Gasoline in oil - FINAL

62Ranchero200

62Ranchero200

Famous Member
Fired the Ranchero up today for the first time with the DS2 and MSD 6AL, but I noticed the oil pressure was very low (I didn't drive the Ranchero today, and in fact only had it running at a fast idle for a few minutes).

Checked the oil and it looked strange to me - the level was very high and the oil was very light - so I decided to change it. I have a six quart oil drain pan that I use for changing oil, and that should be plenty since the 250 only takes 4 1/2 quarts of oil, but it overflowed quite badly (by at least a quart).

I noticed that the "oil" seemed very low viscosity and smelled faintly like gasoline. Counting the oil filter, about eight quarts of liquid came out of the engine, almost double the amount of oil that I put in the last time I changed the oil.

I checked the radiator and it's level is perfect, so no water is leaking into the crankcase. Unless I'm forgetting something, it can only be gasoline, and the only source I can think of is a bad diaphram on the fuel pump.

Any other possibilities that I'm overlooking?

Thanks
Bob
 
any puddles on the floor? top of engine?
these would clue U in.

I like ur idea about "@ the fuel pump" but the 2 Qs above need f/u...

keep talkin 2 us...
 
Bob, if you still have a mechanical fuel pump then the diaphram is leaking fuel into the crankcase.
If the engine is running rough it could be a blown power valve.
 
wsa111":296t0jor said:
Bob, if you still have a mechanical fuel pump then the diaphram is leaking fuel into the crankcase.
If the engine is running rough it could be a blown power valve.
Click to expand...

that would be my guess as well.
 
No puddles of pure gasoline either on the floor or on the engine.

Yes, I still have and always have had a mechanical fuel pump. If the diaphragm is leaking gas into the crankcase when running, is the tear in the diaphragm usually visually obvious?

Help me understand how a blown power valve could let gas into the _crankcase_. I can see how it would dump a lot of gas into the intake and make the car run very rich and thus, very rough. But it should still be pushed out the exhaust and not significantly accumulate in the crankcase, right?

Thanks
Bob
 
it can 'w3ash down' the cyl walls past the rings into the crank case

either senerio (I assume) can happen - 1 while running, one while "off".
 
I've replaced many fuel pumps for myself and customers when a pro for exactly that reason - gas in the oil . A carb leak might wash a bit of gas past the rings but not as suddenly or as much as a pump leak . You wouldn't be able to see much of the diaphragm unless torn down and even then there might not be an easily visible tear because it would only open under pressure .
 
This happened rather suddenly - oil pressure was normal (~50-60 PSI at cruise) the last time I drove the car, and the engine hasn't run much since then, just enough to set the timing. Given the brief time and the fact that at least four quarts of gasoline leaked into the crankcase, I doubt that the power valve could be responsible; I suspect the fuel pump.

Thanks,
Bob
 
I think you are lucky, last time I saw a fuel pump diaphragm fail the fuel/vapors that went into the oil ignited in a big explosion that blew the oil cap off the valve cover so hard it dented the hood from the inside! Engine had died (when pump failed) and wouldn't start and the guy was cranking it for a minute or two before the big explosion. No permanent engine damage but I would be surprised if he had pumped in as much fuel as you have, maybe yours went in more gradually and mixed with the oil better?
 
@mustang6,

I suppose "lucky" is a relative term ... yes, I am lucky that there wasn't any explosion; especially since I was cranking the engine with incorrect timing while setting the timing, and I believe the engine did mildly backfire during that process.

On the other hand, the last six or eight weeks have been unlucky in a way ... first the DUI ignition failed and a new module and coil failed to bring it back to life, then it turned out I had the wrong oil pump drive shaft, then a new MSD 6AL was shipped to me without its wiring harness, then finally the gallon of gasoline in my oil.

As far as the gas leak, it does seem sudden in a way as the last time I drove the car, oil pressure was fine and the car ran well - I drove it at least 50 miles. I do keep an eye on the oil pressure gauge so I feel certain that there wasn't much oil in the gas as I was driving it. It seems very coincidental that the fuel pump diaphragm failed at the same time the DUI did, but I can't think of any possible link between the two.

Plan to keep checking the oil often after initial startup, just in case the power valve is the culprit, or is a second culprit, although I don't see how a gallon of gas could wash down the cylinder walls in the short time the engine was running to set the timing (was probably running for 10 minutes or less).

Thanks
Bob
 
"...wash down..."
(from carb)
by that I meant when it wasn't running...
 
Bob, from what you said you are now running the DS11 & the MSD-6AL. Bill
 
Good to know about the pump shaft length. I didn't know that. Your experience with the pushrods for the adjustable valvetrain helped me. Good info.
 
Yeah sorry, didn't mean to imply you were "lucky" to have all those problems. I do think you have some reliability to look forward to with the DSII/MSD combo, I have run those together in I6 and V8 cars for over 10 years with no problems.

On the oil/fuel issue I just don't see how that could have all come through the carb unless you had an electric fuel pump that kept running after the engine was off. Reason is all that fuel would have to go through the carb, down the intake, past the valves and rings and into the oil. With a mechanical pump most all of that would have to happen while the engine was turning/running and if that were happening in huge way, it couldn't run because that pathway is through the (supposedly firing) combustion chambers. Unless you had an electric fuel pump pumping fuel when the engine was off, it would flood or explode through the intake before filling the crankcase when the engine was running. So extremely unlikely, almost impossible on a running engine with a mechanical fuel pump I would say.

The two other options are fuel through the fuel pump diaphragm or (unfortunately) coolant, which has many opportunities to leak into the crankcase. I don't want to insult you with what to look for on the latter, but lightish, runny, almost aerated-looking (fluffy) oil is a sign of water in the oil. In fact a little coolant will "fluff" air into the oil that will make it gain much more volume than you look like you loose from the cooling system. So its not a 1:1 loss/gain between the oil and coolant.

Either way, the detective path is the same. Drain out all the oil and replace with a know amount of fresh oil, replace the fuel pump and run it again. If the same thing happens, get the coolant system pressure tested and oil sniffed for coolant. I hope that's not it but I've seen that much more commonly than fuel issues. Head gaskets or cracked block or head are the most common cause of that.

Best of luck, Scott
 
mustang6":2j32ryxs said:
Yeah sorry, didn't mean to imply you were "lucky" to have all those problems. I do think you have some reliability to look forward to with the DSII/MSD combo, I have run those together in I6 and V8 cars for over 10 years with no problems.

On the oil/fuel issue I just don't see how that could have all come through the carb unless you had an electric fuel pump that kept running after the engine was off. Reason is all that fuel would have to go through the carb, down the intake, past the valves and rings and into the oil. With a mechanical pump most all of that would have to happen while the engine was turning/running and if that were happening in huge way, it couldn't run because that pathway is through the (supposedly firing) combustion chambers. Unless you had an electric fuel pump pumping fuel when the engine was off, it would flood or explode through the intake before filling the crankcase when the engine was running. So extremely unlikely, almost impossible on a running engine with a mechanical fuel pump I would say.

The two other options are fuel through the fuel pump diaphragm or (unfortunately) coolant, which has many opportunities to leak into the crankcase. I don't want to insult you with what to look for on the latter, but lightish, runny, almost aerated-looking (fluffy) oil is a sign of water in the oil. In fact a little coolant will "fluff" air into the oil that will make it gain much more volume than you look like you loose from the cooling system. So its not a 1:1 loss/gain between the oil and coolant.

Either way, the detective path is the same. Drain out all the oil and replace with a know amount of fresh oil, replace the fuel pump and run it again. If the same thing happens, get the coolant system pressure tested and oil sniffed for coolant. I hope that's not it but I've seen that much more commonly than fuel issues. Head gaskets or cracked block or head are the most common cause of that.

Best of luck, Scott
Click to expand...

@mustang6,

I did check the coolant and it was absolutely full; it may not be a 1:1 loss/gain but the radiator would have had to have lost at least some level to have an extra four quarts of liquid in the crankcase. In addition, the oil was not aerated at all, and smelled faintly of gasoline.

@wsa11,

Yes, the engine starts acceptably well now with the DS2 and MSD 6AL; but with low oil pressure I didn't dare to run it very long, certainly not long enough to warm up. Now that I've changed the oil and fuel pump, I'll start it again and warm it up when time allows, then check for gas in the oil again.

Thank you,
Bob
 
Last Saturday, I drove the car to my local cruise-in and back - about a 30 mile round trip. The car ran very well, and after returning home there's no trace of gas in the oil. So, it appears that the fuel pump diaphram was indeed the culprit.

Thanks
Bob
 
Drain that oil and change filter again after a hundred miles or so to remove any residual soaked in gasoline and the internal sludge , varnish , etc. that most likely was loosened by the gasoline {excellent solvent you know} and contaminate the oil .
 
:beer: congrats! Now hope you can enjoy many miles of trouble free driving. Good luck :nod:
 
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