My old (now my moms) '88 W126 suddenly started smelling like gasoline on the interior a few days after the last fill-up a couple of weeks ago. I took it and filled the tank (we try to keep it filled up since the gauge is inaccurate even after spending $700 to get it repaired a couple of years ago).

Anyway, the car didn't smell like gas that day... it wasn't until about 3 days later when I went to get something out of it that the interior reeked of raw gasoline fumes... as well as the trunk. There are no leaks anywhere.

I always top it off (which I shouldn't and will not again). I thought maybe something was wrong with the seal on the cap, so I removed it and gasoline started GUSHING out of the filler hole. The car was setting with the right rear being the lowest point however, so I guess that is normal, lol. There was no gasoline seeping out of the cap however.

I didn't get to look at the seal due to the gas pouring out, so I had to put the cap back on posthaste. Does this sound like a bad gas cap seal causing the odor inside the car, or does it sound like something else? Is there a trouble spot on these cars that allows fumes to enter the passenger compartment, but with no visible leaks? I am hoping it is as simple as needing a new cap.

Thanks!

If that engine has an EHA valve remove the air cleaner assembly and check for gas weeping from the black plastic body. Best to check when the engine is cold because a hot engine will cause the weeping gas to evaporate quickly. With a cold engine turn the key so the fuel pump(s) run and closely inspect the outside of the EHA valve for wetness.

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Fred Hoelzle

I would start with replacing the sealing sleeve below the cap. Even if the cap seal is leaking the sleeve should prevent gas entering the trunk.

A leak in the fuel system itself (AHA valve and fuel pressure regulator) give a continuous fuel smell if the engine is running.

The w126 has a fuel evaporation system to catch fuel vapors. It releases the pressure, but only with an engine temperature above 50C and throttle valve above idle speed. So if driving short distances fuel pressure in the tank may build up.


Rob

Thanks for the replies.

Well the EHA valve was actually replaced about two years ago. When it was leaking, we had a fuel smell in the engine compartment. This time there is no smell at all in the engine compartment... it is strictly in the passenger compartment and trunk.

Yeah, the tank definitely has pressure. When I try to remove the cap, fuel literally gushes out and what runs down that drain hole under the cap makes it to the ground. How do you replace the sealing sleeve below the cap?

Thanks!

In theory pry it out and put a new one in (from the outside).
If you still have the original one it will be less flexible than a new one.
A bit of soap makes is easier to put the new one in.

The W126 has an upright tank (against the rear seat) and the filler neck is only slightly higher than the top of the tank. It is very important not to overfill the tank.

Fuel should not gush out if you remove the cap, unless you park on a very steep incline.
It sounds like you overfill the tank. These tanks have a overfill protection, a small tank inside with small holes in it, this prevents overfilling. If you fill the tank completely, wait a few seconds, and top it up again, you bypass this protection and overfill the tank.

Rob

Yeah I filled it up that night until it would hold no more! Reason is, the gauge is inaccurate and we try to keep it filled. One of our local supermarkets has a gas station and offers "fuel bucks" where you get .15¢ off per gallon for every $150 you spend. Well we thought the car was low on gas, but it only used 5 gallons of gas, so we (or I) was trying to get all of the gas we could with our discount. I guess I went overboard... maybe nothing wrong with the car at all and I simply overfilled it?

Thanks again!

I had something similar happen years ago with our 300e. Someone pumped gas and we had a gas smell from the trunk that entered the cabin. After replacing the rubber gasket between the filler neck and the body and removing the trunk interior to look for leaks none were found and smell was still there. I got rid of the smell by taking a bucket of soapy water and a rag and washed the inside of the trunk. Smell never came back

Thanks! Well that may be our issue and partly that I overfilled the car. I moved the car this evening when I got home from work... I turned it around where the right rear of the car would be the highest point of the car. I removed the cap and nothing spewed out and now the car does not even smell like gas on the inside. I think that sleeve is bad though, as it looks a little dry-rotted.

Thanks again for all of the help!