M103 crankcase full of fuel
 

Just picked up a 1988 300E, runs great but in the coarse of 3 weeks the crankcase has filled up with fuel mixing in with the oil.....Drained the oil and approxiamtely 12 US Quarts came out!!!....What could possibly be causing the fuel to bleed into the crankcase.......When I got the car 3 weeks ago the oil level was normal!....Thanks in advance!

That amount of fuel will ruin the engine if it hasn't already. Whats the fuel mileage like and does the engine run OK? Stop driving it until you fix it!

Gilly

The source of fuel in the crankcase shouldn't be much of a mystery, just think like a gas molecule. After getting mixed with air and pressurized into the the cylinder, the biggest escape route is geting past the piston rings in at least one of the cylinders and then down into the crankcase. The only other avenues of escape are in the valves, which would lead upwards to the camshaft and valve cover area, where mixing with the oil would take you back down to the crankcase.

M103 Crankcase Full of fuel
 

Gilly, I just removed the air filter and it looks like it hasn't been changed in many years, almost completely clogged....My question is: "Would the restriction in airflow cause the fuel to not atomize as well, thus causing excessive liquid fuel buildup in the cylinders?".........The car runs GREAT but the fuel consumption is extremely excessive in comparison to my 1987 300E....Thank you!

The fuel pressure regulator may have a leak. Check the vacuum line for fuel.

First I would pull the vent off the valve cover with the engine running and of course fresh oil in it! If you hear and feel a ton of air flowing out of there you most likely have bad valve seals! Where gas flows so will air. Next of course check the fuel regulator by pulling the vacuum line on it and make sure no gas is pouring out of it. That leads back to the intake and through the same rubber hoses that go back to the valve cover vent on my M102 motor and I guess could flow back into the valve cover. Last is the big one and the most likely problem, that the rings on the pistons have lined up and the gas is going straight to the oil pan! That would mean removing the head and checking the rings for alignment. It happens unfortunatelly and of course means new rings! Good Luck!

You can not check piston rings by only removing the head. You also need to remove the pistons. Raw gasoline can not escape by the valve seals. Gasoline must first go through the valve seats and then exit through the exhaust system.
Possible causes of your problem:
* badly leaking fuel injectors
* Cold start valve always on due to defective temp. sensor or valve.
* Replace your air filter.
* Fuel regulator.
You said "the car runs great" That would indicate (altough not totally) that the rings are just fine and that there is no major bypass at the valve seats.
Check you fuel/vacuum system from a to Z first.
jackD

Check the fuel-related items listed above for problems. Then have a leak-down test performed on the engine (as opposed to a compression test); leakdown will locate carbonized rings or a broken ring, either of which is possible while still allowing in certain instances the car to run OK

I had the same problem with a Alpha Romeo Spyder. I fact the girl I got it from, had been told that the engine was shot and would require replacement. So I got the car VERY cheap. It turned out that the last set of plug wires that had been installed on the engine di not have the copper tips installed on the distributer end and this cause a whole lot of arcing. The engine was plum full of gas. When drained and refilled and a new set of wires installed it ran like a dream. It was also a super clean engine at that time.

Sure you can, poor a liquid of your choice in there and see if it drops in level. Cheesy way of doing it but it will work! Also as suggested a leak down test will tell you a hell of a lot as well.:D

Edit: Just a question! How does the fuel get into the oil from a start valve leaking? I would think you would just be getting extra fuel into the intake and thus into the chambers and the car would run worse due to being more rich then normal! Am I wrong in this thinking?:D

The super-rich fuel mixture is not completly burned and the excess gas washes the cylinder walls. Some fuel drains down past the rings and settles in the oil sump. The washed cyl walls, and rings, also wear the cylinders.
That's my story and I'm sticking too it.

Sounds good to me!:D

Right on the button.
Excess fuel from: leaking injectors, cold start valve, clogged air filter, faulty fuel regulator.

Most likely cause is a bad fuel pressure regulator dumping fuel into the valve cover through the "overflow" line. This is very common on Volvos.

You will blow the engine up eventually if you don't solve the problem, the vapors can ignite (yikes!!!). Not as much fun as blowing acetylene into a tired deisel, but still fun!

Pull the hose off the pressure regulator, chances are it's full of fuel.

The other other way fuel can get in there is through the cold start valve, the KE-Jet won't run that rich.

Peter

Not to put too fine a point on it, but CIS injectors always 'leak'.