Replaced the fuel pump in my 69 Camaro because I had fuel in the oil. After about 10 days there's fuel in the oil again (about a quart) even though the car hadn't moved. There's pressure in the gas tank when I take the gas cap off. Somehow its siphoning from the gas tank into the carburetor?

 

Well, Fuel pump and stuck float are about the only things I know of that will cause gas in the fuel. Check the plugs and see if there fuel on them.

 

Check your gas cap, it should say vented.

 

Ok thanks I replaced the fuel pump and that was my next move just wanted a second opinion

 

You can unhook fuel line to carb and hose it to a container and see if container gets filled.
Gas cap vents in nr directioninward to tank.Ambient temp may be high in causing continued pressure on tank.
Hope there is nop gas water heater in same storage space as Camaro is parked. Don't want fumes igniting .

 

There are two floats (assuming you have a Holley) Gas enters the carb bowl through a needle and seat. As the bowl fills the needle is held close by a float (think commode) . So when the float reaches a certain level the needle is pushed into the seat and no more gas can enter the carb. This setup will work up to 9-10 PSI of fuel after that the pressure will push the needle out of seat and pour gas into your none running engine. It should cause the car to flood and it can fill the oil with gas.

If the needle or seat get varnished by old fuel they can not seal and have the same effect at near zero pressure.

If the float gets stuck or heavy (fills with fuel) it will have the same effect at near zero pressure.

There is one way to be 100% sure the system is not holding pressure. Shove a rag in where the gas cap is. This will not allow more then a pound of so of pressure to build if that and it will keep 90% of the fumes out of the garage because it blocks normal air flow.

In some very rare cases the bowl in the carb could be cracked and allowing fuel into the engine. This would require a bad over heating or the carb being way over torqued when installed.

Also just because a part is new does not mean it can not be defective. I was a GM master tech and many of the problem car I used to get where not hard to fix, someone was assuming that since a part was new there was no way that was the problem.

 

Thank you Gorn
That is my next step.
I have a Edelbrock carb I am not sure if it has two floats but I have to pull it off and take it apart. There is a lot of gas getting in to my oil. About a quart of gas in 10 days just setting in the garage. I do not have a vented gas cap so the pressure is always there. I have had the car on the road 4 years and never had a problem before this year. I do not drive it much only to shows and back. I have only but on about 3000 miles on in 4 years.

So thank you for your help and will let you know what happens.

 

Put a vented gas cap on it, that's what it came with originally. The pressure is pushing the fuel past the needle and seat. With a good vented cap, you won't get that build up of pressure in the tank.

 

No, the vented gas cap that originally came on the car only vents in, not out. It's that way to prevent gas from draining from the lines and back into the tank, purposely keeping fuel in the line. Plus if you have a cap that vents out, gas will squirt out when you accelerate when having a full tank. You don't have a gas cap problem, you have a carburetor issue.

 

Yes that is what I think
Just pulled the carb and gas has been running down the sides of the carb. Car has been on road for 4 years after complete frame off restoration and never had a problem before this. I think it was setting to long and gunked up.