Oil Smells Like Gas

[JFawcett]

1987 560SL 98,000 miles.
Was checking the oil yesterday and noticed it was about 1/2 quart low....don't know what posessed me, but I smelled the dipstick and it smells like gas. Car is running great, but don't want that to change.
I have had all needed services done to the car - timing chain, etc.
Do I have something fatal here?

[KCM]

Sounds like it may be flooding a little and leaking gas past the piston rings. Nothing fatal, but if the oil gets too saturated with gas, it will hinder proper lubrication of the engine by thinning the oil. Gas is more of a cleaner than a lubricant. Do you drive it on short drives? Short drives where you start the engine and the engine does not get up to full operating temperature for an extended time may dump excess fuel into the cylinders. With short drives you should be changing the oil more often anyways, I would say every 2000 miles.

You may also have a leaking injector. From what I've learned, and I am no expert yet, there is suppose to be a low residual fuel pressure at the injectors when the engine is off, at least for several hours or days. The injectors act like a valve which opens at a certain pressure built up by the electric fuel pump and continuously sprays fuel into the intake of each cylinder while the engine is running. If this a correct, and an injector is leaking, it will dump all the low pressure and fuel into the cylinder after the engine is shut off. This would definitely be a source for the fuel smell. I would run a couple bottles of fuel injector cleaner through the car to clean out any gumming that may have occurred in the injectors.

[Roncallo]

Your injectors may be leaking down. You need to do a fuel system pressure test.

John Roncallo

[GSMITH]

You might want to check the fuel pressure regualtor vent tube.
It goes from the driver side of the intake to the passenger side valve cover. If you take it loose from the valve cover and it drips gas you need to replace the regulator. Not a bad DIY job.

[JFawcett]

Thanks....can you provide some additional details on the fuel pressure regulator vent tube? Also, where is the regulator?
Thanks!

[GSMITH]

Here is where you can see what it looks like.
http://catalog.worldpac.com/mercedesshop/sophio/quote.jsp?clientid=catalog.mercedesshop&cookieid=21V0I9EQT23M0SD3GI&baseurl=http://catalog.peachparts.com/&partner=mercedesshop&year=1986&product=C3000-26937&application=000046302

I do not remember spending that much but it is about the same price at the sites I use to compare prices. If you click on the part you will see a small rubber hose on one end. This is the vent side. Once you remove the air cleaner housing look on the driver side and you will see it. There will be a hard plastic tube running from it to the passenger side valve cover.

If you check the line at the vent hose for the passenger side valve cover soon after turning the motor off and it drips gas (put a rag under it) you have found your problem. If this is your problem change the oil after you replace the regulator as the gas will thin out the oil.

It went bad on my 86 560 sl last year around the same mileage. It took me awhile to find and fix it and my 20W50 oil was really thined out.

It does not take long to replace. Just take your time and have rags under it to catch the gas that will come out.

[JFawcett]

Thanks. I will check this weekend.
Do they rebuild these things or is this another pride of ownership situation?