Gas in oil??
Thread Starter
Instructor
Joined: Mar 2002
Posts: 212
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From: Elko New Market MN
Gas in oil??
Have a 1975 coupe 350 and had motor gone through last summer by a reputable shop. Vette has been parked for winter storage, however I did start it up a couple times. The last time I started it, it ran rougher than hell and was running very rich. Just changed the oil to get ready for spring and almost 9 qts drained!! The oil is very thin and has a heavy gas smell. What the heck can cause gas to get into crankcase???
Thanks in advance for your help.
Bob
Thanks in advance for your help.
Bob
Drifting
Joined: Feb 2002
Posts: 1,987
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From: Manchester, Dead Center in the Middle of TN 25 miles to Jack Daniels,10 miles to Geo Dickle, and .8 mile from the Liquor Store at I-24 Exit 114
St. Jude Donor '05
Fuel pump is not leaking........it's pouring!
The fuel pump diaphragm has burst and is allowing gas to enter the oil pan. Just one of those things that happen in a small block Chevy. j
The fuel pump diaphragm has burst and is allowing gas to enter the oil pan. Just one of those things that happen in a small block Chevy. j
Thread Starter
Instructor
Joined: Mar 2002
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From: Elko New Market MN
Originally Posted by PROSOUTH
Fuel pump is not leaking........it's pouring!
The fuel pump diaphragm has burst and is allowing gas to enter the oil pan. Just one of those things that happen in a small block Chevy. j
The fuel pump diaphragm has burst and is allowing gas to enter the oil pan. Just one of those things that happen in a small block Chevy. j
Le Mans Master
Joined: Jan 2000
Posts: 8,721
Likes: 108
From: Canada
drain it right away and do not start again until you have change oil filter and fuel pump, also check your carb to make sure it is not leaking as well. You don't want to have to totally rebuild that engine.
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Melting Slicks
Joined: Jul 2002
Posts: 3,128
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From: Deltona (son of Deland and DAYTONA) FL
Originally Posted by Bobbyg75
Question was more on changing the fuel pump - any tricks I should be aware of or is it straight forward?
Take your right front wheel off and access the top 2 bolts with an extension through the little slot above the frame. Makes it MUCH easier. That is one of the first tips I learned here in the forum.
Safety Car
Joined: Oct 2004
Posts: 3,725
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From: Minnesota
Originally Posted by isosceles
Take your right front wheel off and access the top 2 bolts with an extension through the little slot above the frame. Makes it MUCH easier. That is one of the first tips I learned here in the forum.
BTW Bob I don't suppose you know of my cousin Jay Maki from Lakeville?
Instructor
Joined: May 2003
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From: Hilton Va
Prob. is the fuel pump, but another way for gas to get into the oil is draining from the carb. Mine needed a rebuild. If I let it run for a while and cut it off, the fuel which had been pumped into the carb would leak,I think, through the needle and seat. Don't know for sure, but just trying to help.
Melting Slicks
Joined: Dec 2000
Posts: 3,407
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From: Carmichael CA
Originally Posted by carhound
Prob. is the fuel pump, but another way for gas to get into the oil is draining from the carb. Mine needed a rebuild. If I let it run for a while and cut it off, the fuel which had been pumped into the carb would leak,I think, through the needle and seat. Don't know for sure, but just trying to help.
The most common reason for fuel in the oil is from a carburator needle valve which is stuck open and causes fuel to pour over the fuel reservoir and down into the cylinders. The engine will run really rough, but it will run because the fuel spilling into the cylinders is in the liquid state and isn't causing too much of a change in the air/fuel mixture up near the spark plugs unless the engine is already hot and it's a hot day.
Checking the carb is easy...just take the fuel line off (plug it so no fuel leaks out), then take a clean hose and attach it to the carb and blow into it...if you can blow into it after the carburator reservoir is full then the carb needs to be rebuilt. You can fill the reservoir manually by pouring fuel into the center of the carb around where the air cleaner stud is located (rochesters).
Thread Starter
Instructor
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From: Elko New Market MN
Originally Posted by Rockn-Roll
Yep. Fuel pump has a "weep" hole in between two diaphrams so that when the outside diaphram blows fuel will leak to the outside...the inside diaphram rarely blows, but if it does then no big deal, until the outside diaphram blows, but if the outside blows then you will see fuel leaking out of the fuel pump.
Racer
Joined: Jan 2002
Posts: 293
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From: Warrensburg, MO
BobbyG,
I had the same problem with my '73 after I replaced a broken rear spindle and the car had set for 4 months. I first suspected the fuel pump, but the real culprit was the fact that I had the car jacked up with the rear significantly higher than the front with a full tank. I discovered this after pulling a few plugs and there was raw fuel in the cylinders. Newton's gravitational force (with an open needle/seat) caused the problem. Just a posibility. Good luck
Jim
I had the same problem with my '73 after I replaced a broken rear spindle and the car had set for 4 months. I first suspected the fuel pump, but the real culprit was the fact that I had the car jacked up with the rear significantly higher than the front with a full tank. I discovered this after pulling a few plugs and there was raw fuel in the cylinders. Newton's gravitational force (with an open needle/seat) caused the problem. Just a posibility. Good luck
Jim
Intermediate
Joined: Oct 2004
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From: Hawaii
I just changed my fuel pump this morning. No big deal, I think you guys had all the pointers covered. I did lose about a gallon of gas, and managed to get some on my head (use goggles). Question - does the oil always get contaminated with gas when the fuel pump blows, or just sometimes? After smelling so much gas today, I can't even tell right now if my oil has a gas smell.
Race Director
Joined: Nov 2000
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From: Waterloo ontario Canada
Originally Posted by Twin_Turbo
leaking fuel pump
Pro
Joined: Oct 2003
Posts: 641
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From: Storm lake Iowa
I had the same thing happen with the stuck carb needle/rear end jacked up...I had gas leaking out around the dipstick sleeve where it enters the block! 
I had to change the oil 3 time before I was happy that it wasn't thin/gassy...Just started and ran for 30 seconds with the fresh oil, then looked at the dipstick. If too thin or gassy smelling, repeat the oil change. You do NOT want thinned out oil protecting your crank bearings!
I had to change the oil 3 time before I was happy that it wasn't thin/gassy...Just started and ran for 30 seconds with the fresh oil, then looked at the dipstick. If too thin or gassy smelling, repeat the oil change. You do NOT want thinned out oil protecting your crank bearings!
Race Director
Joined: Dec 1999
Posts: 16,945
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there's another solution, I use the seals-it seal for my pump on my truck, it keeps the hot oil away from the diaphragm and in case there's a hole in it it'll keep the gas out of the oil. I wonder why no one uses it here...or I have never heard of anyone using them, I've mentioned them a couple of times and they are really worth the money. Can't run electric on my truck as it's a dual tank one w/ a switch valve, I'd have to run another switch valve for the return line so it returns to the proper tank.
Race Director
Joined: Feb 1999
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From: In Dreams There Is Truth Ohio
Originally Posted by Bobbyg75
Question was more on changing the fuel pump - any tricks I should be aware of or is it straight forward?