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4.0L, gas in oil?

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What are some of the things to check for gas in the oil. The truck runs just fine, but after running it on a few 100 mile trips I went to check the oil and it was way above the full mark and smelled like gas. Like I said the truck runs real well, and doesn't overheat or anything... Its also got newer ford motorsports 19# injectors, but it did the same thing with the old injectors.


Any idea's?

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This happened to me once with a 1939 Hudson I was restoring -- but that had a mechanical fuel pump on the block and the internal diaphragm ruptured. I can't think of any way that much gasoline could get by the rings in a fuel injected system, unless the injectors aren't functioning right and the system is pumping way too much fuel. How old is the oxygen sensor? Have you had the truck scanned to see what kind of readings the O2 sensor is sending to the ECU? The only thing I can think is that it's running in open loop mode and sending too much fuel, all the time.


It isn't safe to drive it that way. Get it checked.

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I don't believe its blowby, wouldn't the motor have poor compression then? Its not like a little gas, it read a good 2 inches past the full mark on the dipstick...



You did a compression check?


Does it fire on all cylinders? Pull the plugs and see if they're wet. If it doesn't, that can cause problems.



I've seen engines with the oil level creep up due to blow-by. Not as bad though. Anyways, the PCV system is supposed to burn off all that crap, but that never really happens. Not that it would account for that much.


FWIW, despite gas being really useless for the oil, I bet the motor will be okay for quite a while. These things seem to be tough enough...

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o2 sensor is on the exhaust pipe so thats out the question. as for compression if you have a warped cylinder yes gas can leak but it would obviously still rin just on like 5 3/4 cylinders. so id go to nape or grab a compression checker and check compression on all your cylinders. also check the vacume/breather that comes off the block and see if gas iis going in there. hopefully its not a vavle :headpop:

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I checked the compression a while back when we first got the truck, it was pretty good, I can't remember the numbers. And its firing on all 6, it runs great and has plenty of power....


i'm going to recheck the compression but I don't think thats the problem.

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o2 sensor is on the exhaust pipe so thats out the question.

Out of the question? Are you joking? The O2 sensor is the sensor that reads the percentage of unburned hydrocarbon in the exhaust and controls the amount of fuel the injectors squirt. A dead O2 sensor results in an engine that runs super-rich, all the time.


I'd say that's FAR from being out of the question. It is, in fact, a very likely suspect.

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the o2 sensor helps input CONTROLS to the fuel system.


if it is reading WRONG then you better believe that he's running rich.


re-read the previous statement to yours, it should make sense because he is 100% spot on right.

he is indeed correct.


I would also cheack that you've not got an injector that's stuck open.

A stuck injector would allow a lot of gas into the cylinder, even when the motor was off.

Pull the spark plugs, and look to see if one looks a lot different than the other.

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There is no fuel going into the exhaust, I know that much. As far as the injectors go, there is no change from the original injectors to the new ford motorsports 19# injectors we put in. Also, I've had 02 sensors go bad and it created a very bad problem with the motor running rich, which in turned cause it to run poorly and created alot of smoke through the exhaust. i'm still putting in a new sensor tho as its cheap enough and a good idea as they gradually loolse performance.


At this point its all purely speculation as I don't have time to check it out. But the truck runs good, does not have smoke from the exhaust, and doesn't exhibit any characteristics of running rich. So just from that info, what does that leave?


1. After its shut off the presurized fuel from the fuel rail leaks into the cylinders and gets past the rings into the crankcase


2. Fuel is entering the crankcase while it is running from somewhere else, ie the vacuum system


3. There is just enough blow by in the rings to let fuel by but not oil into the combustion chamber.


Anything else?? Once I have time to start actually looking at the truck i'll be sure to post my findings. First thing would be a compression test, then I guess a leak down test of the fuel preasure in the rail....[/b]

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