Phew! Cabin Reeks of Fuel!!! 560 SEL - PeachParts Mercedes-Benz Forum

hbofinger · #1 03-28-2003, 10:06 AM

Got a 1989 560 SEL, clean as a whistle, with about 105k miles.

Took it to the gas station yesterday, filled her up, topped her off (I KNOW I should not have done this!).

Parked her in front of the house. Walked by later and smelled gas big time. Wanted to take her for a ride later, opened the door, and though I had filled the cabin, not the tank! Took the TT Roadster instead.

Did some investigation just now. It's definitely coming from the rear (i.e. not the EHA valve or anything in front). Inspected behind the trunk panels - that's when I learned for the first time that the beautiful black leather seat in the back is basically just protective padding for the fuel tank.

I saw no leaks, but did smell a bit of gas.

Could this have happened from just overfilling? All I was able to tell was that all those little rubber tubes and all those accessories to the tank looked 1 day old, not eleven years old.

Any suggestions would be helpful.

Oh yeah - for the experts - just HOW do you remove the metal plate protecting the tank from the junk in the trunk? I removed the three visible screws below the hatshelf, but how is it attached at the bottom? Do I even need to worry?

G-Benz · #2 03-28-2003, 10:31 AM

Your leak may be coming from a fuel hose attached to your fuel pump(s), not the tank!

The pump(s) reside under the car just in front of the passenger side rear tire. The assembly is protected by a plastic cover which must be removed first.

Even a pinhole leak in the fuel hose can wreak odorous havoc!

I had to deal with this twice. A loose hose clamp on the SL fuel hose dripped enough to fumigate the interior, while a leaky one on the W124 didn't drip, but it smelled up the garage after a long drive!

hbofinger · #3 03-28-2003, 10:55 AM

That would be frustrating, especially since I redid that entire area last summer (I did the accumulator and the filter). I will reinspect it, but I doubt that's were it's coming from.

I am still very curious about why it happened right after the visit to the gas station.

G-Benz · #4 03-28-2003, 11:25 AM

Check the tray after you remove it...

...even a small leak over time will leave a telltale residue.

Kestas · #5 03-28-2003, 11:28 AM

I suspect you may have been too aggressive in topping off the tank. Gasoline expands with temperature. We're transitioning into warmer days. The gasoline you pumped was probably chilled from being in the cold ground after this brutal winter. Once it warmed up in your tank it expanded and may have worked its way into the vapor collection system.

Someone told me long ago that fuel injected cars should not be topped off. When you fill up and the hose clicks off, just round up to the nearest quarter if you're paying cash....especially true if you'll just go home and park the car.

hbofinger · #6 03-28-2003, 11:42 AM

G-Benz: Tray is dry. Thanks though. Of course had it some from there I would have been really pissed at myself. Being originally German and, yes, from Stuttgart!, I expect nothing but quality work from myself!

Kestas: I think you've got it. I went back out and checked everything, started the car, etc. Found no traces of leaks or anything.

We have alternating weather here right now, and it was a very nice and warm day following some chillier ones.

There is a spot where the gas could enter the trunk - at the seal for the filler. Even just a small splash would have caused a big stink, so to say.

#7 03-28-2003, 01:30 PM

Henry!! How's it going? Just wanted to chime in and say HI! Haven't had that smell problem on mine so I can't help there. Just curious - how's the idle after putting the filter in your gas line?
Maurice

pentoman · #8 03-28-2003, 03:20 PM

I agree its prbably a combination of overfilling and high temperature

hbofinger · #9 03-28-2003, 04:44 PM

Maurice! How Are Things In The North?

Fuel filter (i.e. bad gas lines) weren't the cause, but I kept the filter in to protect the fuel distributor - I think it's an excellent idea. Soon I will pull it, replace it with an identical one, cut it open, and see what I find inside. This should give me an excellent analysis of the internal conditions of the fuel line. Judging but the shape of other things on this car, I suspect they are in good shape, though.

No, it's a combination of things. Now it's only rough after shutting it down and letting it sit for a few minutes. When you start it cold, it's fine, when it's all warmed up, it's great. So it's either carbon or one of them chips and/or a related sensor. But the car has been behaving so well that I have basically forgotten about the issue.

I did have to replace a leaking EHA control valve.

In terms of the the other responses - I am afraid there still may be a problem, after having driven it 12 miles today. I figured out how to remove the back cover of the fuel tank - the screws on the bottom are hidden by the felt liner. I am going to look over the connection to the fuel filler spout very carefully.

#10 03-31-2003, 09:10 AM

Henry - we had a miserable winter up here. 2 months of -20F - played havoc with all my cars. Then 2 weeks ago it shot from -20 to about 32F and has been hovering there ever since. Celebrated with burgers on the grill!! Felt like summer! Just a note on the rough idle - may help you. After I changed the lines I ran 2 separate fuel treatments (Like tectron) through the tank (translate 2 tankfuls) afterwards and the idle has been perfect ever since - 9 months and counting. Could be some residual crud to get rid of. Cheap and worth a shot.

Southin · #11 07-01-2003, 02:27 PM

On a hot day a week ago I filled the tank only until the normal pump shut-off (I did not knowingly over-fill). I then drove a block to the Wal-Mart lot to get injection cleaner. The black 560SEC was parked in the sun there for about half an hour or more. When I began to remove the gas cap to add the cleaner, about a quarter-pint of fuel squirted out at me. So cold fuel from underground tanks does expand significantly in the sun. No harm to me or the car, though, as far as I can tell.

albert champion · #12 07-01-2003, 07:32 PM

gas cap is the problem. though gasketed, i find that tolerances often prevent a tight enough fit. this allows gasoline to leak out at the fuel filler pipe. once out, the rubber that surrounds the pipe never really furnishes a liquid tight seal, so that small amount of gas will now run down the fuel filler pipe.

as you have learned, that puts gas behind the rear seat. never in large amounts in my experience, but enough to stimulate the olfactory lobe[s] in the interior of the car.

i find this happens most often under hard straight-line deceleration or when performing other high g left turns with the fuel level above half full. i have bought new gas caps, but i find that none of them seal tight enough. perhaps a double gasket will work.

this is a problem that i have been trying to solve for years.

anyone got a fix, i am all ears.

hbofinger · #13 07-01-2003, 08:49 PM

I took out all the interior of the trunk, and I found the same gasoline deposits on top of the right wheelwell (white with brown dots) as I found on the inside of the gasoline filler tube (right by that wheelwell). Seems to me that this has happened intermittently on this car over the years. I checked for leaks and found none (if the gas tank depressurizes with a hiss as you remove the gas cap, you KNOW you don't have a leak, because the air used to pressurize was not able to escape until you removed the cap!)

Temperatures change rapidly here in Washington, D.C. I now never top off anymore, and have had no recurrence of the problem. So I guess the rule is once the pump stops, you stop fueling.

erubin · #14 07-02-2003, 08:48 PM

On some MBs the expansion tank is notorious for gas fume complaints. On SL's which is what I'm more familiar with it's behind the bulkhead in the trunk. No one mentioned checking the expansion tank so maybe it's never a problem with your model.

hbofinger · #15 07-02-2003, 10:50 PM

Right - I don't have the expansion tank, so that was not it. I am just going to stop topping up. So far it has worked....