gas odor inside - PeachParts Mercedes-Benz Forum

woody loller · #1 01-13-2008, 09:20 PM

Everytime I open the door and climb in my 1986 560 SL I detect a slight gas odor. After starting up it seems to disappear or maybe I just get used to it. I can't find signs of leakage on any thing on the engine or back on the fuel pump area, no gas odor when I open the trunk. Any thoughts?

Alkraut · #2 01-13-2008, 09:42 PM

Sniff around under the air cleaner, and by the fuel injectors. There is a rubber hose system that connects to the injector holders. If the hose has cracks or holes you may get some static fumes. Best time to check it is after the car has sat awhile, and before you start it up. There are also molded rubber seal donuts around each fuel injector. One or more may be brittle/cracked.

Dusty4 · #3 01-13-2008, 09:47 PM

If your car is like our 75, there are also rubber lines between the fuel tank and filter, below the fuel tank that get rotten.

Roncallo · #4 01-13-2008, 11:09 PM

If you cant find anything obvious, Replace the fuel cap.

Been There Done That

John Roncallo

meltedpanda · #5 01-14-2008, 11:01 AM

mine went away after I redid all the rubber vent lines on the gas tank. I think there was 6 or 8 connections

Got to take off the back panel in the trunk to access

woody loller · #6 01-14-2008, 07:44 PM

Thanks everyones for your comments. The fuel injectors and seals are new but I will need to look closely at those hose. The gas hose from the tank is new as are the fuel pumps filters and conmnecting hoses. Does anyone known how long the gas cap should hold pressure? I hadn't though about hose little hoses on the gas tank, I will probably change those out. I report back when I have results. Thanks Woody

rocky raccoon · #7 01-15-2008, 07:34 AM

Sorry for the late post but I hope it is still useful.

When I first bought it my 1988 560SL had a fuel odor until startup and driveaway. There also was no evidence of a leak. In my case the problem proved to be the metal gaskets on both sides of the banjo bolt fitting at the fuel pump output. It would not leak unless the pump was running and producing pressure. I did not find the problem until I crawled under the car with the engine running.

The previous owner apparently reused the aluminum gaskets after changing the fuel filter. I replaced those gaskets and problem solved. The gaskets are available in aluminum or copper. I recommend copper and don't overtighten and don't reuse. They are cheap enough.

The bonus was improved mileage since I was not spraying the world with gasoline while underway.

meltedpanda · #8 01-15-2008, 11:09 AM

good point, I had a small leak there as well, easy to change out lines. Mine was old rubber and cracked
If you never did the vent lines on the tank, I would say that is where your trouble lies
These lines also vent to the outside and it just hangs under the car, somewhere above the rear axle. it could be clogged or caked with crap and not letting the fumes escape to the air

donbryce · #9 01-15-2008, 02:20 PM

There's a charcoal canister tucked up under the front of the left front fender, only visible by peering up from underneath, under the valence by the left lower corner of the radiator/air intake scoop. Don't know if this is your problem, or one of the lines to/from it, which I think are for vapours from the tank.

Roncallo · #10 01-15-2008, 07:48 PM

Before you spend too much money. I replaced every line in the car. I pulled and tested the charcoal canister. I was about to order a charcoal canister anyway thinking it was the only thing I didn't replace aside from the tank itself. Then I got this bright idea. A cap was another part I didn't replace and it was only $15.00 verses $135.00 for the canister. I got the cap and the problem was solved. There was nothing obviously wrong with it. Sometimes a shotgun approach is the way to go if its cheep enough.

By the way, replacing every line in the car is a good idea they are 20 years old. A friend of mine purchased a Ferrari 308 GTS, fire job caused by old lines.

John Roncallo

aam · #11 01-15-2008, 09:27 PM

Quote:

Originally Posted by Roncallo

Before you spend too much money. I replaced every line in the car. I pulled and tested the charcoal canister. I was about to order a charcoal canister anyway thinking it was the only thing I didn't replace aside from the tank itself. Then I got this bright idea. A cap was another part I didn't replace and it was only $15.00 verses $135.00 for the canister. I got the cap and the problem was solved. There was nothing obviously wrong with it. Sometimes a shotgun approach is the way to go if its cheep enough.

By the way, replacing every line in the car is a good idea they are 20 years old. A friend of mine purchased a Ferrari 308 GTS, fire job caused by old lines.

John Roncallo

Ifyou dont want to replace the cap.
They have replaceable washers.

pwrslider · #12 01-15-2008, 11:48 PM

I have a 72 350sl....I too have noticed a gas smell in the interior....I changed out all of the lines, the gas cap and the charcoal canister.......still smells....like an old car with mild gas smells...

My mech. is stumped as well........................

WIll get back to it as spring approaches..and will let you know what it is..

..one other thingy...my tranny is leaking at the front coupler / gasket....one small drip looks like a pint....but levels dont ever go down that much. The problem is that the fluid hits the forward exhust crossover....and puffs to a smoke during running temps. My mech wants to change the whole tranny...but everything still works fine...and shifts OK...will wait until it go out...and until then..add fluid once a year or so...

woody loller · #13 01-16-2008, 08:39 PM

Thanks for the additional posts guys, with the help of everyones advise I will investigate this problem further this weekend (if its not to cold!) and report back. Woody

GSMITH · #14 01-19-2008, 11:17 AM

On my 86 560sl it took me quite a while to find this one. My only hint was when I removed the oil fill cap the gas odor got worse.

How to check the fuel pressure regulator vent tube. It is a hard plastic line that runs into the rubber hose that connects at the rear of the passenger side valve cover. If the diaphram goes bad it will slowly dump gas into the engine so you will never see a leak. With the fuel lines under pressure if you pull out the hard line out of the rubber hose and it drips gas you will need to replace the regulator and oil ASAP. You may need to check it at the regulator itself if the hard line is disconnected at that end.

I was lucky and only got a good internal engine cleaning. Others have not been so lucky and have ruined bearings because the oil got to thin.

woody loller · #15 01-24-2008, 08:54 PM

Spent a good part of the day investigating this gas odor. I checked the fuel pressure regulator vacuum line and found no leakage under pressure, checked all the other lines around the injectors all were ok. Did find a break in the charcoal canister line and fixed that. Also pulled the back of the truck out and replaced all the small gas lines on the gas tank. Still have the gas odor. I will go for a new gas cap next and see if that does it. Will post back when I can get my hands on one. Woody