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JAM
New User
Sep 27, 2007, 6:29 PM
Post #1 of 9
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91 Caravan--gas in oil
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Have a 91 Caravan SE AWD with 2.5L 4cyl. Only 60,000miles. Most drive to work and short distances. Other day had to accelerate rapidly to avoid car. A few miles down road I note loss of oil pressure. I checked oil and it was diluted with gasoline. This van has electric fuel pump so I don't think it is a fuel pump diaphram problem. Engine starts up well and runs well. Is the problem possibly associated with emission control circulation system. Help! Thanks.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Sep 28, 2007, 4:26 AM
Post #2 of 9
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Re: 91 Caravan--gas in oil
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Brain teaser?? The fuel pump isn't near the crankcase and oil so that's not it. The old ones on engine (mechanical) could do that and did.
So that leaves the fuel injection overloading the combustion chamber which could leak down thru piston rings into crankcase but at that level of raw fuel would smoke while running and run VERY poorly. Other point of contact is vapor recovery system (emission control system) which should burn off as it is sent to the intake manifold. Again that would flood the engine if that excessive so this is a tough one with what you noticed??
T
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JAM
New User
Sep 28, 2007, 5:43 PM
Post #3 of 9
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Re: 91 Caravan--gas in oil
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Certainly has me baffaled! Changed oil and regained oil pressure but in short order loss again and heavily diluted with gasoline. Is there a fuel tank vent line running back into the crankcase? Is there a check valve in the emission control circuit?
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way2old
Veteran
/ Moderator
Sep 28, 2007, 6:15 PM
Post #4 of 9
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Re: 91 Caravan--gas in oil
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Sounds like you have an injector that is stuck open. Have you noticed the vehicle running rougher?
Being way2old is why I need help from younger minds
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Sep 29, 2007, 12:51 AM
Post #5 of 9
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Re: 91 Caravan--gas in oil
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JAM - w2o, could this be a carbed engine? I recall a Caravan and forget what year that was all Mitsubishi I think and had a fussy carb. It had to an 80s model year - perhaps 1986. I would think that about ended carbs near that year.
That one had all kinds of carb problems and customer had no money for a new one. It idled way too high as I recall but not overfueled. He found a used one and with the two I made one that behaved is all I remember now.
IT MAY HAVE HAD A MECHANICAL FUEL PUMP and that would be able to flood out the oil with the engine still running well until oil was too full or too thin as noticed with this one.
Just a note: When you think they "never" did something with a vehicle - sure enough the exception comes along. One was a car with points long after electronic ignition took over and finally failed due to never being replaced, adjusted or anything for perhaps 75K. That was an Audi engine in an AMC Concorde I believe done that way from the factory!!
T
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JAM
New User
Sep 29, 2007, 7:00 AM
Post #6 of 9
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Re: 91 Caravan--gas in oil
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This is a fuel injection engine. If the injector were stuck open, I don't think that the gas/oil dilution would be so quick. What do you think? And wouldn't there be raw fuel coming out the tail pipe...white smoke??
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Sep 29, 2007, 7:49 AM
Post #7 of 9
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Re: 91 Caravan--gas in oil
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What's odd is this doesn't seem to be burning the fuel but leaking it into oil. If it burned it, much would get burned and hurt cat converter(s) and would show as BLACK smoke or soot in tailpipe. WHITE would be anit-freeze or water vapor normal in some cold conditions.
Does this have an on engine machanical fuel pump somehow? You stated that this happens quickly and if that much fuel got into the combustion area it would run like crap which you said it didn't. At the rate you notice the oil pressure going down this is fast and I'm surprised you haven't found this with hydraulic lock from a soaked/filled cylinder with fuel that can't compress the liquid.
The evaporative emissions do get burned. Same thing there though. It would run like crap at the rate you are mentioning. You should have a "service engine soon" or "check engine soon" light blaring at you but it wouldn't pick up on that if running well and gas just gets in the oil - at least till oil pressure got so low you'd get a warning on that.
There was a VolksWagon that used a mechanical fuel pump with the air cooled four cyl that had this problem ages ago on me. That is simply the only one fuel injected car with mechanical fuel pump on engine that I've ever noticed. I wouldn't generally study every car that I ever touched for all details untill it was a service item or problem existed.
I simply can't see how this could be anything but a mechanical fuel pump diaphragm leak with the speed of this happening AND it running OK????????????????
Perhaps way2old has seen this happen as you have described with just leaking fuel injector(s) but I haven't so I'm lost with this?? For oil dilution to cause low oil viscosity would take a fair amount of raw gas. How overfull are you finding this? This will destroy the engine if left unfixed - of that I'm pretty sure,
T
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JAM
New User
Oct 7, 2007, 2:55 PM
Post #8 of 9
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Re: 91 Caravan--gas in oil
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Can you tell me how the fuel pressure regulator works and how it might be responsible. If the diaphragm in that regulator were to break, is it possible that fuel could be entering the engine block in that manner?
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Tom Greenleaf
Ultimate Carjunky
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Oct 7, 2007, 4:10 PM
Post #9 of 9
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Re: 91 Caravan--gas in oil
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In an electric fuel pumped system pressure would be senses in the line from the fuel pump or at it (in it) and the electric power to the pump shuts off at a set pressure by a spring on a diaphragm. It is not placed such that would leak into crankcase. Machanical fuel pumps are also a spring and diaphragm - fuel on one side and the arm to crankshaft is exposed to crankcase area and that even mists the mechical arm to lube it. That diaphragm can leak right into the crankcase and fast!
You need to look at all the lines that carry fuel or fuel vapor which will include the vapor recovery system which does hold fuel vapor in charcoal and it burns it off. I guess if that got flooded with raw fuel it could be a problem but it would still be on the intake side of engine not in the crankcase directly but if enough could leak past piston rings into crankcase same as a badly leaking fuel injector could. That would take a lot of fuel leakage and engine would run like crap and smoke black or if really bad hydraulically lock the engine which cannot compress a liquid.
This is about raw fuel getting into the crankcase directly if the engine doesn't show that it is choking on raw fuel in the intake side. That's it. It's not coming from your sun visor - this can only come from fuel under pressure at the engine. I'm not there so look at it so you have to :-)
T
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