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-   -   Fuel overflowing tank! Will not drain (http://www.peachparts.com/shopforum/diesel-discussion/220369-fuel-overflowing-tank-will-not-drain.html)

tsw27 04-23-2008 09:43 PM

Fuel overflowing tank! Will not drain
 
Hi all. It has been sometime since I have posted. Been lucky I guess. I own a 1984 300D. She runs great except...when I got home from work I noticed a big puddle beneath the benz. It is diesel fuel which had got into the trunk.

So here is the problem:
Fuel is backing up out of the tank, it is over flowing. The car still runs, so fuel is getting to the engine, but why is the tank backing up past the filler neck through the fuel cap? Fuel gage reads 3/4 full so there is not too much fuel in the system. In fact, I filled up (a full tank) 2 days ago and have put nearly 100 miles on the car so I know there is no way the tank is too full. Unless of course the miracle finally happened and my car is now running on air...ha ha.:P

If anyone can help with this I would really appreciate it. We are a one car family so this would really put us in a bind if I cannot solve this.

Thanks in advance

Thomas

babymog 04-23-2008 10:01 PM

I'm not familiar with the 123, but do you possibly have a leaking fuel return hose in the trunk?

tsw27 04-23-2008 10:16 PM

No, no leaking return hose. The fuel in the trunk is not the issue it was just the sign that something was amiss. I just cleaned out the little bell shaped vent thing that runs back to the fuel tank. It was a bit clogged. I ran her around the block a few times, but still the fuel remains at the top of the filler neck. It still will not retreat. WTH?

I was wrong though about the miles I have traveled since I filled up. I just checked the trip at it reads 40 miles. But still, at about 22 mpg a too full fuel tank should not be the issue. Besides, if that were the problem I would have noticed this overflow 2 days ago.

toomany MBZ 04-24-2008 05:50 PM

Perhaps you need a new seal on the fuel cap.

bgkast 04-24-2008 06:59 PM

Your car is creating fuel. Put a tank in the trunk to collect it and sell it to me. :D

Seriously, maybe you have a hole in the tank. That is the only way I can think of that fuel would end up in the trunk.

barry123400 04-25-2008 02:36 AM

There is a possibility your vent line is blocked and the tank has collapsed a little with the created vacuum. I can not figure any other way the fuel could still be at the top of the neck. Forty miles driving should have dropped the level about a gallon and a half.

vstech 04-25-2008 09:29 AM

check the condition of both the seal on your fuel cap, and the seal that surrounds the fill neck mine were very cracked, as you drive, the fuel sloshes around and splashes against the cap, then the fuel dribbles down the neck and leaks into the trunk. I bet. even if you have the amazing fuel producing car, a new seal (about $2) will hold in in.

t walgamuth 04-25-2008 10:27 AM

YOu may have just left the cap loose or crooked. Also there is a drain from the filler area that runs through a tube through the trunk on some models. check the drain from the little filler door area.

The tank must have been filled from a cold tank and the heat is expanding the fuel now. Drive it and it will have to go down.

Tom W

tsw27 04-30-2008 08:27 PM

Thanks all for responding. The seals are good, but I will replace them anyway.

The problem went away for a while. So I figured that is was simply diesel fuel expanding with heat. But today another huge puddle of fuel underneath the car. I am at less than a quarter tank. What the heck is going on?

In any case, Friday I am taking the car in for a valve adjustment. I'll ask my mechanic to see if he can locate a hole in the tank or whatever. I hope it is not too serious. This is car is a 97 percenter, and I want it to stay that way. Thanks all for responding. If I figure it out I'll post the solution.

Thomas

SWjames 08-01-2013 07:36 PM

What did the answer to this turn out to be? I've got the exact same problem which just started on my 240D this last fill up.

Diesel911 08-01-2013 10:41 PM

Quote:

Originally Posted by tsw27 (Post 1840445)
Thanks all for responding. The seals are good, but I will replace them anyway.

The problem went away for a while. So I figured that is was simply diesel fuel expanding with heat. But today another huge puddle of fuel underneath the car. I am at less than a quarter tank. What the heck is going on?

In any case, Friday I am taking the car in for a valve adjustment. I'll ask my mechanic to see if he can locate a hole in the tank or whatever. I hope it is not too serious. This is car is a 97 percenter, and I want it to stay that way. Thanks all for responding. If I figure it out I'll post the solution.

Thomas

It could be the Tank Vent is plugged up higher than the Bell

Diesel911 08-01-2013 10:42 PM

Quote:

Originally Posted by SWjames (Post 3185627)
What did the answer to this turn out to be? I've got the exact same problem which just started on my 240D this last fill up.

The OP did not get the best of responses. So He might not have come back.
His last post was Sep 2008.

Diesel911 08-01-2013 11:00 PM

1 Attachment(s)
Is your problem exactly the same as the Original Posters?

I find it hard to believe that He had 1/4 Tank of Fuel and that Fuel was getting pushed out of the Fuel Fill neck unless his Fuel Tank was collapsed.

You might want to remove the Sheet Metal Barrier in the Trunk and get a good look at the Fuel Tank.

In the pic is the Vent Line in Red and the Vent Line Hose circled.
If the Circled Hose collapsed that would render the Fuel Tank Vent useless.

vstech 08-01-2013 11:22 PM

what part of the country are you in?
is rust a problem with your car? have you looked at your filler cap gasket?
look in the trunk, there is a rubber hose that connects to your filler neck that can leak fuel into the trunk, and it'll leak onto the pavement on the passenger's side back tire area.

SWjames 08-02-2013 03:29 AM

The problem started today (well, when I got home today I noticed that there was a major diesel spill where I had been parked, so I guess it started after my last fill, which was Monday.) I noticed some diesel pooled in the pass fender well in the trunk (there are no plugs in the fender wells or carpet in the trunk, I assume they were removed by the previous owner because the trunk seal and or the rear window seal leak so I am still guessing that the fuel blew up through these holes as there was no fuel streak indicating from where else it may have come.) I pondered on this a bit and then I also noticed the two small spots of diesel under the pass side aft of the rear axle. One of these spots coincides with the drain from the filler door (I think) and the other, I assume, is from where ever the trunk drains. When I drove away, I thought I could see a stream of fuel after I turned right, but when I pulled over I could not confirm this. After I got home (I parked a little up hill with the street crown lifting the driver's side) I removed the filler cap again and fuel started to pour out. I put the cap back on and parked in the opposite direction so that there was not so much fuel resting against the fuel cap.
When I filled, I let the pump switch off automatically and did not top off, which is my normal procedure. When I calculated the mileage I found it to be higher than it should have been (26 something vs my usual 22-23), but since I only fill about once a month (too many vehicles) I couldn't remember whether there had been many freeway miles this last month (which would have easily explained it.) Since the fill, I have driven 22 miles which is what I typically get from a gallon in the city, and that doesn't count what I have left on the streets of Seattle, which I would estimate to be at least a pint to a quart, so far. With the car parked as it is, there is no fuel showing in the neck. I should also point out that the weather has been warm lately, though only in the low 70's today (high 80's on Monday when I filled.) Right now it is about 60F so it's cooled quite a bit.
It seems from the MB manual that there is positive and negative ventilation of this tank and it would make sense that if the tank couldn't exhale it might burp up some fuel, but if I am reading things right, the tank filler should not be able to trap fuel above an air bubble which could then expand in the heat. I'll post more info if I can think of it.

SWjames 08-02-2013 03:36 AM

Oh, also, I should clarify. The drain holes in the fender well are near the outlet of what I assume is the drain hose from the filler door and since I believe (correctly or not) that rainwater blows up through these holes when it's raining, I assume that fuel draining fore of these holes can do the same. Also, when I got in the car today I smelled gasoline (which is strange, it didn't strike me as particularly diesel-like) but as the windows had been up (expecting a thunderstorm) when they are usually down in warm weather, I just attributed it to the the oil dappled cardboard I keep in back to keep the car from marking up my clients' driveways until I get around to replacing the missing oil-drain plug gasket.) The trunk, however, reeked even more than usual of diesel and that's how I came to discover the little pool of diesel in the pass fender well.

SWjames 08-02-2013 03:42 AM

The cap gasket seems to be in good shape in the sense that it would prevent fuel from splashing out, though not from being forced out under pressure. I could not locate the filler neck assemblage in the trunk with a cursory examination. I pulled away the hard plastic liner a little, but it looked like the filler neck was hidden behind a metal body part and I was in a hurry to get home and then to the bank, so I put off a more thorough exam.
It did occur to me that the Benz might have begun to produce, rather than to burn diesel. While this thought was rather appealing, as I might be able to fill my truck's tanks from the Benz's I figured that the engine would probably have to be turning in reverse to accomplish this alchemy and my hopes were dashed by the damning evidence of still having four forward gears and only the usual one reverse gear :-)

SWjames 08-02-2013 03:57 AM

Oops! I also forgot to mention that the car starts and runs pretty much exactly as it always has. Also, I have never had a pressure differential noticeable when removing the fuel filler cap.

Diesel911 08-02-2013 09:56 AM

As your Fuel level in the Fuel Tank Decreases does the leak stop?

Often when I remove My Fuel Fill Cap I here very quick but faint hiss. I don't know if pressure is going out or in.

SWjames 08-09-2013 05:07 AM

OK now the tank is down enough to show less than full and the regurgitating hasn't recurred in about two days. I am afraid to take the cap off, though :-) If the tank was overfilled, was it my fault? Is there something I need to look into maintenance-wise that could have caused it to overfill? It looks like there is an expansion tank associated with my fuel tank and this did happen during very hot weather. Is it possible that the expansion tank is holding fuel when the main tank is low?

Also, as a side note, it looks like I just ordered a new Nissens radiator that is the wrong part number and if I can't stop the shipment in time does anyone with a 1981- 123 300 diesel need a new radiator?


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