeve with a nozzle trap door(spring loaded), the foam comes up through the slots, perhaps I should take the slotted sleeve thing totally off, or will that make the problem worse?

Removing the contraption will also allow me to use the truck fuel pumps.

I had the least problem during the trip in KY ! Most in TN and TX but have experienced this issue off and on in many places.

Thank you for any and all constructive input.

rwthomas1 · #2 01-07-2003, 12:12 AM

I have been told that diesel fuel expands quite a bit when heated so filling the tank to the very top is not recommended. The theory goes that the cold fuel from underground tanks will expand when heated by the engine (some fuel returns to the tank when running) and on a hot day may overflow the tank? I don't really buy it but then again I don't fill it all the way up either. My 84 MB will fill all the way to the top without any problem foaming or otherwise though. RT

The Warden · #3 01-07-2003, 12:18 AM

As far as I can tell, my 300D doesn't have this problem, but my F-250 sure as heck does!! I just refueled the truck today, and was at the pump for nearly an hour.

The problem is with the vent system. I had an E-350 van before I got the 300D, and I also used to have a diesel IH Scout. BOth of these vehicles had the same problem as the truck. Basically, there's a vent for the tank that gets clogged up with foam before the tank gets all the way full. There's a company out there named Transfer Flow (www.transferflow.com I believe) that makes updated fuel filler necks that are supposed to cure this, but for Ford picups, they only have them for '87 and later years. I don't remember what the availability's like for an E-series.

I think you can remove the slotted piece and not have a problem, but I'm not sure there.

Also, FWIW, except on the Benz, I always fill my tanks to the brim, and have never had a problem with a tank overflowing, except once when the fuel selector valve was messing up on my truck and was sucking fuel from the forward tank and returning to the just-filled rear tank...

Hope that helps some...good luck!

tryan · #4 01-07-2003, 08:50 AM

i have the f250 foaming problems also.at citgo , 10 minutes for the first 24-25 gallons and another 10 minutes to get the last 8 gallons. yes that ford 29.5 gallon tank holds 33.5 gallons. i fill up the day after they fill their tank.

i have filled up at pilot truck stops a couple times. no foam/good fuel, but you do have to baby the fuel with the bigger nozzle.

Diesel-Lover · #5 01-07-2003, 03:39 PM

It seems as though I fill my P30 based Diesel motor home more often than any of the other vehicles and frequently in short periods therefore it is the most painful not to mention the large capacity tank 75Gs. It has the slotted do hicky as does the E350 Diesel. This spring the slotted dohickys are coming out one way or another from both the GM P30 MH and the F E350.

The MB filler tank neck will have to be looked at a bit before I can do any thing with it. I hate to mess with it as I am afraid of screwing something up, including cosmetics where as with the others cosmetics are not an issue.

Looked at the link with the replacement filler neck parts, kinda pricey but if the slotectomy does not work I will have to bite the bullet for those. Gosh 70-90 bucks for a bit of hose and clamps is kinda steep! but if the market bears it hey more power to em! They do have a nice selection of tanks and pumps, will be a nice parts source later on in a few years when I am ready to tackle the fry oil driven conversion process. I would like to get the MB to 250K before I would do that, its around 165K now.

Thanks all for the info. good to know its not just my machines!, I was beginning to think that some one had poured some bubble soap in my tanks or something. Wonder why GM and Ford have not put in a fix to the filler neck design. The MB filler neck is picky but not too bad, though there have been days when I just left after getting 10 Gals into the MB for lack of patience.

Weeel happy motoring and a fantastic new year to all.

Rick Miley · #6 01-07-2003, 05:34 PM

I have read other places that foaming means that the fuel is fresh. Somebody who knows what they're talking about (not me!), please comment on that.

As for the truck nozzles not fitting because of the restrictor, that has not been a problem for me on either the Jetta or the MB. I pull right up to the truck island and shove that baby in as far as it will go. The restrictor plate stops it, but it will still stay in and fuel up just fine. Of course, the fuel is flowing faster so the foaming is even worse.

The Warden · #7 01-07-2003, 06:04 PM

Diesel-lover, I'm just curious. What engine does the GM motorhome have? Also, what year's the E-series? Have you evern been over to www.thedieselstop.com ?

On the Benz, I just put the fuel nozzle on the lowest auto setting they've got...I think I've put up to 18 gallons in the car. There's some form of vent under the car that I found; I'm not sure what it's exact purpose is, but it may be like the vents that go into the filler nozzles on the Fords.

Diesel-Lover · #8 01-07-2003, 09:11 PM

How do Warden,

The E350 is a pre turbo edition last year before the turbo, extended type people mover which belonged to an airline b4 I did a hack job on it and tried to convert it into a ClassB cruiser. It is almost sold now as a fellow is making arrangements for payment, may have to strip out the dinette as he wants to make it into a work van, it has quad seating up front with a micro and a fridge, then the rest is open.

The GM is a 6.5 TurboDiesel, what has me stumped is that the engine heater plug is round like in england! It is in a Winniebago (30B is the model number if I recall correctly). This one is circa 1999 bought new up in the portland area over the internet! now it has about 23K on it. It is a puller, once warmed up it quiets down except when going up big hills. It has been doing a respectable job for me, when we would go out of phx up the hill for the cool weather of flag, I could beat most gassers up hill without probs, even keep up with some of the smaller engined pushers at times, but most of those bigdogs would blow the doors off mine.

Will have to see the diesel stop site next. Been hankering for a chip but wonder if the switch will get captured in the electronics somewhere, as do not want to muck up my 100km drivetrain though after another year it will be history anyway unless I get an extended one.

Now I kinda wish I had sprung for a pusher, but then again the new price for those is way too high.

rwthomas1 · #9 01-07-2003, 09:20 PM

Hey Diesel-Lover,
If you don't already know you should check out www.thedieselpage.com Its an all-GM diesel site that is worth its weight in gold if you own a 6.5. They ain't known for reliability and the forum there is top-notch if you have problems or questions. Also some vendors for speed/power/reliability parts as well. Its a paid membership site, like 15$ a year which will pay off with your first question answered. Check it out. RT

PaulH · #10 01-07-2003, 10:19 PM

Rick - You may be on to something. The only place that I have "foaming" problems is at a station that is very busy all day long and has fresh fuel. And my SDL runs great on this fuel! I just put the pump handle on "slow" and cool my heels. Some of the truckers give me dirty looks for taking a little extra time.

BobK · #11 01-08-2003, 07:21 AM

I think the foaming is also due to the seasonal blend the fuel company uses. I seem to get more foam in winter when they have put the conditioner in the fuel. I buy most diesel at a local Flying-J truck stop at the auto island (12 pumps, only 4 with diesel-waaahh). Fuel is excellent quality and since they are usually the cheapest around, the fuel is always fresh. No idea what the cetane is for the fuel.

tryan · #12 01-08-2003, 08:41 AM

i get the foam in summer and winter. 20 minutes to fill up.

i fill it to the top of the fill nozzle EVERY time. the truck runs like crap all winter long. it's a powerstroke thing. they all run bad after 99.5 production with the california split shot injectors. 7.3 liters of marbles.

#13 01-08-2003, 08:23 PM

its time for you guys to get some biodiesel.
Diesel fuel expands LESS than gasoline.

lrg · #14 01-10-2003, 01:20 AM

My understanding is that you do get some very slight temperature expansion with both diesel and gasoline. However, common sense tells me that it can't be much since if it was every big service station out there would be preheating the fuel so they would get more $$ per gallon (which is a volume measure).

psfred · #15 01-10-2003, 09:06 PM

Foaming is normal with diesel fuel -- gasoline foams just as much, but is much less persistant that the diesel foam.

Check the vent system for obstructed lines -- MB usually has a dual line system, and if one is plugged, neither will drain. Some models (W123 and later, I think) have the vent line terminate under the vehicle with a funky perforated diaghram rubber thingy -- perfect size for a mud dauber to build a nest in. Some spiders like them, too --- needless to say, tank vent problems!

Make sure the nozzle isn't completely filling the opening in the tank while filling, too -- most of the air in the tank has to come out the filler.

Use a slower fill rate, you get less foam and it will fall faster, and the tank will vent better, too.

Peter