Oil level extra full

Wanted to do some Spring work with my JD 420 and after letting it sit all winter I checked all the fluid levels.  Gas empty, coolant down just a bit, hydraulic fluid ok.  Then I checked the dipstick for oil level---over full by at least a quart.  Now I know I didn't overfill it at the last change and I hadn't added any.  The color was black so I figured I had better change it and see if there was anything obvious.  The oil that came out was thin, black and smelled like gasoline.  So my questions are: 1) Is there a way that gas can leak into the oil?  and 2) If I have coolant leaking in would it be obvious--smell, looks, or separation?  Thanks in advance for input.  Jerry 

I didn't shut off the fuel at the sediment bowl because when I used to do that it would leak at the shutoff so I left it on.  Maybe I just need to fix that.

Eldon (WA) wrote: My wife's 520 has an automatic fuel shutoff on it to keep the gas from running into the crankcase and also shuts the fuel off if there is no oil pressure.  I'm not sure if the 420 used a similar setup or not, but the first spring we had it I went to start it up and it shot oil/gas out of the breather tube because it was way too full. I had to take the safety shutoff apart and put in new rubber diaphrams. It has never leaked into the crankcase since.

Does this system bypass the float and seat? I'm a novice, but from my limited experience, if the float is adjusted properly and the needle and seat seal when the float rises to the proper height, gas cannot get into the engine.

The 520 fuel shut off is near the transmission and separates oil from gasoline only by that rubber diaphragm. When the diaphragm leaks it puts gasoline from the gas tank into the oil.

Gerald J.

I lost a Ford truck engine that way about 13 years ago when the fuel pressure regulator diaphragm split and filled the engine with gasoline through the vacuum lines. It was the first year of a fuel injected V-8 and the regulator leak didn't drop the pressure because it didn't have the big secondary fuel filter. When it filled a couple cylinders it made it hard to crank destroying starters. And ordinary fuel line pressure checks didn't hint at the problem, the shop working on it ignited the engine compartment. After they fixed it, it ran with a definite rattle like piston rings bang against each other from having smashed the ring separation ridges away. They changed oil twice and found bronze in the drained oil.

Ethanol probably sped up the failure of the oil pressure operated fuel cutoff in the JD tractor, but they are older now than rubber usually lasts.

Gerald J.

I installed a small 1/4" ball valve in the fuel line when my Troy Built started filling the cylinder with fuel, yes I could have fixed the float , but this was easier.