Foamy Diesel - Page 2 - PeachParts Mercedes-Benz Forum

Since66 · #16 09-17-2009, 05:31 PM

It's the nature of diesel to foam when agitated. Just try not to let the nozzle/trigger pump at full force when you're almost to the top of the tank. The foam subsides quickly. It is of no consequence, really

tankowner · #17 09-17-2009, 05:36 PM

Quote:

Originally Posted by b2948kevin

So, after reading the results above, I was a little frustrated (with hearing that I had to put up with it) and decided to go away quietly

. Now nearly a year later, I've been doing some pretty hefty work on this car and want to re-open this.

I want to reaffirm that after owning this for nearly 2 years, all diesel pumps cause the same issue with foaming, and that after running multiple treatments of algae remover, I still have the same issue. I cannot even get half way to the first notch on the pump lever catch before the diesel foam comes out of the filler and onto my shoes. If I barely run the pump, it will continue to fill (at the approximate rate of 1 gallon per minute), but I can see foam in the filler tube. This happens exactly the same when I have 15 gallons in the tank, or 1.

This is causing me to spend 20 minutes at the gas station holding the filler just to the point of barely running. I usually give up after 5 gallons or so. I hope you can understand my frustration.

Has anyone had this severe of an issue?

Does anyone know of some sort of tank vent line? A mechanic told me that there was one on the tank, but I've been unable to locate it thus far.

I'm afraid that I don't really have a good response other than to say that I was surprised at the number of previous responses that thought this was normal. Diesel foams, yes, I agree - but spending 20 minutes to fill the tank seems very excessive to me. I don't know how tank shape, tank volume and fuel vent placement might ultimately affect this - such that some models would a higher foaming factor (technical term) - but I can tell you that I have never had a problem with foaming - even if I use the giant truck nozzles (that don't even fit in the filler tube) at full blast.

If you are saying that you can't even fill at full blast for 5 seconds on an empty tank, then there has to be something going on here. Maybe I am wrong - it surely wouldn't be the first time, but this sounds very strange to me. The fact that some people experince this (although this sounds like an extreme version) and some do not, tells me that there are some variables at play.

Yes, your tank has a vent, not sure where it is located on your model though. I would think that it might have something to do with this, so figure out where it is and make sure it isn't clogged.

bustedbenz · #18 09-17-2009, 06:42 PM

Is the wagon tank shaped significantly differently than the sedan tank with which most people are saying "it's not an issue"? I'm envisioning a differently shaped tank causing an increase in natural foaming simply by nature of how it's built.

I've never heard of any type of algae problem or any such "cure-able" occurrence for this problem. Maybe pull your tank out of the car and inspect it, shine a flashlight into it, look for trouble, deformations, etc? That's the only thing coming to my mind. There's not a "super-foaming bug" you can clean out of the tank, that I've ever heard of.

b2948kevin · #19 09-19-2009, 04:50 PM

Quote:

Originally Posted by 79Mercy

I have never had that trouble with my 300D.

I think its a problem with the tank vent, just as your mechanic said. After driving your car for a while remove the fuel cap, do you hear a sucing sound when you remove the cap? If so its a clogged vent line.

Let me check that out, Merc. I appreciate some good troubleshooting tips instead of just saying this is normal. I'll need to start looking for that pesky tank vent. Good to have confirmation that there is one. I don't know much about this part of my Benz. I'll try your trick for listening for suction.

Quote:

Originally Posted by tankowner

I'm afraid that I don't really have a good response other than to say that I was surprised at the number of previous responses that thought this was normal. Diesel foams, yes, I agree - but spending 20 minutes to fill the tank seems very excessive to me.

If you are saying that you can't even fill at full blast for 5 seconds on an empty tank, then there has to be something going on here.

Totally agree! I am a very reasonable person, have owned 2 of these before, have driven tons of different diesels from pickups to peterbuilts, filled thousands of gallons of diesel and have never had such a severe case of foaming. Believe me when I say that it's not normal for diesel to foam this much. Also, after letting off of the filler after foaming up, it does not subside after a few seconds. The foam remains in the filler tube.

Quote:

Originally Posted by bustedbenz

Is the wagon tank shaped significantly differently than the sedan tank with which most people are saying "it's not an issue"? I'm envisioning a differently shaped tank causing an increase in natural foaming simply by nature of how it's built.

The different tank may be a factor in this too. I cleaned the fuel sender about a year ago and had the opportunity to look in the tank with a flashlight. I saw some particles in there, but it looked fairly clean. I also changed the tank filter at that time. The old one didn't look as bad as I expected it to.

So, here are my next steps:

Research where the tank vent is for the wagon and inspect it.

Try 79Mercy's method to listen for a suction sound.

If all else fails, pull tank and have steam cleaned by radiator shop.

I'll keep you posted on how I progress. Meanwhile, if another wagon owner knows where the tank vent is located and routed, I would be greatful.

jnc19610 · #20 09-19-2009, 07:48 PM

I thought diesel foamed a lot when I first got my car.
I usually start out fast, then slow down as it fills up.
this has minimized the foaming concern.
When I have time, I top off, otherwise, it's about a 3 gallons short of a fill.
I think this is mainly due to the venting system.

For your foaming problem... I have an idea.... Go buy a funnel... with a screen in it. good sized one, or put an extension hose on it. Find one like you might use to fill a race car (like for a sprint or modified car). they are big, they have a screen. Try to figure out what is foaming... does the fuel foam in the funnel.. or does it foam after it hits your tank.

Perhaps the screen will help deairate the fuel before it hits the tank.

just an idea.....

jkubica · #21 09-20-2009, 05:51 PM

Quote:

Originally Posted by b2948kevin

So, after reading the results above, I was a little frustrated (with hearing that I had to put up with it) and decided to go away quietly

. Now nearly a year later, I've been doing some pretty hefty work on this car and want to re-open this.

I want to reaffirm that after owning this for nearly 2 years, all diesel pumps cause the same issue with foaming, and that after running multiple treatments of algae remover, I still have the same issue. I cannot even get half way to the first notch on the pump lever catch before the diesel foam comes out of the filler and onto my shoes. If I barely run the pump, it will continue to fill (at the approximate rate of 1 gallon per minute), but I can see foam in the filler tube. This happens exactly the same when I have 15 gallons in the tank, or 1.

This is causing me to spend 20 minutes at the gas station holding the filler just to the point of barely running. I usually give up after 5 gallons or so. I hope you can understand my frustration.

Has anyone had this severe of an issue?

Does anyone know of some sort of tank vent line? A mechanic told me that there was one on the tank, but I've been unable to locate it thus far.

Hi
Is the flap inside your filler tube opening fully? It's operated by vacuum. On the wagon you can open up the first aid/jack compartment - right side rear and tie open the flap with a wire on the vacuum switch. Then try filling it again.

Good Luck,
Joseph

tbomachines · #22 09-20-2009, 05:55 PM

Quote:

Originally Posted by jkubica

Hi
Is the flap inside your filler tube opening fully? It's operated by vacuum. On the wagon you can open up the first aid/jack compartment - right side rear and tie open the flap with a wire on the vacuum switch. Then try filling it again.

Good Luck,
Joseph

Are you talking about the fuel filler door? You wouldn't be able to fill up the car without getting to the fuel cap...

jkubica · #23 09-20-2009, 06:27 PM

Quote:

Originally Posted by tbomachines

Are you talking about the fuel filler door? You wouldn't be able to fill up the car without getting to the fuel cap...

Hi
The flap is located about one foot down the filler tube. May be designed to stop crooks from stealing fuel with a hose - at least my 1985 300td has this setup - not sure about other years
Joseph

hobbitss · #24 09-20-2009, 06:50 PM

Quote:

Originally Posted by jkubica

Hi
The flap is located about one foot down the filler tube. May be designed to stop crooks from stealing fuel with a hose - at least my 1985 300td has this setup - not sure about other years
Joseph

Excessive foam and a very slow fill sounds like a fill tube restriction...

tbomachines · #25 09-20-2009, 08:41 PM

Quote:

Originally Posted by jkubica

Hi
The flap is located about one foot down the filler tube. May be designed to stop crooks from stealing fuel with a hose - at least my 1985 300td has this setup - not sure about other years
Joseph

Hm interesting, I never knew that was a feature. My SD doesn't have that to my knowledge, the only thing pulling the lever does is allow the filler door to open. The filler "neck" is only a few inches until it opens up into the tank. I can shine a flashlight down and see the entire thing.

jkubica · #26 09-20-2009, 08:48 PM

Quote:

Originally Posted by hobbitss

Excessive foam and a very slow fill sounds like a fill tube restriction...

Hi
That's just the point. When the flap is closed, the fill tube is restricted.
Joseph

jkubica · #27 09-20-2009, 09:03 PM

Quote:

Originally Posted by tbomachines

Hm interesting, I never knew that was a feature. My SD doesn't have that to my knowledge, the only thing pulling the lever does is allow the filler door to open. The filler "neck" is only a few inches until it opens up into the tank. I can shine a flashlight down and see the entire thing.

Hi
The 300td wagon has a flat tank underneath. It also has a separate expansion tank in the first aid/jack compartment at the right rear. When i shine a flashlight in my filler tube I can just see part of the flap where the filler tube begins to bend toward the tank. The flap is opened by vacuum and if not working correctly makes the tank very hard to fill - just as the OP complained. Must be a differant system entirely from most other models.
Joseph

tankowner · #28 09-20-2009, 09:21 PM

Quote:

Originally Posted by jkubica

Hi
Is the flap inside your filler tube opening fully? It's operated by vacuum. On the wagon you can open up the first aid/jack compartment - right side rear and tie open the flap with a wire on the vacuum switch. Then try filling it again.

Good Luck,
Joseph

That's very interesting, I hadn't heard of that feature - a vacuum operated flap in the filler tube, huh? As you suggest, I guess the feature would be to deter fuel thiefs, but that still seems strange if the fuel door locks via vacuum with all the other doors and the trunk. It really sounds like this must be the problem - it would certainly seem to explain the OP's inability to fill for a even a few seconds without overflowing with foam and the incredibly long time it takes to fill the tank. The length of time stated for the foam to subside is then likely due to slow draining of the fuel past this flap. It will be interesting to see if this is indeed the problem - almost seems like it has to be.

jkubica · #29 09-20-2009, 10:11 PM

Quote:

Originally Posted by tankowner

That's very interesting, I hadn't heard of that feature - a vacuum operated flap in the filler tube, huh? As you suggest, I guess the feature would be to deter fuel thiefs, but that still seems strange if the fuel door locks via vacuum with all the other doors and the trunk. It really sounds like this must be the problem - it would certainly seem to explain the OP's inability to fill for a even a few seconds without overflowing with foam and the incredibly long time it takes to fill the tank. The length of time stated for the foam to subside is then likely due to slow draining of the fuel past this flap. It will be interesting to see if this is indeed the problem - almost seems like it has to be.

Hi
The fuel door doesn't lock on the 1985 300td. It opens by just pressing on the right-hand side of the door and it pivots open. It is the flap down inside the filler tube that opens/closes via the vacuum system.
Joseph

tankowner · #30 09-20-2009, 11:13 PM

Quote:

Originally Posted by jkubica

Hi
The fuel door doesn't lock on the 1985 300td. It opens by just pressing on the right-hand side of the door and it pivots open. It is the flap down inside the filler tube that opens/closes via the vacuum system.
Joseph

Well, there you have it - I didn't know that. I guess you learn something new everyday. Thanks.